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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>Argyll Usage Scenarios</title>
    <meta http-equiv="content-type" content="text/html;
      charset=windows-1252">
  </head>
  <body>
    <h2><u>Typical usage Scenarios and Examples</u></h2>
    Choose a task from the list below. For more details on alternative
    options, follow the links to the individual tools being used.<br>
    <br>
    Note that by default it is assumed that ICC profile have the file
    extension <span style="font-weight: bold;">.icm</span>, but that on
    Apple OS X and Unix/Linux platforms, the <span style="font-weight:
      bold;">.icc</span> extension is expected and should be used.<br>
    <h4><a href="#PM1">Profiling Displays</a></h4>
    <h4>&nbsp;&nbsp;&nbsp; <a href="#PM1a">Checking you can access your
        display<br>
      </a></h4>
    <h4>&nbsp;&nbsp;&nbsp; <a href="#PM1b">Adjusting and Calibrating a
        displays</a></h4>
    <h4>&nbsp;&nbsp;&nbsp; <a href="#PM1c">Adjusting, calibrating and
        profiling in one step<br>
      </a><span style="font-weight: bold;"></span><span
        style="font-weight: bold;"></span><span style="text-decoration:
        underline;"></span></h4>
    <h4>&nbsp;&nbsp;&nbsp; <a href="#PM2">Creating display test values</a></h4>
    <h4> &nbsp;&nbsp;&nbsp; <a href="#PM3">Taking readings from a
        display</a></h4>
    <h4> &nbsp;&nbsp;&nbsp; <a href="#PM4">Creating a display profile</a></h4>
    <h4> &nbsp;&nbsp;&nbsp; <span style="text-decoration: underline;"></span><a
        href="#PM5">Installing a display profile</a></h4>
    <h4> &nbsp;&nbsp;&nbsp; <span style="text-decoration: underline;"></span><a
        href="#PM6">Expert tips when measuring displays</a></h4>
    <h4>&nbsp;&nbsp;&nbsp; <span style="text-decoration: underline;"></span><a
        href="#PM7">Calibrating and profiling a display that doesn't
        have VideoLUT access.</a></h4>
    <h4><br>
      <a href="#PS1">Profiling Scanners and other input devices such as
        cameras<br>
      </a></h4>
    <h4>&nbsp;&nbsp;&nbsp; <a href="#PS2">Types of test charts</a></h4>
    <h4>&nbsp;&nbsp;&nbsp; <a href="#PS3">Taking readings from a
        scanner</a></h4>
    <h4>&nbsp;&nbsp;&nbsp; <a href="#PS4">Creating a scanner profile</a></h4>
    <h4><br>
      <a href="#PP1">Profiling Printers</a></h4>
    <h4> &nbsp;&nbsp;&nbsp; <a href="#PP2">Creating a print profile
        test chart</a></h4>
    <h4> &nbsp;&nbsp;&nbsp; <a href="Scenarios.html#PP2b">Printing a
        print profile test chart</a></h4>
    <h4> &nbsp;&nbsp;&nbsp; <a href="#PP3">Reading a print test chart
        using an instrument</a></h4>
    <h4> &nbsp;&nbsp;&nbsp; <a href="#PP4">Reading a print test chart
        using a scanner</a></h4>
    <h4> </h4>
    <h4>&nbsp;&nbsp;&nbsp; <a href="#PP5">Creating a printer profile<br>
      </a></h4>
    <h4>&nbsp;&nbsp;&nbsp; <a href="#PP6">Choosing a black generation
        curve</a></h4>
    <br>
    <h4><a href="Scenarios.html#PC1">Calibrating Printers</a></h4>
    <h4> &nbsp;&nbsp;&nbsp; <a href="Scenarios.html#PC2">Calibrated
        print workflows</a></h4>
    <h4> &nbsp;&nbsp;&nbsp; <a href="Scenarios.html#PC3">Creating a
        print calibration test chart</a></h4>
    <h4> </h4>
    <h4>&nbsp;&nbsp;&nbsp; <a href="Scenarios.html#PC4">Creating a
        printer calibration<br>
      </a></h4>
    <h4>&nbsp;&nbsp;&nbsp; <a href="Scenarios.html#PC5">Using a printer
        calibration</a></h4>
    <h4>&nbsp;&nbsp;&nbsp; <a href="#PC6">How profile ink limits are
        handled when calibration is being used<br>
      </a></h4>
    <h4> <a href="#LP1">Linking Profiles</a></h4>
    <p>&nbsp;&nbsp;&nbsp; <b><a href="#LP2">Image dependent gamut
          mapping using device links</a></b><br>
    </p>
    <p>&nbsp;&nbsp;&nbsp; <b><a href="#LP2">Soft Proofing Link</a></b><br>
    </p>
    <h4> <a href="#TR1">Transforming colorspaces of raster files</a></h4>
    <h4></h4>
    <h4> <a href="#TV1">Creating Video Calibration 3DLuts</a></h4>
    <h4><a href="Scenarios.html#TV2">Verifying Video Calibration 3DLuts</a></h4>
    <br>
    <hr style="width: 100%; height: 2px;"><br>
    <h3><a name="PM1"></a>Profiling Displays</h3>
    Argyll supports adjusting, calibrating and profiling of displays
    using one of a number of instruments - see <a
      href="instruments.html">instruments</a> for a current list.&nbsp;
    Adjustment and calibration are prior steps to profiling, in which
    the display is adjusted using it's screen controls,&nbsp; and then
    per channel lookup tables are created to make it meet a well behaved
    response of the desired type. The&nbsp; process following that of
    creating a display profile is then similar to that of all other
    output devices :- first a set of device colorspace test values needs
    to be created to exercise the display, then these values need to be
    displayed, while taking measurements of the resulting colors using
    the instrument. Finally, the device value/measured color values need
    to be converted into an ICC profile.<br>
    <br>
    <h3><a name="PM1a"></a>Checking you can access your display<br>
    </h3>
    You might first want to check that you are accessing and can
    calibrate your display. You can do this using the <a
      href="dispwin.html">dispwin</a><span style="font-weight: bold;"></span>
    tool<span style="font-weight: bold;">.</span> If you just run <span
      style="font-weight: bold;">dispwin</span> it will create a test
    window and run through a series of test colors before checking that
    the VideoLUT can be accessed by the display. If you invoke the usage
    for <span style="font-weight: bold;">dispwin</span> (by giving it
    an unrecognized option, e.g. <span style="font-weight: bold;">-?</span>)
    then it will show a list of available displays next to the <span
      style="font-weight: bold;"><span style="font-weight: bold;">-d</span></span>
    flag. Make sure that you are accessing the display you intend to
    calibrate and profile, and that the VideoLUT is effective (the <span
      style="font-weight: bold;">-r</span> flag can be used to just run
    the VideoLUT test). You can also try clearing the VideoLUTs using
    the <span style="font-weight: bold;">-c</span> flag, and loading a
    deliberately strange looking calibration <span style="font-weight:
      bold;">strange.cal</span> that is provided in the Argyll <span
      style="font-weight: bold;">ref</span> directory.<br>
    <br>
    Note that calibrating and/or profiling <span style="font-weight:
      bold;">remote</span> displays is possible using X11 or a web
    browser (see <span style="font-weight: bold;">-d</span> option of
    dispcal and dispread), or by using some external program to send
    test colors to a display (see <span style="font-weight: bold;">-C</span>
    and <span style="font-weight: bold;">-M</span> options of dispcal
    and dispread), but you may want to refer to <a href="#PM7">Calibrating




















































      and profiling a display that doesn't have VideoLUT access</a>.<br>
    <br>
    <h3><a name="PM1b"></a>Adjusting and Calibrating Displays</h3>
    Please read <a href="calvschar.html">What's the difference between
      Calibration and Characterization ?</a> if you are unclear as to
    the difference .<br>
    <br>
    The first step is to decide what the target should be for adjustment
    and calibration. This boils down to three things: The desired
    brightness, the desired white point, and the desired response curve.
    The native brightness and white points of a display may be different
    to the desired characteristics for some purposes. For instance, for
    graphic arts use, it might be desirable to run with a warmer white
    point of about 5000 degrees Kelvin, rather than the default display
    white point of 6500 to 9000 Kelvin. Some LCD displays are too bright
    to compare to printed material under available lighting, so it might
    be desirable to reduce the maximum brightness.<br>
    <br>
    You can run <a href="dispcal.html#r">dispcal -r</a> to check on how
    your display is currently set up. (you may have to run this as <span
      style="text-decoration: underline; color: rgb(204, 51, 204);">dispcal
-yl

























































      -r</span> for an LCD display, or <span style="text-decoration:
      underline; color: rgb(204, 51, 204);">dispcal -yc -r</span> for a
    CRT display with most of the colorimeter instruments. If so, this
    will apply to all of the following examples.)<br>
    <br>
    Once this is done, <a href="dispcal.html">dispcal</a> can be run to
    guide you through the display adjustments, and then calibrate it. By
    default, the brightness and white point will be kept the same as the
    devices natural brightness and white point. The default response
    curve is a gamma of 2.4, except for Apple OS X systems prior to 10.6
    where a gamma of 1.8 is the default. 2.4 is close to that of&nbsp;
    many monitors, and close to that of the sRGB colorspace. <br>
    <br>
    A typical calibration that leaves the brightness and white point
    alone, might be:<br>
    <br>
    <a href="dispcal.html">dispcal</a> -v TargetA<br>
    <br>
    which will result in a "TargetA.cal" calibration file, that can then
    be used during the profiling stage.<br>
    <br>
    If the absolutely native response of the display is desired during
    profiling, then calibration should be skipped, and the linear.cal
    file from the "ref" directory used instead as the argument to the -k
    flag of <span style="font-weight: bold;">dispread</span>.<br>
    <br>
    <b>Dispcal</b> will display a test window in the middle of the
    screen, and issue a series of instructions about placing the
    instrument on the display. You may need to make sure that the
    display cursor is not in the test window, and it may also be
    necessary to disable any screensaver and powersavers before starting
    the process, although both <span style="font-weight: bold;">dispcal</span>
    and <span style="font-weight: bold;">dispread</span> will attempt
    to do this for you. It's also highly desirable on CRT's, to clear
    your screen of any white or bright background images or windows
    (running your shell window with white text on a black background
    helps a lot here.), or at least keep any bright areas away from the
    test window, and be careful not to change anything on the display
    while the readings are taken. Lots of bright images or windows can
    affect the ability to measure the black point accurately, and
    changing images on the display can cause inconsistency in the
    readings,&nbsp; and leading to poor results.<span
      style="font-weight: bold;"></span> LCD displays seem to be less
    influenced by what else is on the screen.<br>
    <br>
    If <span style="font-weight: bold;">dispcal</span> is run without
    arguments, it will provide a usage screen. The <span
      style="font-weight: bold;">-c</span> parameter allows selecting a
    communication port for an instrument, or selecting the instrument
    you want to use,&nbsp; and the <a href="dispcal.html#d"><span
        style="font-weight: bold;">-d</span></a> option allows selecting
    a target display on a multi-display system. On some multi-monitor
    systems, it may not be possible to independently calibrate and
    profile each display if they appear as one single screen to the
    operating system, or if it is not possible to set separate video
    lookup tables for each display. You can change the position and size
    of the test window using the <a href="dispcal.html#P"><span
        style="font-weight: bold;">-P</span></a> parameter. You can
    determine how best to arrange the test window, as well as whether
    each display has separate video lookup capability, by experimenting
    with the <a href="dispwin.html">dispwin</a> tool. <br>
    <br>
    For a more detailed discussion on interactively adjusting the
    display controls using <span style="font-weight: bold;">dispcal</span>,
    see <a href="dispcal.html#Adjustment">dispcal-adjustment</a>. Once
    you have adjusted and calibrated your display, you can move on to
    the next step.<br>
    <br>
    When you have calibrated and profiled your display, you can keep it
    calibrated using the <a href="dispcal.html#u">dispcal -u</a>
    option.<br>
    <br>
    <h4><a name="PM1c"></a>Adjusting, calibrating and profiling in one
      step.</h4>
    If a simple matrix/shaper display profile is all that is desired, <span
      style="font-weight: bold;">dispcal</span> can be used to do this,
    permitting display adjustment, calibration and profiling all in one
    operation. This is done by using the <span style="font-weight:
      bold;"><span style="font-weight: bold;">dispcal </span>-o</span>
    flag:<br>
    <br>
    <a href="dispcal.html">dispcal</a> <a href="dispcal.html#v">-v</a>
    <a href="dispcal.html#o">-o</a> <a href="dispcal.html#p1">TargetA</a><br>
    <br>
    This will create both a TargetA.cal file, but also a TargetA.icm
    file. See <a href="dispcal.html#o">-o</a> and <a
      href="dispcal.html#O">-O</a> for other variations.<br>
    <br>
    For more flexibility in creating a display profile, the separate
    steps of creating characterization test values using <span
      style="font-weight: bold;">targen</span>, reading them from the
    display using <span style="font-weight: bold;">dispread</span>, and
    then creating a profile using <span style="font-weight: bold;">colprof</span>
    are used. The following steps illustrate this:<br>
    <h4><a name="PM2"></a>Profiling in several steps: Creating display
      test values</h4>
    If the <span style="font-weight: bold;">dispcal</span> has not been
    used to create a display profile at the same time as adjustment and
    calibration, then it can be used to create a suitable set of
    calibration curves as the first step, or the calibration step can be
    omitted, and the display cansimply be profiled.<br>
    <br>
    The first step in profiling any output device, is to create a set of
    device colorspace test values. The important parameters needed are:
    <br>
    <ul>
      <li>What colorspace does the device use ?</li>
      <li>How many test patches do I want to use ?</li>
      <li>What information do I already have about how the device
        behaves ?</li>
    </ul>
    For a display device, &nbsp;the colorspace will be RGB. The number
    of test patches will depend somewhat on what quality profile you
    want to make, what type of profile you want to make, and how long
    you are prepared to wait when testing the display.<br>
    At a minimum, a few hundred values are needed. A matrix/shaper type
    of profile can get by with fewer test values, while a LUT based
    profile will give better results if more test values are used. A
    typical number might be 200-600 or so values, while 1000-2000 is not
    an unreasonable number for a high quality characterization of a
    display.<br>
    <br>
    To assist the choice of test patch values, it can help to have a
    rough idea of how the device behaves. This could be in the form of
    an ICC profile of a similar device, or a lower quality, or previous
    profile for that particular device. If one were going to make a very
    high quality LUT based profile, then it might be worthwhile to make
    up a smaller, preliminary shaper/matrix profile using a few hundred
    test points, before embarking on testing the device with several
    thousand.<br>
    <br>
    Lets say that we ultimately want to make a profile for the device
    "DisplayA", the simplest approach is to make a set of test values
    that is independent of the characteristics of the particular device:<br>
    <br>
    <a href="targen.html">targen</a> <a href="targen.html#v">-v</a>
    &nbsp;<a href="targen.html#d">-d3</a> <a href="targen.html#f">-f500</a>
    <a href="targen.html#p1">DisplayA</a><br>
    <br>
    If there is a preliminary or previous profile called "OldDisplay"
    available, and we want to try creating a "pre-conditioned" set of
    test values that will more efficiently sample the device response,
    then the following would achieve this:<br>
    <u><br>
    </u><a href="targen.html"> targen</a> <a href="targen.html#v">-v</a>
    &nbsp;<a href="targen.html#d">-d3</a> <a href="targen.html#f">-f500</a>
    <a href="targen.html#c">-cOldDisplay.icm</a> <a
      href="targen.html#p1">DisplayA</a><br>
    <br>
    The output of <b>targen</b> will be the file DisplayA.ti1,
    containing the device space test values, as well as expected CIE
    values used for chart recognition purposes.<br>
    <br>
    <h4><a name="PM3"></a>Profiling in several steps: Taking readings
      from a display</h4>
    First it is necessary to connect your measurement instrument to your
    computer, and check which communication port it is connected to. In
    the following example, it is assumed that the instrument is
    connected to the default port 1, which is either the first USB
    instrument found, or serial port found. Invoking dispread so as to
    display the usage information (by using a flag -? or --) will list
    the identified serial and USB ports, and their labels.<br>
    <br>
    <a href="dispread.html">dispread</a> <a href="dispread.html#v">-v</a>
    <a href="dispread.html#p1">DisplayA</a><br>
    <br>
    If we created a calibration for the display using <a
      href="dispcal.html">dispcal</a>, then we will want to use this
    when we take the display readings (e.g. TargetA.cal from the
    calibration example)..<br>
    <br>
    <a href="dispread.html">dispread</a> <a href="dispread.html#v">-v</a>
    <a href="dispread.html#k">-k TargetA.cal</a> <a
      href="dispread.html#p1">DisplayA</a><br>
    <br>
    <b>dispread</b> will display a test window in the middle of the
    screen, and issue a series of instructions about placing the
    instrument on the display. You may need to make sure that the
    display cursor is not in the test window, and it may also be
    necessary to disable any screensaver before starting the process.
    Exactly the same facilities are provided to select alternate
    displays using the <span style="font-weight: bold;">-d</span>
    parameter, and an alternate location and size for the test window
    using the <span style="font-weight: bold;">-P</span> parameter as
    with <span style="font-weight: bold;">dispcal</span>.<br>
    <h4><a name="PM4"></a>Profiling in several steps: Creating a display
      profile</h4>
    There are two basic choices of profile type for a display, a
    shaper/matrix profile, or a LUT based profile. They have different
    tradeoffs. A shaper/matrix profile will work well on a well behaved
    display, that is one that behaves in an additive color manner, will
    give very smooth looking results, and needs fewer test points to
    create. A LUT based profile on the other hand, will model any
    display behaviour more accurately, and can accommodate gamut mapping
    and different intent tables. Often it can show some unevenness and
    contouring in the results though.<br>
    <br>
    To create a matrix/shaper profile, the following suffices:<br>
    <br>
    <a href="colprof.html">colprof</a> <a href="colprof.html#v">-v</a>
    <a href="colprof.html#E">-D"Display A"</a> <a href="colprof.html#q">-qm</a>
    <a href="colprof.html#a">-as</a> <a href="colprof.html#p1">DisplayA</a><br>
    <br>
    For a LUT based profile, where gamut mapping is desired, then a
    source profile will need to be provided to define the source gamut.
    For instance, if the display profile was likely to be linked to a
    CMYK printing source profile, say "swop.icm" or "fogra39l.icm", then
    the following would suffice:<br>
    <br>
    <a href="colprof.html">colprof</a> <a href="colprof.html#v">-v</a>
    <a href="colprof.html#E">-D"Display A"</a> <a href="colprof.html#q">-qm</a>
    <a href="colprof.html#S">-S</a><a href="colprof.html#S">
      fogra39l.icm</a> <a href="colprof.html#c">-cpp</a> <a
      href="colprof.html#d">-dmt</a> <a href="colprof.html#p1">DisplayA</a><br>
    <br>
    Make sure you check the delta E report at the end of the profile
    creation, to see if the sample data and profile is behaving
    reasonably.<br>
    If a calibration file was used with <a href="dispread.html">dispread</a>,
    then it will be converted to a vcgt tag in the profile, so that the
    operating system or other system color tools load the lookup curves
    into the display hardware, when the profile is used.<br>
    <h4><a name="PM5"></a>Installing a display profile</h4>
    <a href="dispwin.html">dispwin</a> provides a convenient way of
    installing a profile as the default system profile for the chosen
    display:<br>
    <br>
    <a href="dispwin.html">dispwin</a> <a href="dispwin.html#I">-I</a>
    <a href="dispwin.html#p1">DisplayA.icm</a><br>
    <br>
    This also sets the display to the calibration contained in the
    profile. If you want to try out a calibration before installing the
    profile, using dispwin without the <span style="font-weight: bold;">-I</span>
    option will load a calibration (ICC profile or .cal file) into the
    current display.<br>
    <br>
    Some systems will automatically set the display to the calibration
    contained in the installed profile (ie. OS X), while on other
    systems (ie. MSWindows and Linux/X11) it is necessary to use some
    tool to do this. On MSWindows XP you could install the
    optional&nbsp; <span style="font-weight: bold;">Microsoft&nbsp;Color&nbsp;Control&nbsp;Panel&nbsp;Applet&nbsp;for&nbsp;Windows&nbsp;XP</span>
    available for download from Microsoft to do this, but&nbsp;<span
      style="font-weight: bold;">NOTE</span> however that it seems to
    have a <span style="font-weight: bold;">bug</span>, in that it
    sometimes associates the profiles with the <span
      style="font-weight: bold;">wrong monitor</span> entry. Other
    display calibration tools will often install a similar tool, so
    beware of there being multiple, competing programs. [ Commonly these
    will be in your Start-&gt;Programs-&gt;Startup folder. ]<br>
    On Microsoft Vista, you need to use dispwin -L or some other tool to
    load the installed profiles calibration at startup.<br>
    <br>
    To use dispwin to load the installed profiles calibration to the
    display, use<br>
    <br>
    <a href="dispwin.html">dispwin</a> <a href="dispwin.html#L">-L</a><br>
    <br>
    As per usual, you can select the appropriate display using the <a
      href="dispwin.html#d">-d</a> flag.<br>
    <br>
    This can be automated on MSWindows and X11/Linux by adding this
    command to an appropriate startup script.<br>
    More system specific details, including how to create such startup
    scripts are <a href="dispprofloc.html">here</a>. <br>
    <br>
    If you are using Microsoft <span style="font-weight: bold;">Vista</span>,
    there is a known <span style="font-weight: bold;">bug</span> in
    Vista that resets the calibration every time a fade-in effect is
    executed, which happens if you lock and unlock the computer, resume
    from sleep or hibernate, or User Access Control is activated. Using
    <a href="dispwin.html">dispwin</a> <a href="dispwin.html#L">-L</a>
    may not restore the calibration, because Vista filters out setting
    (what it thinks) is a calibration that is already loaded. Use <a
      href="dispwin.html">dispwin</a> <a href="dispwin.html#c">-c</a> <a
      href="dispwin.html#L">-L</a><span style="font-family: monospace;"></span>
    as a workaround, as this will first clear the calibration, then
    re-load the current calibration.<br>
    <br>
    On X11/Linux systems, you could try adding <a href="dispwin.html">dispwin</a>
    <a href="dispwin.html#L">-L</a> to your <span style="font-weight:
      bold;">~/.config/autostart</span> file, so that your window
    manager automatically sets calibration when it starts. If you are
    running XRandR 1.2, you might consider running the experimental <a
      href="dispwin.html#D">dispwin -E</a> in the background, as in its
    "daemon" mode it will update the profile and calibration in response
    to any changes in the the connected display.<br>
    <br>
    <h4><a name="PM6"></a>Expert tips when measuring displays:<br>
    </h4>
    Sometimes it can be difficult to get good quality, consistent and
    visually relevant readings from displays, due to various practical
    considerations with regard to instruments and the displays
    themselves. Argyll's tools have some extra options that may assist
    in overcoming these problems.<br>
    <br>
    If you are using an Eye-One Pro or ColorMunki spectrometer, then you
    may wish to use the <a href="dispcal.html#H">high resolution
      spectral mode</a> (<span style="font-weight: bold;">-H</span>).
    This may be better at capturing the often narrow wavelength peaks
    that are typical of display primary colors.<br>
    <br>
    All instruments depend on silicon sensors, and such sensors generate
    a temperature dependant level of noise ("dark noise") that is
    factored out of the measurements by a dark or black instrument
    calibration. The spectrometers in particular need this calibration
    before commencing each set of measurements. Often an instrument will
    warm up as it sits on a display, and this warming up can cause the
    dark noise to increase, leading to inaccuracies in dark patch
    measurements. The longer the measurement takes, the worse this
    problem is likely to be. One way of addressing this is to
    "acclimatise" the instrument before commencing measurements by
    placing it on the screen in a powered up state, and leaving it for
    some time. (Some people leave it for up to an hour to acclimatise.).
    Another approach is to try and <a href="dispcal.html#I">compensate
      for dark calibration changes</a> (<span style="font-weight: bold;">-Ib</span>)
    by doing on the fly calibrations during the measurements, based on
    the assumption that the black level of the display itself won't
    change significantly. <br>
    <br>
    Some displays take a long time to settle down and stabilise. The is
    often the case with LCD (Liquid Crystal) displays that use
    fluorescent back lights, and these sorts of displays can change in
    brightness significantly with changes in temperature. One way of
    addressing this is to make sure that the display is given adequate
    time to warm up before measurements. Another approach is to try and
    <a href="dispcal.html#I">compensate for display white level</a>&nbsp;

























































    (<span style="font-weight: bold;">-Iw</span>) changes by doing on
    the fly calibrations during the measurements. Instrument black level
    drift and display white level drift can be combined (<span
      style="font-weight: bold;">-Ibw</span>).<br>
    <br>
    Colorimeter instruments make use of physical color filters that
    approximate the standard observer spectral sensitivity curves.
    Because these filters are not perfectly accurate, the manufacturer
    calibrates the instrument for typical displays, which is why you
    have to make a selection between CRT (Cathode Ray Tube) and LCD
    (Liquid Crystal Display) modes. If you are measuring a display that
    has primary colorants that differ significantly from those typical
    displays,&nbsp; (ie. you have a Wide Gamut Display), then you may
    get disappointing results with a Colorimeter. One way of addressing
    this problem is to use a <a href="File_Formats.html#.ccmx">Colorimeter
























































      Correction Matrix</a>. These are specific to a particular
    Colorimeter and Display make and model combination, although a
    matrix for a different but similar type of display may give better
    results than none at all. A list of contributed <span
      style="font-weight: bold;">ccmx</span> files is <a
      href="ccmxs.html">here</a>.<br>
    <br>
    <h4><a name="PM7"></a>Calibrating and profiling a display that
      doesn't have VideoLUT access.</h4>
    <p>In some situation there is no access to a displays VideoLUT
      hardware, and this hardware is what is usually used to implement
      display calibration. This could be because the display is being
      accessed via a web server, or because the driver or windowing
      system doesn't support VideoLUT access.<br>
    </p>
    <p>There are two basic options in this situation:<br>
    </p>
    <p>&nbsp; 1) Don't attempt to calibrate, just profile the display.<br>
      &nbsp; 2) Calibrate, but incorporate the calibration in some other
      way in the workflow.<br>
    </p>
    <p>The first case requires nothing special - just skip calibration
      (see the previous section <a href="#PM7">Profiling in several
        steps: Creating display test values</a>).</p>
    <p> In the second case, there are three choices:<br>
    </p>
    <p>&nbsp;2a) Use dispcal to create a calibration and a quick profile
      that incorporates the calibration into the profile.<br>
      &nbsp;2b) Use dispcal to create the calibration, then dispread and
      colprof to create a profile, and then incorporate the calibration
      into the profile using applycal.<br>
      &nbsp;2c) Use dispcal to create the calibration, then dispread and
      colprof to create a profile, and then apply the calibration after
      the profile in a cctiff workflow.<br>
    </p>
    <p>The first case requires nothing special, use dispcal in a normal
      fashioned with the <span style="font-weight: bold;">-o</span>
      option to generate a quick profile.The profile created will <span
        style="text-decoration: underline;">not</span> contain a 'vcgt'
      tag, but instead will have the calibration curves incorporated
      into the profile itself. If calibration parameters are chosen that
      change the displays white point or brightness, then this will
      result in a slightly unusual profile that has a white point that
      does not correspond with device R=G=B=1.0. Some systems may not
      cope properly with this type of profile, and a general shift in
      white point through such a profile can create an odd looking
      display if it is applied to images but not to other elements on
      the display say as GUI decoration elements or other application
      windows.<br>
    </p>
    <p>In the second case, the calibration file created using dispcal
      should be provided to dispread using the <span
        style="font-weight: bold;">-K</span> flag:<br>
    </p>
    <p><a href="dispread.html">dispread</a> <a href="dispread.html#v">-v</a>
      <a href="dispread.html#K">-K TargetA.cal</a> <a
        href="dispread.html#p1">DisplayA</a></p>
    <p><span style="font-weight: bold;"></span>Create the profile as
      usual using colprof. but note that colprof will ignore the
      calibration, and that no 'vcgt' tag will be added to the profile.<br>
      You can then use <a href="applycal.html">applycal </a>to combine
      the calibration into the profile. Note that the resulting profile
      will be slightly unusual, since the profile is not made completely
      consistent with the effects of the calibration, and the device
      R=G=B=1.0 probably not longer corresponds with the PCS white or
      the white point.<br>
    </p>
    In the third case, the same procedure as above is used to create a
    profile, but the calibration is applied in a raster transformation
    workflow explicitly, e.g.:<br>
    <br>
    &nbsp;&nbsp;&nbsp; <a href="cctiff.html">cctiff</a> <a
      href="cctiff.html#p1">SourceProfile.icm</a> <a
      href="cctiff.html#p1">DisplayA.icm</a> <a href="cctiff.html#p2">DisplayA.cal</a>
    <a href="cctiff.html#p3">infile.tif</a> <a href="cctiff.html#p4">outfile.tif</a><br>
    or<br>
    &nbsp;&nbsp;&nbsp; <a href="cctiff.html">cctiff</a> <a
      href="cctiff.html#p1">SourceProfile.icm</a> <a
      href="cctiff.html#p1">DisplayA.icm</a> <a href="cctiff.html#p2">DisplayA.cal</a>
    <a href="cctiff.html#p3">infile.jpg</a> <a href="cctiff.html#p4">outfile.jpg</a><br>
    <span style="font-weight: bold;"></span><br>
    <hr size="2" width="100%">
    <h3><a name="PS1"></a>Profiling Scanners and other input devices
      such as cameras<br>
    </h3>
    Because a scanner or camera is an input device, it is necessary to
    go about profiling it in quite a different way to an output device.
    To profile it, a test chart is needed to exercise the input device
    response, to which the CIE values for each test patch is known.
    Generally standard reflection or transparency test charts are used
    for this purpose.<br>
    <h4><a name="PS2"></a>Types of test charts</h4>
    The most common and popular test chart for scanner profiling is the
    IT8.7/2 chart. This is a standard format chart generally reproduced
    on photographic film, containing about 264 test patches.<br>
    An accessible and affordable source of such targets is Wolf Faust a
    <a href="http://www.targets.coloraid.de/">www.coloraid.de</a>.<br>
    Another source is LaserSoft <a
      href="http://www.silverfast.com/show/it8/en.html">www.silverfast.com.</a><br>
    The Kodak Q-60 Color Input Target is also a typical example:<br>
    <br>
    <img src="Q60.jpg" alt="Kodak Q60 chart image" height="141"
      width="200"> <br>
    <br>
    A very simple chart that is widely available is the Macbeth
    ColorChecker chart, although it contains only 24 patches and
    therefore is probably not ideal for creating profiles:<br>
    <img alt="ColorChecker 24 patch" src="colorchecker.jpg"
      style="width: 112px; height: 78px;"><br>
    <br>
    Other popular charts are the X-Rite/GretagMacbeth ColorChecker DC
    and <a href="http://www.xrite.com/product_overview.aspx?ID=938">ColorChecker

























































      SG</a> charts:<br>
    <br>
    <img src="DC.jpg" alt="GretagMacbeth ColorChecker DC chart"
      height="122" width="200"> <img alt="ColorChecker SG" src="SG.jpg"
      style="width: 174px; height: 122px;"><br>
    <br>
    The GretagMacbeth Eye-One Pro Scan Target 1.4 can also be used:<br>
    <br>
    <img alt="Eye-One Scan Target 1.4" src="i1scan14.jpg" style="border:
      2px solid ; width: 200px; height: 140px;"><br>
    <br>
    Also supported is the <a href="http://www.hutchcolor.com/hct.htm">HutchColor

























































      HCT</a> :<br>
    <br>
    <img alt="HutchColor HCT" src="HCT.jpg" style="width: 182px; height:
      140px;"><br>
    <br>
    <br>
    and <a href="http://www.cmp-color.fr/DT3.html">Christophe
      Métairie's Digital TargeT 003</a> and <a
      href="http://www.cmp-color.fr/digital%20target.html">Christophe
      Métairie's Digital Target - 4</a> :<br>
    <br>
    <img alt="CMP_DT_003" src="CMP_DT_003.jpg" style="width: 186px;
      height: 141px;">&nbsp; <img style="width: 203px; height: 140px;"
      alt="CMP_Digital_Target-4" src="CMP_Digital_Target-4.jpg"
      height="140" width="203"><br>
    <br>
    and the <a href="http://www.silverfast.com/show/dc-targets/en.html">LaserSoft

























































      Imaging DCPro Target</a>:<br>
    <br>
    <img style="width: 153px; height: 122px;" alt="LaserSoft DCPro
      Target" src="LSDC.jpg"><br>
    <br>
    The Datacolor <a
      href="http://spyder.datacolor.com/product-cb-spydercheckr.php">SpyderCheckr</a>:<br>
    <br>
    <img style=" width: 146px; height: 109px;" alt="Datacolor
      SpyderCheckr" src="SpyderChecker.jpg"><br>
    <br>
    One of the QPcard's:<br>
    <a
      href="http://www.qpcard.com/en_b2c/color-reference-cards/qpcard201.html">QPcard



















































      201</a>:&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; <a
href="http://www.qpcard.com/en_b2c/color-reference-cards/instant-camera-raw-profiling-with-qpcard-202.html">QPcard



















































      202</a>:<br>
    <br>
    <img style=" width: 41px; height: 141px;" alt="QPCard201"
      src="QPcard201.jpg">&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;
    &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; <img
      style=" width: 97px; height: 141px;" alt="QPcard202"
      src="QPcard202.jpg"><br>
    <br>
    <h4><a name="PS3"></a>Taking readings from a scanner or camera<br>
    </h4>
    The test chart you are using needs to be placed on the scanner, and
    the scanner needs to be configured to a suitable state, and restored
    to that same state when used subsequently with the resulting
    profile. For a camera, the chart needs to be lit in a controlled and
    even manner using the light source that will be used for subsequent
    photographs, and should be shot so as to minimise any geometric
    distortion, although the <a href="scanin.html#p">scanin -p</a> flag
    may be used to compensate for some degree of distortion. As with any
    color profiling task, it is important to setup a known and
    repeatable image processing flow, to ensure that the resulting
    profile will be usable.<br>
    <br>
    The chart should be captured and saved to a TIFF format file. I will
    assume the resulting file is called scanner.tif. The raster file
    need only be roughly cropped so as to contain the test chart
    (including the charts edges).<br>
    <br>
    The second step is to extract the RGB values from the scanner.tif
    file, and match then to the reference CIE values. To locate the
    patch values in the scan, the <b>scanin</b> tool needs to be given
    a template <a href="File_Formats.html#.cht">.cht</a> file that
    describes the features of the chart, and how the test patches are
    labeled. Also needed is a file containing the CIE values for each of
    the patches in the chart, which is typically supplied with the
    chart, available from the manufacturers web site, or has been
    measured using a spectrometer.<br>
    <br>
    <div style="margin-left: 40px;">For an IT8.7/2 chart, this is the <span
        style="font-weight: bold;">ref/</span><b>it8.cht</b> file
      supplied with Argyll, and&nbsp; the manufacturer will will supply
      an individual or batch average file along with the chart
      containing this information, or downloadable from their web site.
      For instance, Kodak Q60 target reference files are <a
        href="ftp://ftp.kodak.com/gastds/Q60DATA/">here</a>.<br>
      NOTE that the reference file for the IT8.7/2 chart supplied with <span
        style="font-weight: bold;">Monaco&nbsp;EZcolor</span> can be
      obtained by unzipping the .mrf file. (You may have to make a copy
      of the file with a .zip extension to do this.)<br>
      <br>
      For the ColorChecker 24 patch chart, the <span
        style="font-weight: bold;">ref/ColorChecker.cht</span> file
      should be used, and there is also a <span style="font-weight:
        bold;">ref/ColorChecker.cie</span> file provided that is based
      on the manufacturers reference values for the chart. You can also
      create your own reference file using an instrument and chartread,
      making use of the chart reference file <span style="font-weight:
        bold;">ref/ColorChecker.ti2</span>:<br>
      &nbsp;&nbsp; <a href="chartread.html">chartread</a> -n
      ColorChecker.ti2<br>
      Note that due to the small number of patches, a profile created
      from such a chart is not likely to be very detailed.<br>
      <br>
      For the ColorChecker DC chart, the <span style="font-weight:
        bold;">ref/ColorCheckerDC.cht</span> file should be used, and
      there will be a ColorCheckerDC reference file supplied by
      X-Rite/GretagMacbeth with the chart.<br>
      <br>
      The ColorChecker SG is relatively expensive, but is preferred by
      many people because (like the ColorChecker and ColorCheckerDC) its
      colors are composed of multiple different pigments, giving it
      reflective spectra that are more representative of the real world,
      unlike many other charts that are created out of combination of 3
      or 4 colorants.<br>
      A limited CIE reference file is available from X-Rite <a
href="http://www.xrite.com/documents/apps/public/digital_colorchecker_sg_l_a_b.txt">here</a>,
      but it is not in the usual CGATS format. To convert it to a CIE
      reference file useful for <span style="font-weight: bold;">scanin</span>,
      you will need to edit the X-Rite file using a <span
        style="text-decoration: underline;">plain text</span> editor,
      first deleting everything before the line starting with "A1" and
      everything after "N10", then prepending <a href="SG_header.txt">this
























































        header</a>, and appending <a href="SG_footer.txt">this footer</a>,
      making sure there are no blank lines inserted in the process.
      There are reports that X-Rite have experimented with different ink
      formulations for certain patches, so the above reference may not
      be as accurate as desired, and it is preferable to measure your
      own chart using a spectrometer, if you have the capability.<br>
      If you do happen to have access to a more comprehensive instrument
      measurement of the ColorChecker SG, or you have measured it
      yourself using a color instrument,<br>
      then you <span style="text-decoration: underline;">may</span>
      need to convert the reference information from spectral <span
        style="font-weight: bold;">ColorCheckerSG.txt</span> file to CIE
      value <span style="font-weight: bold;">ColorCheckerSG.cie</span>
      reference file, follow the following steps:<br>
      &nbsp;&nbsp;&nbsp;&nbsp; <a href="txt2ti3.html">txt2ti3</a>
      ColorCheckerSG.txt ColorCheckerSG<br>
      &nbsp;&nbsp;&nbsp;&nbsp; <a href="spec2cie.html">spec2cie</a>
      ColorCheckerSG.ti3 ColorCheckerSG.cie<br>
      <br>
      For the Eye-One Pro Scan Target 1.4 chart, the <span
        style="font-weight: bold;"><span style="font-weight: bold;">ref/</span>i1_RGB_Scan_1.4.cht</span>
      file should be used, and as there is no reference file
      accompanying this chart, the chart needs to be read with an
      instrument (usually the Eye-One Pro). This can be done using
      chartread,&nbsp; making use of the chart reference file <span
        style="font-weight: bold;">ref/i1_RGB_Scan_1.4.ti2</span>:<br>
      &nbsp;&nbsp;&nbsp; <a href="chartread.html">chartread</a> -n
      i1_RGB_Scan_1.4<br>
      and then rename the resulting <span style="font-weight: bold;">i1_RGB_Scan_1.4.ti3</span>
      file to <span style="font-weight: bold;">i1_RGB_Scan_1.4.cie</span><br>
      <span style="font-weight: bold;"></span><br>
      For the HutchColor HCT chart, the <span style="font-weight:
        bold;"><span style="font-weight: bold;">ref/</span>Hutchcolor.cht</span>
      file should be used, and the reference <span style="font-weight:
        bold;">.txt</span> file downloaded from the HutchColor website.<br>
      <br>
      For the Christophe Métairie's Digital TargeT 003 chart with 285
      patches, the <span style="font-weight: bold;"><span
          style="font-weight: bold;">ref/</span>CMP_DT_003.cht</span>
      file should be used, and the cie reference <span
        style="font-weight: bold;"></span>files come with the chart.<br>
      <br>
      For the Christophe Métairie's Digital Target-4 chart with 570
      patches, the <span style="font-weight: bold;">ref/CMP_Digital_Target-4.cht</span>
      file should be used, and the cie reference <span
        style="font-weight: bold;"></span>files come with the chart.<br>
      <br>
      For the LaserSoft DCPro chart, the <span style="font-weight:
        bold;">ref/LaserSoftDCPro.cht</span> file should be used, and
      reference <span style="font-weight: bold;">.txt</span> file
      downloaded from the <a
        href="http://www.silverfast.com/it8calibration/">Silverfast
        website</a>.<br>
      <br>
      For the Datacolor SpyderCheckr, the <span style="font-weight:
        bold;">ref/SpyderChecker.cht</span> file should be used, and a
      reference <span style="font-weight: bold;">ref/SpyderChecker.cie
      </span>file made from measuring a sample chart is also available.
      Alternately you could create your own reference file by
      transcribing the <a
        href="http://spyder.datacolor.com/images/photo_checkr_colordatainfo.jpg">values</a>
      on the Datacolor website. <br>
      <br>
      For the QPCard 201, the <span style="font-weight: bold;">ref/QPcard_201.cht</span>
      file should be used, and a reference <span style="font-weight:
        bold;">ref/QPcard_201.cie</span> file made from measuring a
      sample chart is also available. <br>
      <br>
      For the QPCard 202, the <span style="font-weight: bold;">ref/QPcard_202.cht</span>
      file should be used, and a reference <span style="font-weight:
        bold;">ref/QPcard_202.cie</span> file made from measuring a
      sample chart is also available. <br>
    </div>
    <br>
    For any other type of chart, a chart recognition template file will
    need to be created (this is beyond the scope of the current
    documentation, although see&nbsp; the <a href="cht_format.html">.cht_format
























































      documentation</a>).<br>
    <br>
    To create the scanner .ti3 file, run the <b>scanin</b> tool as
    follows (assuming an IT8 chart is being used):<br>
    <br>
    <a href="scanin.html"> scanin</a> -v scanner.tif It8.cht It8ref.txt<br>
    <br>
    "It8ref.txt" or "It8ref.cie" is assumed to be the name of the CIE
    reference file supplied by the chart manufacturer. The resulting
    file will be named "<b>scanner.ti3</b>".<br>
    <br>
    <span style="font-weight: bold;">scanin</span> will process 16 bit
    per component .tiff files, which (if the scanner is capable of
    creating such files),&nbsp; may improve the quality of the profile.
    <br>
    <br>
    If you have any doubts about the correctness of the chart
    recognition, or the subsequent profile's delta E report is unusual,
    then use the scanin diagnostic flags <a href="scanin.html#d">-dipn</a>
    and examine the <span style="font-weight: bold;">diag.tif</span>
    diagnostic file, to make sure that the patches are identified and
    aligned correctly. If you have problems getting good automatic
    alignment, then consider doing a manual alignment by locating the
    fiducial marks on your scan, and feeding them into scanin <a
      href="scanin.html#F">-F</a> parameters. The fiducial marks should
    be listed in a clockwise direction starting at the top left.<br>
    <h4><a name="PS4"></a>Creating a scanner or camera input profile</h4>
    Similar to a display profile, an input profile can be either a
    shaper/matrix or LUT based profile. Well behaved input devices will
    probably give the best results with a shaper/matrix profile, and
    this may also be the best choice if your test chart has a small or
    unevenly distributed set of test patchs (ie. the IT8.7.2). If a
    shaper/matrix profile is a poor fit, consider using a LUT type
    profile.<br>
    <br>
    When creating a LUT type profile, there is the choice of XYZ or
    L*a*b* PCS (Device independent, Profile Connection Space). Often for
    input devices, it is better to choose the XYZ PCS, as this may be a
    better fit given that input devices are usually close to being
    linearly additive in behaviour.<br>
    <br>
    If the purpose of the input profile is to use it as a substitute for
    a colorimeter, then the <b>-u</b> flag should be used to avoid
    clipping values above the white point. Unless the shaper/matrix type
    profile is a very good fit, it is probably advisable to use a LUT
    type profile in this situation.<br>
    <br>
    To create a matrix/shaper profile, the following suffices:<br>
    <br>
    <a href="colprof.html">colprof</a> <a href="colprof.html#v">-v</a>
    <a href="colprof.html#E">-D"Scanner</a> <a href="colprof.html#E">A"</a>
    <a href="colprof.html#q">-qm</a> <a href="colprof.html#a">-as</a> <a
      href="colprof.html#p1">scanner</a><br>
    <br>
    For an XYZ PCS LUT based profile then the following would be used:<br>
    <br>
    <a href="colprof.html">colprof</a> <a href="colprof.html#v">-v</a>
    <a href="colprof.html#E">-D"Scanner A"</a> <a href="colprof.html#q">-qm</a>
    <a href="colprof.html#a">-ax</a> <a href="colprof.html#p1">scanner</a><br>
    <br>
    For the purposes of a poor mans colorimeter, the following would
    generally be used:<br>
    <br>
    <a href="colprof.html">colprof</a> <a href="colprof.html#v">-v</a>
    <a href="colprof.html#E">-D"Scanner A"</a> <a href="colprof.html#q">-qm</a>
    <a href="colprof.html#a">-ax</a> <a href="colprof.html#u">-u</a> <a
      href="colprof.html#p1">scanner</a><br>
    <br>
    Make sure you check the delta E report at the end of the profile
    creation, to see if the sample data and profile is behaving
    reasonably. Depending on the type of device, and the consistency of
    the readings, average errors of 5 or less, and maximum errors of 15
    or less would normally be expected. If errors are grossly higher
    than this, then this is an indication that something is seriously
    wrong with the device measurement, or profile creation.<br>
    <br>
    If profiling a <span style="font-weight: bold;">camera</span> in <span
      style="font-weight: bold;">RAW</span> mode, then there may be some
    advantage in creating a pure matrix only profile, in which it is
    assumed that the camera response is completely linear. This may
    reduce extrapolation artefacts. If setting the white point will be
    done in some application, then it may also be an advantage to use
    the <span style="font-weight: bold;">-u</span> flag and avoid
    setting the white point to that of the profile chart:<br>
    <br>
    <a href="colprof.html">colprof</a> <a href="colprof.html#v">-v</a>
    <a href="colprof.html#E">-D"Camera"</a> <a href="colprof.html#q">-qm</a>
    <a href="colprof.html#a">-am</a> <a href="colprof.html#u">-u</a> <a
      href="colprof.html#p1">scanner</a><br>
    <br>
    <br>
    <hr size="2" width="100%">
    <h3><a name="PP1"></a>Profiling Printers<br>
    </h3>
    The overall process is to create a set of device measurement target
    values, print them out, measure them, and then create an ICC profile
    from the measurements. If the printer is an RGB based printer, then
    the process is only slightly more complicated than profiling a
    display. If the printer is CMYK based, then some additional
    parameters are required to set the total ink limit (TAC) and
    &nbsp;black generation curve.<br>
    <h4><a name="PP2"></a>Creating a print profile test chart</h4>
    The first step in profiling any output device, is to create a set of
    device colorspace test values. The important parameters needed are:<br>
    <ul>
      <li>What colorspace does the device use ?</li>
      <li>How many test patches do I want to use/what paper size do I
        want to use ?</li>
      <li>What instrument am I going to use to read the patches ?<br>
      </li>
      <li>If it is a CMYK device, what is the total ink limit ?<br>
      </li>
      <li>What information do I already have about how the device
        behaves ?</li>
    </ul>
    Most printers running through simple drivers will appear as if they
    are RGB devices. In fact there is no such thing as a real RGB
    printer, since printers use white media and the colorant must
    subtract from the light reflected on it to create color, but the
    printer itself turns the incoming RGB into the native print
    colorspace, so for this reason we will tell targen to use the "Print
    RGB" colorspace, so that it knows that it's really a subtractive
    media. Other drivers will drive a printer more directly, and will
    expect a CMYK profile. [Currently Argyll is not capable of creating
    an ICC profile for devices with more colorants than CMYK. When this
    capability is introduced, it will by creating an additional
    separation profile which then allows the printer to be treated as a
    CMY or CMYK printer.] One way of telling what sort of profile is
    expected for your device is to examine an existing profile for that
    device using <a href="http://www.argyllcms.com/doc/iccdump.html">iccdump</a>.<br>
    <br>
    The number of test patches will depend somewhat on what quality
    profile you want to make, how well behaved the printer is, as well
    as the effort needed to read the number of test values. Generally it
    is convenient to fill a certain paper size with the maximum number
    of test values that will fit.<br>
    <br>
    At a minimum, for an "RGB" device, a few hundred values are needed
    (400-1000). For high quality CMYK profiles, 1000-3000 is not an
    unreasonable number of patches.<br>
    <br>
    To assist the determination of test patch values, it can help to
    have a rough idea of how the device behaves, so that the device test
    point locations can be pre-conditioned. This could be in the form of
    an ICC profile of a similar device, or a lower quality, or previous
    profile for that particular device. If one were going to make a very
    high quality Lut based profile, then it might be worthwhile to make
    up a smaller, preliminary shaper/matrix profile using a few hundred
    test points, before embarking on testing the device with several
    thousand.<br>
    <br>
    The documentation for the <a
      href="http://www.argyllcms.com/doc/targen.html">targen</a> tool
    lists a <a href="http://www.argyllcms.com/doc/targen.html#Table">table</a>
    of paper sizes and number of &nbsp;patches for typical situations.<br>
    <br>
    For a CMYK device, a total ink limit usually needs to be specified.
    Sometimes a device will have a maximum total ink limit set by its
    manufacturer or operator, and some CMYK systems (such as chemical
    proofing systems) don't have any limit. Typical printing devices
    such as Xerographic printers, inkjet printers and printing presses
    will have a limit. The exact procedure for determining an ink limit
    is outside the scope of this document, but one way of going about
    this might be to generate some small (say a few hundred patches)
    with targen &amp; pritntarg with different total ink limits, and
    printing them out, making the ink limit as large as possible without
    striking problems that are caused by too much ink.<br>
    <br>
    Generally one wants to use the maximum possible amount of ink to
    maximize the gamut available on the device. For most CMYK devices,
    an ink limit between 200 and 400 is usual, but and ink limit of 250%
    or over is generally desirable for reasonably dense blacks and dark
    saturated colors. And ink limit of less than 200% will begin to
    compromise the fully saturated gamut, as secondary colors (ie
    combinations of any two primary colorants) will not be able to reach
    full strength.<br>
    <br>
    Once an ink limit is used in printing the characterization test
    chart for a device, it becomes a critical parameter in knowing what
    the characterized gamut of the device is. If after printing the test
    chart, a greater ink limit were to be used, the the software would
    effectively be extrapolating the device behaviour at total ink
    levels beyond that used in the test chart, leading to inaccuracies.<br>
    <br>
    Generally in Argyll, the ink limit is established when creating the
    test chart values, and then carried through the profile making
    process automatically. Once the profile has been made however, the
    ink limit is no longer recorded, and you, the user, will have to
    keep track of it if the ICC profile is used in any program than
    needs to know the usable gamut of the device.<br>
    <br>
    <br>
    Lets consider two devices in our examples, "PrinterA" which is an
    "RGB" device, and "PrinterB" which is CMYK, and has a target ink
    limit of 250%. <br>
    <br>
    The simplest approach is to make a set of test values that is
    independent of the characteristics of the particular device:<br>
    <br>
    <a href="targen.html">targen</a> <a href="targen.html#v">-v</a>
    &nbsp;<a href="targen.html#d">-d2</a> <a href="targen.html#f">-f1053</a>
    <a href="targen.html#p1">PrinterA</a><br>
    <br>
    <a href="targen.html">targen</a> <a href="targen.html#v">-v</a>
    &nbsp;<a href="targen.html#d">-d4</a> <a href="targen.html#l">-l260</a>
    <a href="targen.html#f">-f1053</a> <a href="targen.html#p1">PrinterB</a><br>
    <br>
    The number of patches chosen here happens to be right for an A4
    paper size being read using a Spectroscan instrument. See the <a
      href="targen.html#Table">table</a> in&nbsp; the <a
      href="targen.html">targen</a> documentation for some other
    suggested numbers.<br>
    <br>
    If there is a preliminary or previous profile called "OldPrinterA"
    available, and we want to try creating a "pre-conditioned" set of
    test values that will more efficiently sample the device response,
    then the following would achieve this:<u><br>
    </u><br>
    <a href="targen.html">targen</a> <a href="targen.html#v">-v</a>
    &nbsp;<a href="targen.html#d">-d2</a> <a href="targen.html#f">-f1053</a>
    <a href="targen.html#c">-c OldPrinterA</a>&nbsp;<a
      href="targen.html#p1">PrinterA</a><br>
    <br>
    <a href="targen.html">targen</a> <a href="targen.html#v">-v</a>
    &nbsp;<a href="targen.html#d">-d4</a> <a href="targen.html#l">-l260</a>
    <a href="targen.html#f">-f1053</a> <a href="targen.html#c">-c
      OldPrinterB</a> <a href="targen.html#p1">PrinterB</a><br>
    <a href="targen.html#p1"></a><br>
    <br>
    The output of <b>targen</b> will be the file PrinterA.ti1 and
    PrinterB.ti1 respectively, containing the device space test values,
    as well as expected CIE values used for chart recognition purposes.<br>
    <br>
    <h4><a name="PP2b"></a>Printing a print profile test chart<br>
      <br>
    </h4>
    The next step is turn the test values in to a PostScript or TIFF
    raster test file that can printed on the device. The basic
    information that needs to be supplied is the type of instrument that
    will be used to read the patches, as well as the paper size it is to
    be formatted for.<br>
    <br>
    For an X-Rite DTP41, the following would be typical:<br>
    <br>
    <a href="printtarg.html">printtarg</a> <a href="printtarg.html#v">-v</a>
    <a href="printtarg.html#i">-i41</a> <a href="printtarg.html#p">-pA4</a>
    <a href="printtarg.html#p1">PrinterA</a><br>
    &nbsp;<br>
    For a Gretag Eye-One Pro, the following would be typical:<br>
    <br>
    <a href="printtarg.html">printtarg</a> <a href="printtarg.html#v">-v</a>
    <a href="printtarg.html#i">-ii1</a> <a href="printtarg.html#p">-pA4</a>
    <a href="printtarg.html#p1">PrinterA</a><br>
    <br>
    For using with a scanner as a colorimeter, the Gretag Spectroscan
    layout is suitable, but the <a href="printtarg.html#s">-s</a> flag
    should be used so as to generate a layout suitable for scan
    recognition, as well as generating the scan recognition template
    files. (You probably want to use less patches with <span
      style="font-weight: bold;">targen</span>, when using the <span
      style="font-weight: bold;">printtarg -s</span> flag, e.g. 1026
    patches for an A4R page, etc.) The following would be typical:<br>
    <br>
    <a href="printtarg.html">printtarg</a> <a href="printtarg.html#v">-v</a>
    <a href="printtarg.html#s">-s</a> <a href="printtarg.html#i">-iSS</a>
    <a href="printtarg.html#p">-pA4R</a> <a href="printtarg.html#p1">PrinterA</a><br>
    <span style="font-weight: bold;"><br>
      printtarg</span> reads the PrinterA.ti1 file, creates a
    PrinterA.ti2 file containing the layout information as well as the
    device values and expected CIE values, as well as a PrinterA.ps file
    containing the test chart. If the <span style="font-weight: bold;">-s</span>
    flag is used, one or more PrinterA.cht files is created to allow the
    <a href="scanin.html">scanin</a> program to recognize the chart.<br>
    <br>
    To create TIFF raster files rather than PostScript, use the <a
      href="printtarg.html#t"><span style="font-weight: bold;">-t</span></a>
    flag.<br>
    <br>
    <span style="font-weight: bold;">GSview</span> is a good program to
    use to check what the PostScript file will look like, without
    actually printing it out. You could also use <span
      style="font-weight: bold;">Photoshop</span> or <span
      style="font-weight: bold;">ImageMagick</span> for this purpose.<br>
    <br>
    The last step is to print the chart out.<br>
    <br>
    Using a suitable PostScript or raster file printing program,
    downloader, print the chart. If you are not using a TIFF test chart,
    and you do not have a PostScript capable printer, then an
    interpreter like GhostScript or even Photoshop could be used to
    rasterize the file into something that can be printed. Note that it
    is important that the PostScript interpreter or TIFF printing
    application and printer configuration is setup for a device
    profiling run, and that any sort of color conversion of color
    correction be turned off so that the device values in the PostScript
    or TIFF file are sent directly to the device. If the device has a
    calibration system, then it would be usual to have setup and
    calibrated the device before starting the profiling run, and to
    apply calibration to the chart values. If Photoshop was to be used,
    then either the chart needs to be a single page, or separate .eps or
    .tiff files for each page should be used, so that they can be
    converted and printed one at a time (see the <a
      href="printtarg.html#e">-e</a> and <a href="printtarg.html#t">-t</a>
    flags).<br>
    <br>
    <h4><a name="PP3"></a>Reading a print test chart using an instrument</h4>
    Once the test chart has been printed, the color of the patches needs
    to be read using a suitable instrument.<br>
    <br>
    Several different instruments are currently supported, some that
    need to be used patch by patch, some read a strip at a time, and
    some read a sheet at a time. See <a href="instruments.html">instruments</a>
    for a current list.<br>
    <br>
    The instrument needs to be connected to your computer before running
    the <a href="chartread.html">chartread</a> command. Both serial
    port and USB connected Instruments are supported. A serial port to
    USB adapter might have to be used if your computer doesn't have any
    serial ports, and you have a serial interface connected instrument.<br>
    <br>
    If you run <a href="chartread.html">chartread</a> so as to print
    out its usage message (ie. by using a <span style="font-weight:
      bold;">-?</span> or <span style="font-weight: bold;">--</span>
    flags), then it will list any identified serial ports or USB
    connected instruments, and their corresponding number for the <a
      href="chartread.html#c">-c</a> option. By default, <a
      href="chartread.html">chartread</a> will try to connect to the
    first available USB instrument, or an instrument on the first serial
    port.<br>
    <br>
    The only arguments required is to specify the basename of the .ti2
    file. If a non-default serial port is to be used, then the <span
      style="font-weight: bold;">-c</span> option would also be
    specified.<br>
    <br>
    &nbsp;e.g. for a Spectroscan on the second port:<br>
    <br>
    <a href="chartread.html">chartread</a> <a href="chartread.html#c">-c2</a>
    <a href="chartread.html#p1">PrinterA</a><br>
    <br>
    For a DTP41 to the default serial port:<br>
    <br>
    <a href="chartread.html">chartread</a><a href="chartread.html#i"></a>
    <a href="chartread.html#p1">PrinterA</a><br>
    <br>
    <span style="font-weight: bold;">chartread</span> will interactively
    prompt you through the process of reading each sheet or strip. See <a
      href="chartread.html">chartread</a> for more details on the
    responses for each type of instrument. Continue with <a
      href="Scenarios.html#PP5">Creating a printer profile</a>.<br>
    <br>
    <h4><a name="PP4"></a>Reading a print test chart using a scanner or
      camera<br>
    </h4>
    <br>
    Argyll supports using a scanner or even a camera as a substitute for
    a colorimeter. While a scanner or camera is no replacement for a
    color measurement instrument, it may give acceptable results in some
    situations, and may give better results than a generic profile for a
    printing device.<br>
    <br>
    The main limitation of the scanner-as-colorimeter approach are:<br>
    <br>
    * The scanner dynamic range and/or precision may not match the
    printers or what is required for a good profile.<br>
    * The spectral interaction of the scanner test chart and printer
    test chart with the scanner spectral response can cause color
    errors.<br>
    * Spectral differences caused by different black amounts in the
    print test chart can cause color errors. <br>
    * The scanner reference chart gamut may be much smaller than the
    printers gamut, making the scanner profile too inaccurate to be
    useful. <br>
    <br>
    As well as some of the above, a camera may not be suitable if it
    automatically adjusts exposure or white point when taking a picture,
    and this behavior cannot be disabled.<br>
    <br>
    The end result is often a profile that has a noticeable color cast,
    compared to a profile created using a colorimeter or spectrometer.<br>
    <br>
    <br>
    It is assumed that you have created a scanner or camera profile
    following the <a
      href="http://www.argyllcms.com/doc/Scenarios.html#PS1">procedure</a>
    outline above. For best possible results it is advisable to both
    profile the scanner or camera, and use it in scanning the printed
    test chart, in as "raw" mode as possible (i.e. using 16 bits per
    component images, if the scanner or camera is capable of doing so;
    not setting white or black points, using a fixed exposure etc.). It
    is generally advisable to create a LUT type input profile, and use
    the <a href="http://www.argyllcms.com/doc/colprof.html#u">-u</a>
    flag to avoid clipping scanned value whiter than the input
    calibration chart.<br>
    <br>
    Scan or photograph your printer chart (or charts) on the scanner or
    camera previously profiled. <big><span style="font-weight: bold;">The

























































        scanner or camera must be configured and used exactly the same
        as it was when it was profiled.</span></big><br>
    <br>
    I will assume the resulting scan/photo input file is called <span
      style="font-weight: bold;">PrinterB.tif</span> (or <span
      style="font-weight: bold;">PrinterB1.tif</span>, <span
      style="font-weight: bold;">PrinterB2.tif</span> etc. in the case
    of multiple charts). As with profiling the scanner or camera, the
    raster file need only be roughly cropped so as to contain the test
    chart.<br>
    <br>
    The scanner recognition files created when <span
      style="font-weight: bold;">printtarg</span> was run is assumed to
    be called <span style="font-weight: bold;">PrinterB.cht</span>.
    Using the scanner profile created previously (assumed to be called <span
      style="font-weight: bold;">scanner.icm</span>), the printer test
    chart scan patches are converted to CIE values using the <span
      style="font-weight: bold;">scanin</span> tool:<br>
    <br>
    <a href="scanin.html">scanin</a> <a href="scanin.html#v">-v</a> <a
      href="scanin.html#c">-c</a> <a href="scanin.html#cp1">PrinterB.tif</a>
    <a href="scanin.html#cp2">PrinterB.cht</a> <a
      href="scanin.html#cp3">scanner.icm</a> <a href="scanin.html#cp4">PrinterB</a><br>
    <br>
    If there were multiple test chart pages, the results would be
    accumulated page by page using the <a href="scanin.html#ca">-ca</a>
    option, ie., if there were 3 pages:<br>
    <br>
    <a href="scanin.html">scanin</a> <a href="scanin.html#v">-v</a> <a
      href="scanin.html#c">-c</a> <a href="scanin.html#cp1">PrinterB1.tif</a>
    <a href="scanin.html#cp2">PrinterB1.cht</a> <a
      href="scanin.html#cp3">scanner.icm</a> <a href="scanin.html#cp4">PrinterB</a><br>
    <a href="scanin.html">scanin</a> <a href="scanin.html#v">-v</a> <a
      href="scanin.html#ca">-ca</a> <a href="scanin.html#cp1">PrinterB2.tif</a>
    <a href="scanin.html#cp2">PrinterB2.cht</a> <a
      href="scanin.html#cp3">scanner.icm</a> <a href="scanin.html#cp4">PrinterB</a><br>
    <a href="scanin.html">scanin</a> <a href="scanin.html#v">-v</a> <a
      href="scanin.html#ca">-ca</a> <a href="scanin.html#cp1">PrinterB3.tif</a>
    <a href="scanin.html#cp2">PrinterB3.cht</a> <a
      href="scanin.html#cp3">scanner.icm</a> <a href="scanin.html#cp4">PrinterB</a><br>
    <br>
    Now that the <span style="font-weight: bold;">PrinterB.ti3</span>
    data has been obtained, the profile continue in the next section
    with <span style="font-weight: bold;">Creating a printer profile</span>.<br>
    <br>
    If you have any doubts about the correctness of the chart
    recognition, or the subsequent profile's delta E report is unusual,
    then use the scanin diagnostic flags <a href="scanin.html#d">-dipn</a>
    and examine the <span style="font-weight: bold;">diag.tif</span>
    diagnostic file.<br>
    <h4><a name="PP5"></a>Creating a printer profile<br>
    </h4>
    Creating an RGB based printing profile is very similar to creating a
    display device profile. For a CMYK printer, some additional
    information is needed to set the black generation.<br>
    <br>
    Where the resulting profile will be used conventionally (ie. using <a
      href="collink.html">collink</a> <a href="collink.html#s">-s</a>,
    or <a href="cctiff.html">cctiff</a> or most other "dumb" CMMs) it
    is important to specify that gamut mapping should be computed for
    the output (B2A) perceptual and saturation tables. This is done by
    specifying a device profile as the parameter to the <a
      href="colprof.html">colprof</a> <a href="colprof.html#S">-S</a>
    flag. When you intend to create a "general use" profile, it can be a
    good technique to specify the source gamut as the opposite type of
    profile to that being created, i.e. if a printer profile is being
    created, specify a display profile (e.g. sRGB) as the source gamut.
    If a display profile is being created, then specify a printer
    profile as the source (e.g. Figra, SWOP etc.).&nbsp; When linking to
    the profile you have created this way as the output profile, then
    use perceptual intent if the source is the opposite type, and
    relative colorimetric if it is the same type.<br>
    <br>
    "Opposite type of profile" refers to the native gamut of the device,
    and what its fundamental nature is, additive or subtractive. An
    emissive display will have additive primaries (R, G &amp; B), while
    a reflective print, will have subtractive primaries (C, M, Y &amp;
    possibly others), irrespective of what colorspace the printer is
    driven in (a printer might present an RGB interface, but internally
    this will be converted to CMY, and it will have a CMY type of
    gamut).&nbsp; Because of the complimentary nature of additive and
    subtractive device primary colorants, these types of devices have
    the most different gamuts, and hence need the most gamut mapping to
    convert from one colorspace to the other.<br>
    <br>
    If you are creating a profile for a specific purpose, intending to
    link it to a specific input profile, then you will get the best
    results by specifying that source profile as the source gamut.<br>
    <br>
    If a profile is only going to be used as an input profile, or is
    going to be used with a "smart" CMM (e.g. <a href="collink.html">collink</a>
    <a href="collink.html#g">-g</a> or <a href="collink.html#G">-G</a>),
then

























































    it can save considerable processing time and space if the -b flag is
    used, and the -S flag not used.<br>
    <br>
    For an RGB printer intended to print RGB originals, the following
    might be a typical profile usage:<br>
    <br>
    <a href="colprof.html">colprof</a> <a href="colprof.html#v">-v</a>
    <a href="colprof.html#E">-D"Printer A"</a> <a href="colprof.html#q">-qm</a>
    <a href="colprof.html#S">-S</a><a href="colprof.html#S"> sRGB.icm</a>
    <a href="colprof.html#c">-cmt</a> <a href="colprof.html#d">-dpp</a>
    <a href="colprof.html#p1">PrinterA</a><br>
    <br>
    or if you intent to print from Fogra, SWOP or other standard CMYK
    style originals:<br>
    <br>
    <a href="colprof.html">colprof</a> <a href="colprof.html#v">-v</a>
    <a href="colprof.html#E">-D"Printer A"</a> <a href="colprof.html#q">-qm</a>
    <a href="colprof.html#S">-S</a><a href="colprof.html#S">
      fogra39l.icm</a> <a href="colprof.html#c">-cmt</a> <a
      href="colprof.html#d">-dpp</a> <a href="colprof.html#p1">PrinterA</a><br>
    <br>
    If you know what colorspace your originals are in, use that as the
    argument to <span style="font-weight: bold;">-S</span>.<br>
    <br>
    If your viewing environment for the display and print doesn't match
    the ones implied by the <a href="colprof.html#c">-cmt</a> and <a
      href="colprof.html#d">-dpp</a> options, leave them out, and
    evaluate what, if any appearance transformation is appropriate for
    your environment at a later stage.<br>
    <br>
    Make sure you check the delta E report at the end of the profile
    creation, to see if the sample data and profile is behaving
    reasonably. Depending on the type of device, and the consistency of
    the readings, average errors of 5 or less, and maximum errors of 15
    or less would normally be expected. If errors are grossly higher
    than this, then this is an indication that something is seriously
    wrong with the device measurement, or profile creation.
    <h4><a name="PP6"></a>Choosing a black generation curve (and other
      CMYK printer options)<br>
    </h4>
    For a CMYK printer, it would be normal to specify the type of black
    generation, either as something simple, or as a specific curve. The
    documentation&nbsp; in <a href="colprof.html#k">colprof</a> for the
    details of the options.<span style="font-weight: bold;"><br>
      <br>
      Note</span> that making a good choice of black generation curve
    can affect things such as: how robust neutrals are given printer
    drift or changes in viewing lighting, how visible screening is, and
    how smooth looking the B2A conversion is.<br>
    <br>
    For instance, maximizing the level of K will mean that the neutral
    colors are composed of greater amounts of Black ink, and black ink
    retains its neutral appearance irrespective of printer behavior or
    the spectrum of the illuminant used to view the print. On the other
    hand, output which is dominantly from one of the color channels will
    tend to emphasize the screening pattern and any unevenness (banding
    etc.) of that channel, and the black channel in particular has the
    highest visibility. So in practice, some balance between the levels
    of the four channels is probably best, with more K if the screening
    is fine and a robust neutral balance is important, or less K if the
    screening is more visible and neutral balance is less critical. The
    levels of K at the edges of the gamut of the device will be fixed by
    the nature of the ink combinations that maximize the gamut (ie.
    typically zero ink for light chromatic colors, some combination for
    dark colors, and a high level of black for very dark near neutrals),
    and it is also usually important to set a curve that smoothly
    transitions to the K values at the gamut edges. Dramatic changes in
    K imply equally dramatic changes in CMY, and these abrupt
    transitions will reveal the limited precision and detail that can be
    captured in a lookup table based profile, often resulting in a
    "bumpy" looking output.<br>
    <br>
    If you want to experiment with the various black generation
    parameters, then it might be a good idea to create a preliminary
    profile (using <a href="colprof.html#q">-ql</a> <a
      href="colprof.html#b">-b</a> <a href="colprof.html#ni">-no</a>, <a
      href="colprof.html#no">-ni</a> and no <a href="colprof.html#S">-S</a>),
























































    and then used <a href="xicclu.html#g">xicclu</a> to explore the
    effect of the parameters.<br>
    <br>
    For instance, say we have our CMYK .ti3 file <span
      style="font-weight: bold;">PrinterB.ti3</span>. First we make a
    preliminary profile called <span style="font-weight: bold;">PrinterBt</span>:<br>
    <br>
    copy PrinterB.ti3 PrinterBt.ti3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (Use
    "cp" on Linux or OSX of course.)<br>
    <a href="colprof.html">colprof</a> <a href="colprof.html#v">-v</a>
    <a href="colprof.html#q">-qm</a> <a href="colprof.html#b">-b</a> <a
      href="colprof.html#c">-cmt</a> <a href="colprof.html#d">-dpp</a>
    <a href="colprof.html#p1">PrinterBt</a><br>
    <br>
    Then see what the minimum black level down the neutral axis can be.
    Note that we need to also set any ink limits we've decided on as
    well (coloprof defaulting to 10% less than the value recorded in the
    .ti3 file). In this example the test chart has a 300% total ink
    limit, and we've decided to use 290%:<br>
    <br>
    <a href="xicclu.html">xicclu</a> <a href="xicclu.html#g">-g</a> <a
      href="xicclu.html#k">-kz</a> <a href="xicclu.html#l">-l290</a> <a
      href="xicclu.html#f">-fif</a> <a href="xicclu.html#i">-ir</a> <a
      href="xicclu.html#p1">PrinterBt.icm</a><br>
    <br>
    Which might be a graph something like this:<br>
    <br>
    <img alt="Graph of CMYK neutral axis with minimum K"
      src="Kgraph1.jpg" style="width: 250px; height: 250px;"><br>
    <br>
    Note&nbsp; how the minimum black is zero up to 93% of the
    white-&gt;black L* curve, and then jumps up to 87%. This is because
    we've reached the total ink limit, and K then has to be substituted
    for CMY, to keep the total under the total ink limit.<br>
    <br>
    Then let's see what the maximum black level down the neutral axis
    can be:<br>
    <br>
    <a href="xicclu.html">xicclu</a> <a href="xicclu.html#g">-g</a> <a
      href="xicclu.html#k">-kx</a> <a href="xicclu.html#l">-l290</a> <a
      href="xicclu.html#f">-fif</a> <a href="xicclu.html#i">-ir</a> <a
      href="xicclu.html#p1">PrinterBt.icm</a><br>
    <br>
    Which might be a graph something like this:<br>
    <br>
    <img alt="Graph of CMYK neutral axis with maximum K"
      src="Kgraph2.jpg" style="width: 250px; height: 250px;"><br>
    <br>
    Note how the CMY values are fairly low up to 93% of the
    white-&gt;black L* curve (the low levels of CMY are helping set the
    neutral color), and then they jump up. This is because we've reach
    the point where black on it's own, isn't as dark as the color that
    can be achieved using CMY and K. Because the K has a dominant effect
    on the hue of the black, the levels of CMY are often fairly volatile
    in this region.<br>
    <br>
    Any K curve we specify must lie between the black curves of the
    above two graphs.<br>
    <br>
    Let's say we'd like to chose a moderate black curve, one that aims
    for about equal levels of CMY and K. We should also aim for it to be
    fairly smooth, since this will minimize visual artefacts caused by
    the limited fidelity that profile LUT tables are able to represent
    inside the profile.<br>
    <br>
    <img style="width: 340px; height: 258px;" alt="-k parameters"
      src="Kparams.jpg"><br>
    <br>
    <br>
    For minimum discontinuities we should aim for the curve to finish at
    the point it has to reach to satisfy the total ink limit at 87%
    curve and 93% black. For a first try we can simply set a straight
    line to that point: <br>
    <br>
    <a href="xicclu.html">xicclu</a> <a href="xicclu.html#g">-g</a> <a
      href="xicclu.html#k">-kp 0 0 .93 .87 1.0</a> <a
      href="xicclu.html#l">-l290</a> <a href="xicclu.html#f">-fif</a> <a
      href="xicclu.html#i">-ir</a> <a href="xicclu.html#p1">PrinterBt.icm</a><br>
    <br>
    <img alt="Graph of CMYK neutral axis with kp 0 0 1.0 1.0 1.0 -l290"
      src="Kgraph3.jpg" style="width: 250px; height: 250px;"><br>
    <br>
    The black "curve" hits the 93%/87% mark well, but is a bit too far
    above CMY, so we'll try making the black curve concave:<br>
    <br>
    <a href="xicclu.html">xicclu</a> <a href="xicclu.html#g">-g</a> <a
      href="xicclu.html#k">-kp </a><a href="xicclu.html#k">0 0 .93 .87
      0.65</a> <a href="xicclu.html#l">-l290</a> <a
      href="xicclu.html#f">-fif</a> <a href="xicclu.html#i">-ir</a> <a
      href="xicclu.html#p1">PrinterBt.icm</a><br>
    <br>
    <img alt="Graph of CMYK neutral axis with -kp 0 .05 1 .9 1 -l290"
      src="Kgraph4.jpg" style="width: 250px; height: 249px;"><br>
    <br>
    This looks just about perfect, so the the curve parameters can now
    be used to generate our real profile:<br>
    <br>
    <a href="colprof.html">colprof</a> <a href="colprof.html#v">-v</a>
    <a href="colprof.html#E">-D"Printer B"</a> <a href="colprof.html#q">-qm</a>
    <a href="colprof.html#k">-kp </a><a href="xicclu.html#k">0 0 .93
      .87 0.65</a> <a href="colprof.html#S">-S</a><a
      href="colprof.html#S"> sRGB.icm</a> <a href="colprof.html#c">-cmt</a>
    <a href="colprof.html#d">-dpp</a> <a href="colprof.html#p1">PrinterB</a><br>
    <br>
    and the resulting B2A table black curve can be checked using xicclu:<br>
    <br>
    <a href="xicclu.html">xicclu</a> <a href="xicclu.html#g">-g</a> <a
      href="xicclu.html#f">-fb</a> <a href="xicclu.html#i">-ir</a> <a
      href="xicclu.html#p1">PrinterB.icm</a><br>
    <br>
    <img style="width: 250px; height: 250px;" alt="sadsadas"
      src="Kgraph5.jpg"><br>
    <br>
    <br>
    <hr style="margin-left: 0px; margin-right: auto; width: 20%; height:
      2px;"><br>
    <span style="font-weight: bold;">Examples of other inkings:<br>
      <br>
    </span>A smoothed zero black inking:<br>
    <br>
    <a href="xicclu.html">xicclu</a> <a href="xicclu.html#g">-g</a> <a
      href="xicclu.html#k">-kp </a><a href="xicclu.html#k">0 .7 .93 .87
      1.0</a> <a href="xicclu.html#l">-l290</a> <a
      href="xicclu.html#f">-fif</a> <a href="xicclu.html#i">-ir</a> <a
      href="xicclu.html#p1">PrinterBt.icm</a><br>
    <br>
    <img style="width: 250px; height: 250px;" alt="sadsadas"
      src="Kgraph6.jpg"><br>
    <br>
    A low black inking:<br>
    <br>
    <a href="xicclu.html">xicclu</a> <a href="xicclu.html#g">-g</a> <a
      href="xicclu.html#k">-kp </a><a href="xicclu.html#k">0 0 .93 .87
      0.15</a> <a href="xicclu.html#l">-l290</a> <a
      href="xicclu.html#f">-fif</a> <a href="xicclu.html#i">-ir</a> <a
      href="xicclu.html#p1">PrinterBt.icm</a><br>
    <br>
    <img style="width: 250px; height: 250px;" alt="sadsadas"
      src="Kgraph7.jpg"><br>
    <br>
    <br>
    A high black inking:<br>
    <br>
    <a href="xicclu.html">xicclu</a> <a href="xicclu.html#g">-g</a> <a
      href="xicclu.html#k">-kp </a><a href="xicclu.html#k">0 0 .93 .87
      1.2</a> <a href="xicclu.html#l">-l290</a> <a
      href="xicclu.html#f">-fif</a> <a href="xicclu.html#i">-ir</a> <a
      href="xicclu.html#p1">PrinterBt.icm</a><br>
    <br>
    <img style="width: 250px; height: 250px;" alt="sadsadas"
      src="Kgraph8.jpg"><br>
    <br>
    <span style="font-weight: bold;"></span>
    <h4>Overriding the ink limit<br>
    </h4>
    Normally the total ink limit will be read from the <span
      style="font-weight: bold;">PrinterB.ti3</span> file, and will be
    set at a level 10% lower than the number used in creating the test
    chart values using <a href="targen.html#l">targen -l</a>. If you
    want to override this with a lower limit, then use the <a
      href="colprof.html#l">-l flag</a>.<br>
    <br>
    <a href="colprof.html">colprof</a> <a href="colprof.html#v">-v</a>
    <a href="colprof.html#E">-D"Printer B"</a> <a href="colprof.html#q">-qm</a>
    <a href="colprof.html#S">-S</a><a href="colprof.html#S"> sRGB.icm</a>
    <a href="colprof.html#c">-cmt</a> <a href="colprof.html#d">-dpp</a>
    <a href="colprof.html#k">-kr</a> <a href="xicclu.html#l">-l290</a>
    <a href="colprof.html#p1">PrinterB</a><br>
    <br>
    Make sure you check the delta E report at the end of the profile
    creation, to see if the profile is behaving reasonably.<br>
    <br>
    One way of checking that your ink limit is not too high, is to use "<span
      style="font-weight: bold;">xicc -fif -ia</span>" to check, by
    setting different ink limits using the <span style="font-weight:
      bold;">-l</span> option, feeding Lab = 0 0 0 into it, and checking
    the resulting&nbsp; black point. Starting with the ink limit used
    with <span style="font-weight: bold;">targen</span> for the test
    chart, reduce it until the black point starts to be affected. If it
    is immediately affected by any reduction in the ink limit, then the
    black point may be improved by increasing the ink limit used to
    generate the test chart and then re-print and re-measuring it,
    assuming other aspects such as wetness, smudging, spreading or
    drying time are not an issue.<br>
    <br>
    <hr style="width: 100%; height: 2px;"><br>
    <h3><a name="PC1"></a>Calibrating Printers<br>
    </h3>
    <span style="font-weight: bold;">Profiling</span> creates a
    description of how a device behaves, while <span
      style="font-weight: bold;">calibration</span> on the other hand is
    intended to <span style="text-decoration: underline;">change</span>
    how a device behaves. Argyll has the ability to create per-channel
    device space calibration curves for print devices, that can then be
    used to improve the behavior of of the device, making a subsequent
    profile fit the device more easily and also allow day to day
    correction of device drift without resorting to a full re-profile.<br>
    <br>
    <span style="font-weight: bold;">NOTE:</span> Because calibration
    adds yet another layer to the way color is processed, it is
    recommended that it not be attempted until the normal profiling
    workflow is established, understood and verified.<br>
    <h4><a name="PC2"></a>Calibrated print workflows</h4>
    There are two main workflows that printer calibration curves can be
    applied to:<br>
    <br>
    <span style="text-decoration: underline;">Workflow <span
        style="font-weight: bold;">with</span> native calibration
      capability</span>:<br>
    <br>
    Firstly the printer itself may have the capability of using per
    channel calibration curves. In this situation, the calibration
    process will be largely independent of profiling. Firstly the
    printer is configured to have both its color management and
    calibration disabled (the latter perhaps achieved by loading linear
    calibration curves), and a print calibration test chart that
    consists of per channel color wedges is printed. The calibration
    chart is read and the resulting .ti3 file converted into calibration
    curves by processing it using <span style="font-weight: bold;">printcal</span>.
    The calibration is then installed into the printer. Subsequent
    profiling will be performed on the <span style="text-decoration:
      underline;">calibrated</span> printer (ie. the profile test chart
    will have the calibration curves applied to it by the printer, and
    the resulting ICC profile will represent the behavior of the
    calibrated printer.)<br>
    <br>
    <span style="text-decoration: underline;">Workflow <span
        style="font-weight: bold;">without</span> native calibration
      capability</span>:<br>
    <br>
    The second workflow is one in which the printer has no calibration
    capability itself. In this situation, the calibration process will
    have to be applied using the ICC color management tools, so careful
    coordination with profiling is needed. Firstly the printer is
    configured to have its color management disabled, and a print
    calibration test chart that consists of per channel color wedges is
    printed. The calibration chart is converted into calibration curves
    by reading it and then processing the resultant .ti3 using <span
      style="font-weight: bold;">printcal</span>,. During the subsequent
    <span style="text-decoration: underline;">profiling</span>, the
    calibration curves will need to be applied to the profile test chart
    in the process of using <span style="font-weight: bold;">printtarg</span>.
    Once the the profile has been created, then in subsequent printing
    the calibration curves will need to be applied to an image being
    printed either explicitly when using <span style="font-weight:
      bold;">cctiff</span> to apply color profiles <span
      style="text-decoration: underline;">and</span> calibration, <span
      style="font-weight: bold;">OR</span> by creating a version of the
    profile that has had the calibration curves incorporated into it
    using the <span style="font-weight: bold;">applycal</span> tool.
    The latter is useful when some CMM (color management module) other
    than <span style="font-weight: bold;">cctiff </span>is being used.<br>
    <br>
    Once calibration aim targets for a particular device and mode
    (screening, paper etc.) have been established, then the printer can
    be re-calibrated at any time to bring its per channel behavior back
    into line if it drifts, and the new calibration curves can be
    installed into the printer, or re-incorporated into the profile.
    &nbsp;
    <h4><a name="PC3"></a>Creating a print calibration test chart</h4>
    The first step is to create a print calibration test chart. Since
    calibration only creates per-channel curves, only single channel
    step wedges are required for the chart. The main choice is the
    number of steps in each wedge. For simple fast calibrations perhaps
    as few as 20 steps per channel may be enough, but for a better
    quality of calibration something like 50 or more steps would be a
    better choice.<br>
    <br>
    Let's consider two devices in our examples, "PrinterA" which is an
    "RGB" printer device, and "PrinterB" which is CMYK. In fact there is
    no such thing as a real RGB printer, since printers use white media
    and the colorant must subtract from the light reflected on it to
    create color, but the printer itself turns the incoming RGB into the
    native print colorspace, so for this reason we are careful to tell
    targen to use the "Print RGB" colorspace, so that it knows to create
    step wedges from media white to full colorant values.<br>
    <br>
    For instance, to create a 50 steps per channel calibration test
    chart for our RGB and CMYK devices, the following would be
    sufficient:<br>
    <br>
    <a href="targen.html">targen</a> <a href="targen.html#v">-v</a>
    &nbsp;<a href="targen.html#d">-d2</a> <a href="targen.html#s">-s50</a>
    <a href="targen.html#e">-e3</a> <a href="targen.html#f">-f0</a> <a
      href="targen.html#p1">PrinterA_c</a><br>
    <br>
    <a href="targen.html">targen</a> <a href="targen.html#v">-v</a>
    &nbsp;<a href="targen.html#d">-d4</a> <a href="targen.html#s">-s50</a>
    <a href="targen.html#e">-e4</a> <a href="targen.html#f">-f0</a> <a
      href="targen.html#p1">PrinterB_c</a><br>
    <a href="targen.html#p1"></a><br>
    For an outline of how to then print and read the resulting test
    chart, see&nbsp; <a href="Scenarios.html#PP2b">Printing a print
      profile test chart</a>, and <a href="Scenarios.html#PP3">Reading
      a print test chart using an instrument</a>. Note that the printer
    must be in an un-profiled and un-calibrated mode when doing this
    print. Having done this, there will be a PrinterA.ti3 or
    PrinterB.ti3 file containing the step wedge calibration chart
    readings.<br>
    <br>
    <span style="font-weight: bold;">NOTE</span> that if you are
    calibrating a raw printer driver, and there is considerable dot
    gain, then you may want to use the <a href="targen.html#p">-p</a>
    parameter to adjust the test chart point distribution to spread them
    more evenly in perceptual space, giving more accurate control over
    the calibration. Typically this will be a value greater than one for
    a device that has dot gain, e.g. values of 1.5, 2.0 or 2.5 might be
    good places to start. You can do a preliminary calibration and use
    the verbose output of printcal to recommend a suitable value for <span
      style="font-weight: bold;">-p</span>.<br>
    <h4><a name="PC4"></a>Creating a printer calibration<br>
    </h4>
    The <a href="printcal.html">printcal</a> tool turns a calibration
    chart <a href="File_Formats.html#.ti3">.ti3</a> file into a <a
      href="File_Formats.html#.cal">.cal</a> file. It has three main
    operating modes:- Initial calibration, Re-Calibration, and
    Verification. (A fourth mode, "Imitation" is very like Initial
    Calibration, but is used for establishing a calibration target that
    a similar printer can attempt to imitate.)<br>
    <br>
    The distinction between Initial Calibration and Re-Calibration is
    that in the initial calibration we establish the "aim points" or
    response we want out of the printer after calibration. There are
    three basic parameters to set this for each channel: Maximum level,
    minimum level, and curve shape.<br>
    <br>
    By default the maximum level will be set using a heuristic which
    attempts to pick the point when there is diminishing returns for
    applying more colorant. This can be overridden using the <span
      style="font-weight: bold;">-x# percent</span> option, where <span
      style="font-weight: bold;">#</span> represents the choice of
    channel this will be applied to. The parameter is the percentage of
    device maximum. <br>
    <br>
    The minimum level defaults to 0, but can be overridden using the <span
      style="font-weight: bold;">-n# deltaE</span> option. A minimum of
    0 means that zero colorant will correspond to the natural media
    color, but it may be desirable to set a non-pure media color using
    calibration for the purposes of emulating some other media. The
    parameter is in Delta E units.<br>
    <br>
    The curve shape defaults to being perceptually uniform, which means
    that even steps of calibrated device value result in perceptually
    even color steps. In some situations it may be desirable to alter
    this curve (for instance when non color managed output needs to be
    sent to the calibrated printer), and a simple curve shape target can
    be set using the <span style="font-weight: bold;">-t# percent</span>
    parameter. This affects the output value at 50% input value, and
    represents the percentage of perceptual output. By default it is 50%
    perceptual output for 50% device input.<br>
    <br>
    Once a device has been calibrated, it can be re-calibrated to the
    same aim target.<br>
    <br>
    Verification uses a calibration test chart printed through the
    calibration, and compares the achieved response to the aim target.<br>
    <br>
    The simplest possible way of creating the <span style="font-weight:
      bold;">PrinterA.cal</span> file is:<br>
    <br>
    &nbsp; <a href="printcal.html">printcal</a> <a
      href="printcal.html#i">-i</a> <a href="colprof.html#p2">PrinterA_c</a><br>
    <br>
    For more detailed information, you can add the <span
      style="font-weight: bold;">-v</span> and <span
      style="font-weight: bold;">-p</span> flags:<br>
    <br>
    &nbsp; <a href="printcal.html">printcal</a> <a
      href="printcal.html#v">-v</a> <a href="printcal.html#p">-p</a> <a
      href="printcal.html#i">-i</a> <a href="colprof.html#p2">PrinterB_c</a><br>
    <br>
    (You will need to select the plot window and hit a key to advance
    past each plot).<br>
    <br>
    For re-calibration, the name of the previous calibration file will
    need to be supplied, and a new calibration<br>
    file will be created:<br>
    <br>
    &nbsp; <a href="printcal.html">printcal</a> <a
      href="printcal.html#v">-v</a> <a href="printcal.html#p">-p</a> <a
      href="printcal.html#r">-r</a> <a href="colprof.html#p1">PrinterB_c_old</a>
    <a href="colprof.html#p2">PrinterB_c_new</a><br>
    <br>
    Various aim points are normally set automatically by <span
      style="font-weight: bold;">printcal</span>, but these can be
    overridden using the <a href="colprof.html#x">-x</a>, <a
      href="colprof.html#n">-n</a> and <a href="colprof.html#t">-t</a>
    options. e.g. say we wanted to set the maximum ink for Cyan to 80%
    and Black to 95%, we might use:<br>
    <br>
    &nbsp; <a href="printcal.html">printcal</a> <a
      href="printcal.html#v">-v</a> <a href="printcal.html#p">-p</a> <a
      href="printcal.html#i">-i</a> <a href="colprof.html#x">-xc 80</a>
    <a href="colprof.html#x">-xk 95</a> <a href="colprof.html#p2">PrinterB_c</a><br>
    <br>
    <a href="colprof.html#p2"></a>
    <h4><a name="PC5"></a>Using a printer calibration</h4>
    The resulting calibration curves can be used with the following
    other Argyll tools:<br>
    <br>
    &nbsp;&nbsp;&nbsp; <a href="printtarg.html#K">printtarg</a>&nbsp;&nbsp;&nbsp;&nbsp;
To
apply
calibration
to
a
profile
test
chart,

























































    and/or to have it included in .ti3 file.<br>
    &nbsp;&nbsp;&nbsp; <a href="cctiff.html#p2">cctiff</a>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
To
apply
color
management
and
calibration
to
an

























































    image file.<br>
    &nbsp;&nbsp;&nbsp; <a href="applycal.html#p1">applycal</a>&nbsp;&nbsp;&nbsp;&nbsp;

























































    To incorporate calibration into an ICC profile.<br>
    &nbsp;&nbsp;&nbsp; <a href="chartread.html#I">chartread</a>&nbsp;&nbsp;
To
override
the
calibration
assumed
when
reading
a

























































    profile chart.<br>
    <br>
    <br>
    In a workflow <span style="font-weight: bold;">with</span> native
    calibration capability, the calibration curves would be used with
    printarg during subsequent <span style="font-weight: bold;">profiling</span>
    so that any ink limit calculations will reflect final device values,
    while not otherwise using the calibration within the ICC workflow:<br>
    <br>
    &nbsp;&nbsp;&nbsp; <a href="printtarg.html">printtarg</a> <a
      href="printtarg.html#v">-v</a> <a href="printtarg.html#i">-ii1</a>
    <a href="printtarg.html#p">-pA4</a> <a href="printtarg.html#I">-I
      PrinterA_c.cal</a> <a href="printtarg.html#p1">PrinterA</a><br>
    <br>
    This will cause the .ti2 and resulting .ti3 and ICC profiles to
    contain the calibration curves, allowing all the tools to be able to
    compute final device value ink limits. The calibration curves must
    also of course be installed into the printer. The means to do this
    is currently outside the scope of Argyll (ie. either the print
    system needs to be able to understand Argyll CAL format files, or
    some tool will be needed to convert Argyll CAL files into the
    printer calibration format).<br>
    <br>
    <br>
    In a workflow <span style="font-weight: bold;">without</span>
    native calibration capability, the calibration curves would be used
    with printarg to <span style="text-decoration: underline;">apply</span>
    the calibration to the test patch samples during subsequent <span
      style="font-weight: bold;">profiling</span>, as well as embedding
    it in the resulting .ti3 to allow all the tools to be able to
    compute final device value ink limits:<br>
    <br>
    &nbsp;&nbsp;&nbsp; <a href="printtarg.html">printtarg</a> <a
      href="printtarg.html#v">-v</a> <a href="printtarg.html#i">-ii1</a>
    <a href="printtarg.html#p">-pA4</a> <a href="printtarg.html#K">-K
      PrinterA_c.cal</a> <a href="printtarg.html#p1">PrinterA</a><br>
    <a href="cctiff.html#p4"></a><br>
    To apply calibration to an ICC profile, so that a calibration
    unaware CMM can be used:<br>
    <br>
    &nbsp;&nbsp;&nbsp; <a href="applycal.html">applycal</a> <a
      href="applycal.html#p1">PrinterA.cal</a> <a
      href="applycal.html#p2">PrinterA.icm</a> <a
      href="applycal.html#p3">PrinterA_cal.icm</a><br>
    <br>
    To apply color management and calibration to a raster image:<br>
    <br>
    &nbsp;&nbsp;&nbsp; <a href="file:///D:/src/argyll/doc/cctiff.html">cctiff</a>
    <a href="file:///D:/src/argyll/doc/cctiff.html#p1">Source.icm</a> <a
      href="file:///D:/src/argyll/doc/cctiff.html#p1">PrinterA.icm</a> <a
      href="file:///D:/src/argyll/doc/cctiff.html#p2">PrinterA_c.cal</a>
    <a href="file:///D:/src/argyll/doc/cctiff.html#p3">infile.tif</a> <a
      href="file:///D:/src/argyll/doc/cctiff.html#p4">outfile.tif</a><br>
    <br>
    or<br>
    <br>
    &nbsp;&nbsp;&nbsp; <a href="file:///D:/src/argyll/doc/cctiff.html">cctiff</a>
    <a href="file:///D:/src/argyll/doc/cctiff.html#p1">Source.icm</a> <a
      href="file:///D:/src/argyll/doc/cctiff.html#p1">PrinterA_c.icm</a>
    <a href="file:///D:/src/argyll/doc/cctiff.html#p3">infile.tif</a> <a
      href="file:///D:/src/argyll/doc/cctiff.html#p4">outfile.tif</a><br>
    <br>
    [ Note that cctiff will also process JPEG raster images. ]<br>
    <br>
    Another useful tool is <a href="synthcal.html">synthcal</a>, that
    allows creating linear or synthetic calibration files for disabling
    calibration or testing.<br>
    Similarly, <a href="fakeread.html">fakeread</a> also supports
    applying calibration curves and embedding them in the resulting .ti3
    file<br>
    <br>
    If you want to create a pre-conditioning profile for use with <a
      href="targen.html#c">targen -c</a>, then use the PrinterA.icm
    profile, <b>NOT</b> PrinterA_c.icm that has calibration curves
    applied.<br>
    <h4><a name="PC6"></a>How profile ink limits are handled when
      calibration is being used.</h4>
    Even though the profiling process is carried out on top of the
    linearized device, and the profiling is generally unaware of the
    underlying non-linearized device values, an exception is made in the
    calculation of ink limits during profiling. This is made possible by
    including the calibration curves in the profile charts .ti2 and
    subsequent .ti3 file and resulting ICC profile <span
      style="font-weight: bold;">'targ'</span> text tag, by way of the <span
      style="font-weight: bold;">printtarg</span> <span
      style="font-weight: bold;">-I</span> or <span style="font-weight:
      bold;">-K</span> options. This is done on the assumption that the
    physical quantity of ink is what's important in setting the ink
    limit, and that the underlying non-linearized device values
    represent such a physical quantity.<br>
    <br>
    <br>
    <hr size="2" width="100%">
    <h3><a name="LP1"></a>Linking Profiles</h3>
    Two device profiles can be linked together to create a device link
    profile, than encapsulates a particular device to device transform.
    Often this step is not necessary, as many systems and tools will
    link two device profiles "on the fly", but creating a device link
    profile gives you the option of using "smart CMM" techniques, such
    as true gamut mapping, improved inverse transform accuracy, tailored
    black generation and ink limiting.<br>
    <br>
    The overall process is to link the input space and output space
    profiles using <a href="collink.html">collink</a>, creating a
    device to device link profile. The device to device link profile can
    then be used by cctiff (or other ICC device profile capable tools),
    to color correct a raster files.<br>
    <br>
    Three examples will be given here, showing the three different modes
    than <span style="font-weight: bold;">collink</span> supports.<br>
    <br>
    In <a href="collink.html#s">simple mode</a>, the two profiles are
    linked together in a similar fashion to other <span
      style="font-weight: bold;">CMMs</span> simply using the forward
    and backwards color transforms defined by the profiles. Any gamut
    mapping is determined by the content of the tables within the two
    profiles, together with the particular intent chosen. Typically the
    same intent will be used for both the source and destination
    profile:<br>
    <br>
    <a href="collink.html">collink</a> <a href="collink.html#v">-v</a>
    <a href="collink.html#q">-qm</a> <a href="collink.html#s">-s</a> <a
      href="collink.html#si">-ip</a> <a href="collink.html#so">-op</a>
    <a href="collink.html#p1">SouceProfile.icm</a> <a
      href="collink.html#p2">DestinationProfile.icm</a> <a
      href="collink.html#p3">Source2Destination.icm</a><br>
    <br>
    <br>
    In <a href="collink.html#g">gamut mapping mode</a>, the
    pre-computed intent mappings inside the profiles are not used, but
    instead the gamut mapping between source and destination is tailored
    to the specific gamuts of the two profiles, and the intent parameter
    supplied to <span style="font-weight: bold;">collink</span>.
    Additionally, source and destination viewing conditions should be
    provided, to allow the color appearance space conversion to work as
    intended. The colorimetric B2A table in the destination profile is
    used, and this will determine any black generation and ink limiting:<br>
    <br>
    <a href="collink.html">collink</a> <a href="collink.html#v">-v</a>
    <a href="collink.html#q">-qm</a> <a href="collink.html#g">-g</a> <a
      href="collink.html#si">-ip</a> <a href="collink.html#c">-cmt</a>
    <a href="collink.html#d">-dpp</a> <a href="collink.html#p1">MonitorSouceProfile.icm</a>
    <a href="collink.html#p2">DestinationProfile.icm</a> <a
      href="collink.html#p3">Source2Destination.icm</a><br>
    <br>
    [ If your viewing environment for the display and print doesn't
    match the ones implied by the <a href="colprof.html#c">-cmt</a> and
    <a href="colprof.html#d">-dpp</a> options, leave them out, and
    evaluate what, if any appearance transformation is appropriate for
    your environment at a later stage. ]<br>
    <br>
    In <a href="collink.html#G">inverse output table gamut mapping mode</a>,
    the pre-computed intent mappings inside the profiles are not used,
    but instead the gamut mapping between source and destination is
    tailored to the specific gamuts of the two profiles, and the intent
    parameter supplied to <span style="font-weight: bold;">collink</span>.
    In addition, the B2A table is <span style="font-weight: bold;">not</span>
    used in the destination profile, but the A2B table is instead
    inverted, leading to improved transform accuracy, and in CMYK
    devices, allowing the ink limiting and black generation parameters
    to be set:<br>
    <br>
    For a CLUT table based RGB printer destination profile, the
    following would be appropriate:<br>
    <br>
    <a href="collink.html">collink</a> <a href="collink.html#v">-v</a>
    <a href="collink.html#q">-qm</a> <a href="collink.html#G">-G</a> <a
      href="collink.html#si">-ip</a> <a href="collink.html#c">-cmt</a>
    <a href="collink.html#d">-dpp</a> <a href="collink.html#p1">MonitorSouceProfile.icm</a>
    <a href="collink.html#p2">RGBDestinationProfile.icm</a> <a
      href="collink.html#p3">Source2Destination.icm</a><br>
    <br>
    For a CMYK profile, the total ink limit needs to be specified (a
    typical value being 10% less than the value used in creating the
    device test chart), and the type of black generation also needs to
    be specified:<br>
    <br>
    <a href="collink.html">collink</a> <a href="collink.html#v">-v</a>
    <a href="collink.html#q">-qm</a> <a href="collink.html#G">-G</a> <a
      href="collink.html#si">-ip</a> <a href="collink.html#c">-cmt</a>
    <a href="collink.html#d">-dpp</a> <a href="collink.html#l">-l250</a>
    <a href="collink.html#k">-kr</a> <a href="collink.html#p1">MonitorSouceProfile.icm</a>
    <a href="collink.html#p2">CMYKDestinationProfile.icm</a> <a
      href="collink.html#p3">Source2Destination.icm</a><br>
    <br>
    Note that you should set the source (<a href="collink.html#c">-c</a>)
    and destination (<a href="collink.html#d">-d</a>) viewing conditions
    for the type of device the profile represents, and the conditions
    under which it will be viewed.<br>
    <br>
    <h3><a name="LP3"></a>Image dependent gamut mapping using device
      links<br>
    </h3>
    When images are stored in large gamut colorspaces (such as. L*a*b*
    or ProPhoto, etc.), then using the colorspace gamut as the source
    gamut for gamut mapping is generally a bad idea, as it leads to
    overly compressed and dull images. The correct approach is to use a
    source gamut that represents the gamut of the images themselves.
    This can be created using tiffgamut, and an example workflow is as
    follows:<br>
    <br>
    <a href="tiffgamut.html">tiffgamut</a> -f80 -pj -cmt ProPhoto.icm
    image.tif<br>
    <br>
    <a href="collink.html">collink</a> <a href="collink.html#v">-v</a>
    <a href="collink.html#q">-qh</a> <a href="collink.html#G">-G</a> <a
      href="collink.html#Gp">image.gam</a> <a href="collink.html#si">-ip</a>
    <a href="collink.html#c">-cmt</a> <a href="collink.html#d">-dpp</a>
    <a href="collink.html#p1">ProPhoto.icm</a> <a
      href="file:///D:/src/argyll/doc/collink.html#p2">RGBDestinationProfile.icm</a>
    <a href="file:///D:/src/argyll/doc/collink.html#p3">Source2Destination.icm</a><br>
    <br>
    <a href="file:///D:/src/argyll/doc/cctiff.html">cctiff</a> <a
      href="file:///D:/src/argyll/doc/cctiff.html#p1">Source2Destination.icm</a>
    <a href="file:///D:/src/argyll/doc/cctiff.html#p3">image.tif</a> <a
      href="file:///D:/src/argyll/doc/cctiff.html#p4">printfile.tif</a><br>
    <br>
    The printfile.tif is then send to the printer without color
    management, (i.e. in the same way the printer characterization test
    chart was printed), since it is in the printers native colorspace.<br>
    <br>
    You can adjust how conservatively the image gamut is preserved using
    the tiffgamut -f parameter. Omitting it or using a larger value (up
    to 100) preserves the color gradations of even the lesser used
    colors, at the cost of compressing the gamut more.<br>
    Using a smaller value will preserve the saturation of the most
    popular colors, at the cost of not preserving the color gradations
    of less popular colors.<br>
    <br>
    You can create a gamut that covers a set of source images by
    providing more than one image file name to tiffgamut. This may be
    more efficient for a group of related images, and ensures that
    colors are transformed in exactly the same way for all of the
    images.<br>
    <br>
    The arguments to collink should be appropriate for the output device
    type - see the collink examples in the above section.<br>
    <h3><a name="LP2"></a>Soft Proofing Link</h3>
    Often it is desirable to get an idea what a particular devices
    output will look like using a different device. Typically this might
    be trying to evaluate print output using a display. Often it is
    sufficient to use an absolute or relative colorimetric transform
    from the print device space to the display space, but while these
    provide a colorimetric preview of the result, they do not take into
    account the subjective appearance differences due to the different
    device conditions. It can therefore be useful to create a soft proof
    appearance transform using collink:<br>
    <br>
    <a href="collink.html">collink</a> <a href="collink.html#v">-v</a>
    <a href="collink.html#q">-qm</a> <a href="collink.html#G">-G</a> <a
      href="collink.html#si">-ila</a> <a href="collink.html#c">-cpp</a>
    <a href="collink.html#d">-dmt</a> <a href="collink.html#l">-t250</a>&nbsp;<a
      href="collink.html#k"></a><a href="collink.html#p1">CMYKDestinationProfile.icm</a>
    <a href="collink.html#p2">MonitorProfile.icm</a> <a
      href="collink.html#p3">SoftProof.icm</a><br>
    <br>
    We use the Luminance matched appearance intent, to preserve the
    subjective apperance of the target device, which takes into account
    the viewing conditions and assumes adaptation to the differences in
    the luminence range, but otherwise not attempting to compress or
    change the gamut.<br>
    <br>
    If your viewing environment for the display and print doesn't match
    the ones implied by the <a href="collink.html#c">-cpp</a> and <a
      href="collink.html#d">-dmt</a> options, then either leave them out
    or substitute values that do match your environment.<br>
    &nbsp;
    <hr size="2" width="100%"><br>
    <h3><a name="TR1"></a>Transforming colorspaces of raster files</h3>
    Although a device profile or device link profile may be useful with
    other programs and systems, Argyll provides the tool <a
      href="cctiff.html">cctiff</a> for directly applying a device to
    device transform to a <a href="File_Formats.html#TIFF">TIFF</a> or
    <a href="File_Formats.html#JPEG">JPEG</a> raster file. The cctiff
    tool is capable of linking an arbitrary sequence of device profiles,
    device links, abstract profiles and calibration curves. Each device
    profile can be preceded by the <span style="font-weight: bold;">-i</span>
    option to indicate the intent that should be used. Both 8 and 16 bit
    per component files can be handled, and up to 8 color channels. The
    color transform is optimized to perform the overall transformation
    rapidly.<br>
    <br>
    If a device link is to be used, the following is a typical example:<br>
    <br>
    <a href="cctiff.html">cctiff</a> <a href="cctiff.html#p1">Source2Destination.icm</a>
    <a href="cctiff.html#p3">infile.tif</a> <a href="cctiff.html#p4">outfile.tif</a><br>
    or<br>
    <a href="cctiff.html">cctiff</a> <a href="cctiff.html#p1">Source2Destination.icm</a>
    <a href="cctiff.html#p3">infile.jpg</a> <a href="cctiff.html#p4">outfile.jpg</a><br>
    <br>
    <i><br>
    </i>If a source and destination profile are to be used, the
    following would be a typical example:<br>
    <br>
    <a href="cctiff.html"> cctiff</a>&nbsp; <a href="cctiff.html#i">-ip</a>
    <a href="cctiff.html#p1i">SourceProfile.icm</a> <a
      href="cctiff.html#i">-ip</a> <a href="cctiff.html#p1o">DestinationProfile.icm</a>
    <a href="cctiff.html#p3">infile.tif</a> <a href="cctiff.html#p4">outfile.tif</a><br>
    or<br>
    <a href="cctiff.html"> cctiff</a>&nbsp; <a href="cctiff.html#i">-ip</a>
    <a href="cctiff.html#p1i">SourceProfile.icm</a> <a
      href="cctiff.html#i">-ip</a> <a href="cctiff.html#p1o">DestinationProfile.icm</a>
    <a href="cctiff.html#p3">infile.jpg</a> <a href="cctiff.html#p4">outfile.jpg</a><br>
    <br>
    <br>
    <hr size="2" width="100%"><br>
    <h3><a name="TV1"></a>Creating Video Calibration 3DLuts</h3>
    Video calibration typically involves trying to make your actual
    display device emulate an ideal video display, one which matches
    what your Video media was intended to be displayed on. An ICC device
    link embodies the machinery to do exactly this, to take device
    values in the target source colorspace and transform them into an
    actual output device colorspace. In the Video and Film industries a
    very similar, but less sophisticated means of doing this is to use
    3DLuts, which come in a multitude of different format. ICC device
    links have the advantage of being a superset of 3dLuts, encapsulated
    in a standard file format.<br>
    <br>
    To facilitate Video calibration of certain Video systems, ArgyllCMS
    supports some 3DLut output options as part of <a
      href="collink.html">collink</a>.<br>
    <br>
    What follows here is an outline of how to create Video calibration
    3DLuts using ArgyllCMS. First comes a general discussion of various
    aspects of video device links/3dLuts, and followed with some
    specific advice regarding the systems that ArgyllCMS supports. Last
    is some recommended scenarios for verifying the quality of Video
    calibration achieved.<br>
    <h5>1) How to display test patches.<br>
    </h5>
    Argyll's normal test patch display will be used by default, as long
    as any video encoding range considerations are dealt with (see
    Signal encoding below).<br>
    <br>
    An alternative when working with MadVR V 0.86.9 or latter, is to use
    the madTPG to display the patches in which case the MadVR video
    encoding range setting will operate. This can give some quality
    benefits due to MadVR's use of dithering. To display patches using
    MadVR rather than Argyll, start madTPG and then use the option "<b>-d




      madvr</b>" in dispcal, dispread and dispwin. Leave the MadTPG
    "VideoLUT" and "3dluts" buttons in their default&nbsp; (enabled)
    state, as the various tools will automatically take care of
    disabling the 3dLut and/or calibration curves as needed.<br>
    <br>
    Another option is to use a <a
      href="http://en.wikipedia.org/wiki/Chromecast">ChromeCast</a>
    using the option "<b>-dcc</b>" in dispcal, dispread and dispwin.
    Note that the ChromeCast as a test patch source is probably the<b>
      least accurate</b> of your choices, since it up-samples the test
    patch and transforms from RGB to YCC and back, but should be
    accurate within ± 1 bit. You may have to modify any firewall to
    permit port 8081 to be accessed on your machine if it falls back to
    the Default receiver (see <a href="Installing.html">installation
      instructions</a> for your platform).
    <h5>2) White point calibration &amp; neutral axis calibration.</h5>
    A Device Link is capable of embodying all aspects of the
    calibration, including correcting the white point and neutral axis
    behavior of the output device, but making such a Link just from two
    ICC profile requires the use of Absolute Colorimetric intent during
    linking, and this reduces flexibility. In addition, a typical ICC
    device profile may not capture the neutral axis behavior quite as
    well as an explicit calibration, since it doesn't sample the
    displays neutral axis behaviour in quite as much detail. It is often
    desirable therefore, to calibrate the display device so as to have
    the specific white point desired so that one of the white point
    relative linking intents can be used, and to improve the displays
    general neutral axis behavior so that subsequent profiling works to
    best advantage. In summary, there are basically 4 options in
    handling white point &amp; neutral axis calibration:<br>
    <ul>
      <li>Don't bother correcting the white point. Most displays are
        close to the typical D65 target, and our eyes adapt to the white
        automatically unless it is very far from the daylight locus or
        we have something else to refer to. If this approach is taken,
        then display profiling and linking can ignore calibration, and
        one of the non Absolute Colorimetric intents (such as Relative
        Colorimetric) is chosen during profile linking. It is wise to
        make sure that the video card VideoLUTs are set to some known
        state (ie. linear using "dispwin -c" , or set by a an installed
        ICC display profile) though.<br>
      </li>
      <li>Calibrate the white point and linearise the neutral axis using
        the display controls. Many TV's have internal calibration
        controls that allow setting the white point, and possibly the
        neutral axis response. Either a dedicated Video calibration
        package could be used, or ArgyllCMS <a href="dispcal.html">dispcal</a>'s















        interactive adjustment mode can be used to set the white point.
        Note that while adjusting the neutral axis for neutrality may
        help, the Device Link will override the transfer curve
        characteristic of the calibrated display, so aiming for a
        transfer curve approximately the same as the target and
        reasonably perceptually linear is all that is required. If this
        approach is taken, then display profiling and linking can ignore
        calibration, and one of the non Absolute Colorimetric intents is
        chosen during profile linking. It is wise to make sure that the
        video card VideoLUTs are set to some known state&nbsp; though.</li>
      <li>[<b>Recommended</b>] Calibrate the white point and neutral
        axis using ArgyllCMS <a href="dispcal.html">dispcal</a>. Since
        the Device Link will override the calibrated transfer curve
        characteristic of the display, there there may be no point in
        doing much more than a medium calibration, and choosing a
        standard that has a straight segment from black, such as L*a*b*,
        sRGB, Rec709 or SMPTE240 curve. The exact shape of the
        calibration curve is not critically important, as the profiling
        and 3dLut will set the final response. If this approach is
        taken, then the resulting calibration file should be provided to
        dispread as the <a href="dispcal.html#k">-k parameter</a> or <a
          href="dispcal.html#K">-K parameter</a>.&nbsp; See also below <b>Choice












          of where to apply display per channel calibration curves.</b></li>
      <li>Choose one of the Absolute Colorimetric intents in collink
        (ie. -i aw). This greatly reduces flexibility, and may not be
        quite as accurate as an explicit calibration.</li>
    </ul>
    If an explicit calibration is used, then it is a good idea to add
    some test points down the neutral axis when profiling (targen <a
      href="targen.html#g">-g parameter</a>). <br>
    <br>
    <b>3) Choice of where to apply display per channel calibration
      curves</b><br>
    <br>
    If calibration curves are going to be used, then it needs to be
    decided where they will be applied in the video processing chain.
    There are two options:<br>
    <br>
    <b>a)</b> Install the calibration curves in the playback system. On
    a PC the display, this can be done by loading the calibration curves
    into the Video Card temporarily using "dispwin calibration.cal", or
    installing the ICC profile into the system persistently using
    something like "<a href="dispwin.html#I">dispwin -I profile.icm</a>",<br>
    or when using MadVR 0.86.9 or latter by creating a 3dLut with
    appended calibration curves using <a href="collink#H">-H
      display.cal</a>.<br>
    <br>
    <b>b)</b> The calibration can be incorporated into the Device
    Link/3dLUT by providing it to collink as the <a
      href="collink.html#a">-a display.cal</a>. This is the only option
    if the video display path does not have some separate facility to
    handle calibration curves. Note that if the playback system has
    graphic card VideoLUTs then they will have to be set to a defined
    consistent state such as linear. When using MadVR 0.86.9 or latter
    this will be done automatically since the -a option will append a
    linear set of calibration curves to the 3dLut.<br>
    <br>
    The choice is dictated by a number of considerations:<br>
    <ul>
      <li>Does the video playback path have a facility for installing
        the calibration curves ? If playing back system is a PC, then
        typically the Graphics Card supports 1D VideoLUTs, thereby
        making a) a possible choice.<br>
      </li>
      <li>Does the video playback <u>always</u> play back through the
        Video Card VideoLUTs ? Some systems do not apply VIdeoLUTs to
        things like overlay plane rendering. If not, then you need to
        choose b), but also make sure that if it does use the Video Card
        VideoLUTs in some situations, that they are set to linear (ie.
        dispcal -c). One way of determining when the VideoLUTs get used
        or not is to load a distinct calibration such as "strange.cal"
        provided in the <b>ref</b> folder, and check visually if it is
        affecting the video or not, ie. "dispcal strange.cal". Note that
        using MadVR 0.86.9 or latter in combination with a 3dLut with
        appended calibration curves will apply the calibration even with
        overlay plane rendering.<br>
      </li>
      <li>Do you want/need other applications to share the calibration
        curves or profile or not ? If you do, then it is desirable to
        choose a).</li>
      <li>Quality considerations. VideoLUTs may or may not be of greater
        depth than the standard 8 bit per color component frame buffer.
        If they are, and the video path passes that extra depth through
        to the display, and the display is capable of using that extra
        depth, then a) may be a desirable choice from a quality point of
        view. You can get some idea whether this is the case by running
        "dispcal -R". If the VideoLUT depth is not better than 8 bits,
        then it may be more desirable to choose b), since renders like
        MadVR can use dithering to give better than 8 bits precision in
        the video playback.<br>
      </li>
    </ul>
    <h5>4) Output device calibration and profiling.</h5>
    Output device profiling should basically follow the guide above in <a
      href="#PM1b">Adjusting and Calibrating a displays</a> and <a
      href="#PM1">Profiling Displays</a>. The assumption is that either
    you are calibrating/profiling your computer display for video, or
    your TV is connected to the computer you are creating
    calibrations/profiles on, and that the connection between the PC and
    TV display is such that full range RGB signals are being used, or
    that the Video card has automatically or manually been configured to
    scale full range RGB values to Video levels for the TV. If the
    latter is not possible, then use the -E options on dispcal and
    dispread. (See <b>Signal encoding</b> bellow for more details on
    this). It may also improve the accuracy of the display profile if
    you use the <a href="dispread.html#Z">dispread -Z</a> option to
    quantize the test values to the precision of the display
    system.&nbsp; Don't use the -E options on dispcal and dispread, nor
    the -Z option on dispread if you are using MadVR to display test
    patches using the "-d madvr" option.<br>
    <br>
    Once the profile has been created, it is possible to then use the
    resulting Device Link/3DLut with signal encoding other than full
    range or Video level RGB. <br>
    <h5>5) Target colorspace<br>
    </h5>
    In practical terms, there are five common Video and Digital Cinema
    encoding colorspaces. <br>
    <br>
    For Standard Definition:<br>
    <br>
    &nbsp;&nbsp;&nbsp; EBU 3213 or "PAL 576i" primaries.<br>
    <br>
    &nbsp;&nbsp;&nbsp; SMPTE RP 145 or "NTSC 480i" primaries.<br>
    <br>
    For High Definition:<br>
    <br>
    &nbsp;&nbsp;&nbsp; Rec 709 primaries.<br>
    <br>
    For Ultra High Defintion<br>
    <br>
    &nbsp;&nbsp;&nbsp; Rec 2020 primaries.<br>
    <br>
    For Digital Cinema<br>
    <br>
    &nbsp;&nbsp;&nbsp; SMPTE-431-2&nbsp; or "DCI-P3"<br>
    <br>
    PAL and NTSC have historically had poorly specified transfer curve
    encodings, and the Rec 709 HDTV encoding curve is the modern <a
      href="http://www.poynton.com/notes/DVAI/DVAI_TOC_full.html#23">recommendation</a>,
    but the overall interpretation of Video sources may in fact be
    partly determined by the expected standard Video display device
    characteristics (see <b>Viewing conditions adjustment and gamut
      mapping</b> below for more details).<br>
    <br>
    To enable targeting these colorspaces, ArgyllCMS provides 5 ICC
    profiles in the ref directory to use as source
    colorspaces:&nbsp;&nbsp;&nbsp; <br>
    <br>
    &nbsp;&nbsp;&nbsp; EBU3213_PAL.icm<br>
    <br>
    &nbsp;&nbsp;&nbsp; SMPTE_RP145_NTSC.icm<br>
    <br>
    &nbsp;&nbsp;&nbsp; Rec709.icm<br>
    <br>
    &nbsp;&nbsp;&nbsp; Rec2020.icm<br>
    <br>
    &nbsp;&nbsp;&nbsp; SMPTE431_P3.icm<br>
    <h5>6) Signal encoding</h5>
    Typical PC display output uses full range RGB signals (0 .. 255 in 8
    bit parlance), while typical Video encoding allows some head &amp;
    footroom for overshoot and sync of digitized analog signals, and
    typically uses a 16..235 range in 8 bits. In many cases Video is
    encoded as luma and color difference signals YCbCr (loosely known as
    YUV as well), and this also uses a restricted range 16..235 for Y,
    and 16..240 for Cb and Cr in 8 bit encoding. The extended gamut
    xvYCC encoding uses 16..235 for Y, and 1..254 for Cb and Cr.<br>
    <br>
    The signal encoding comes into play in two situations: 1)
    Calibrating and profiling the display, and 2) Using the resulting
    Device Link/3DLut.<br>
    The encoding may need to be different in these two situations,
    either because different video source devices are being used for
    calibration/profiling and for video playback, or because the video
    playback system uses the Device Link/3DLut at a point in its
    processing pipeline that requires a specific encoding.<br>
    <br>
    For calibration &amp; profiling, the display will be driven by a
    computer system so that dispcal and dispread can be used. By default
    these programs expect to output full range RGB signals, and it is
    assumed that either the display accepts full range signals, or that
    the graphics card or connection path has been setup to convert the
    full range values into Video range signals automatically or
    manually. If this is not the case, then both dispcal and dispread
    have a -E option that will modify them to output Video range RGB
    values.<br>
    <br>
    If MadVR is the target of the calibration and profiling, then there
    is an option to use it to display the calibration and profiling test
    patches (<b>-d madvr</b>). In this case, MadVR should be configured
    appropriately for full range or Video range encoding, and the -E
    flag should <u>not</u> be used with dispcal or dispread, since
    MadVR will be taking care of such conversions.<br>
    <br>
    If a calibration file was created using dispcal -E, then using it in
    dispread will automatically trigger Video level RGB signals during
    profiling. Any time such a Video level calibration is loaded into
    the Graphics card VideoLUTs using dispwin, or the calibration curve
    is converted to a 'vcgt' tag in a profile, the curve will also
    convert full range RGB to Video range RGB. This should be kept in
    mind so that if video playback is being performed with the
    calibration curves installed in the Graphics card VideoLUTs, that
    full range is converted only once to Video range (ie. In this
    situation MadVR output should be set to full range if being played
    back through the calibration curves in hardware, but only if dispcal
    -E has been used). On the other hand, if the calibration curves are
    incorporated into the DeviceLink/3dLUT, then the conversion to Video
    levels has to be done somewhere else in the pipeline, such as using
    MadVR video level output, or by the graphics card, etc.<br>
    <br>
    When creating the Device Link/3dLut, it is often necessary to
    specify one of the video encodings so that it fits in to the
    processing pipeline correctly. For instance the eeColor needs to
    have input and output encoding that suits the HDMI signals passing
    through it, typically Video Range RGB. MadVR needs Video Level RGB
    to match the values being passed through the 3dLut at that point.<br>
    <br>
    There are several version of YCbCr encoding supported as well, even
    though neither the eeColor nor the current version of MadVR need or
    can use them at present.<br>
    <h5>7) Black point mapping</h5>
    <p>Video encoding assumes that the black displayed on a device is a
      perfect black (zero light). No real device has a perfect black,
      and if a colorimetric intent is used then certain image values
      near black will get clipped to the display black point, loosing
      shadow detail. To avoid this, some sort of black point mapping is
      usually desirable. There are two mechanisms available in collink:
      a) Custom EOTF with input and/or output black point mapping, or b)
      using one of the smart gamut mapping intents that does black point
      mapping (e.g. la, p, pa, ms or s).<br>
    </p>
    <h5>8) Viewing conditions adjustment and gamut mapping</h5>
    <p> </p>
    <p>In historical TV systems, there is a viewing conditions
      adjustment being made between the bright studio conditions that TV
      is filmed in, and the typical dim viewing environment that people
      view it in. This is created by the difference between the encoding
      response curve gamma of about 2.0, and a typical CRT response
      curve gamma of 2.4. <br>
    </p>
    <p>In theory Rec709 defines the video encoding, but it seems in
      practice that much video material is adjusted to look as intended
      when displayed on a reference monitor having a display gamma of
      somewhere between 2.2 and 2.4, viewed in a dim viewing
      environment. The modern standard covering the display EOTF
      (Electro-Optical Transfer Curve) is <a
        href="http://www.itu.int/rec/R-REC-BT.1886-0-201103-I">BT.1886</a>,
      which defines a pure power 2.4 curve with an input offset and
      scale applied to account for the black point offset while
      retaining dark shadow tonality. So another means of making the
      viewing adjustment is to use the BT.1886-like EOTF for Rec709
      encoded material. Collink supports this using the <a
        href="collink.html#I">-I b</a>, and allows some control over the
      degree of viewing conditions adjustment by overriding the BT.1886
      gamma&nbsp; using the <a href="collink.html#Ib">-I b:g.g</a>
      parameter. This is the <b>recommended</b> approach to start with,
      since it gives good results with a single parameter.<br>
    </p>
    <p>The addition of a second optional parameter <a
        href="file:///D:/src/argyll/doc/collink.html#Ib">-I b:p.p:g.g</a>
      allows control over the degree of black point offset accounted for
      as an output offset, as opposed to input offset Once the effective
      gamma value has been chosen to suite the viewing conditions and
      set the overall contrast for mid greys, increasing the proportion
      of black offset accounted for in the output of the curve is a way
      of reducing the deep shadow detail, if it is being overly
      emphasized. </p>
    <p> An alternate approach to making this adjustment is to take
      advantage of the viewing conditions adjustment using the CIECAM02
      model available in collink. Some control over the degree of
      viewing conditions adjustment is possible by varying the viewing
      condition parameters. </p>
    <p>A third alternative is to combine the two approaches. The source
      is defined as Rec709 primaries with a BT.1886-like EOTF display in
      dim viewing conditions, and then CIECAM02 is used to adjust for
      the actual display viewing conditions. Once again, control over
      the degree of viewing conditions adjustment is possible by varying
      the viewing condition parameters<br>
    </p>
    <p><br>
    </p>
    <p><b>9) Correcting for any black point inaccuracy in the display
        profile</b><br>
    </p>
    <p>Some video display devices have particularly good black points,
      and any slight raising of the black due to innacuracies in the
      display profile near black can be objectionable. As well as using
      the <a href="targen.html#V">targen -V flag</a> to improve
      accuracy near black during profiling, if the display is known to
      be well behaved (ie. that it's darkest black is actually at RGB
      value 0,0,0), then the <a href="collink.html#b">collink -b</a>
      flag can be used, to force the source RGB 0,0,0 to map to the
      display 0,0,0.<br>
    </p>
    <h5>Putting it all together:</h5>
    In this example we choose to create a display calibration first
    using dispcal, and create a simple matrix profile as well:<br>
    <br>
    &nbsp; <tt>dispcal -v -o -qm -k0 -w 0.3127,0.3290 -gs -o TVmtx.icm
      TV</tt><br>
    <br>
    We are targeting a D65 white point (<tt>-w 0.3127,0.3290)</tt> and
    an sRGB response curve.<br>
    <br>
    If you are using the madTPG you would use:<br>
    <br>
    &nbsp; <tt>dispcal -v -d madvr -o -qm -k0 -w 0.3127,0.3290 -gs -o
      TVmtx.icm TV</tt><br>
    <br>
    Then we need to create a display patch test set. We can use the
    simple matrix to pre-condition the test patches, as this helps
    distribute them where they will be of most benefit. If have
    previously profiled your display, you should use that previous
    profile, or if you decided not to do a dispcal, then the Rec709.icm
    should be used as a substitute. Some per channel and a moderate
    number of full spread patches is used here - more will increase
    profiling accuracy, a smaller number will speed it up. Since the
    video or film material is typically viewed in a darkened viewing
    environment, and often uses a range of maximum brightnesses in
    different scenes, the device behavior in the dark regions of its
    response are often of great importance, and using the <a
      href="targen.html#V">targen -V</a> parameter can help improve the
    accuracy in this region at the expense of slightly lower accuracy in
    lighter regions.<br>
    <br>
    &nbsp; <tt>targen -v -d3 -s30 -g100 -f1000 -cTVmtx.icm -V1.8 TV</tt><br>
    <br>
    The display can then be measured:<br>
    <br>
    &nbsp; <tt>dispread -v -k -Z8 TV.cal TV</tt><br>
    <br>
    or using madTPG:<br>
    <br>
    &nbsp;dispread -v -d madvr -K TV.cal TV<br>
    <br>
    and then a cLUT type ICC profile created. Since we will be using
    collink smart linking, we minimize the B2A table size. We use the
    default colprof -V parameter carried through from targen:<br>
    <br>
    &nbsp; <tt>colprof -v -qh -bl TV</tt><br>
    <br>
    Make sure you check the delta E report at the end of the profile
    creation, to see if the sample data and profile is behaving
    reasonably. Depending on the type of device, and the consistency of
    the readings, average errors of 5 or less, and maximum errors of 15
    or less would normally be expected. If errors are grossly higher
    than this, then this is an indication that something is seriously
    wrong with the device measurement, or profile creation.<br>
    <br>
    If you would like to use the display ICC profile for general color
    managed applications, then you would compute a more complete
    profile:<br>
    <br>
    &nbsp; <tt>colprof -v -qh TV</tt><br>
    <br>
    The recommended approach then is to create a Device Link that uses a
    BT.1886 black point and viewing conditions adjustment, say one of
    the following:<br>
    <br>
    <tt>&nbsp; collink -v -Ib:2.4 -b -G -ir Rec709.icm TV.icm
      HD.icm&nbsp;&nbsp; # dark conditions</tt><tt><br>
    </tt><tt> &nbsp; collink -v -Ib&nbsp;&nbsp;&nbsp;&nbsp; -b -G -ir
      Rec709.icm TV.icm HD.icm&nbsp;&nbsp; # dim conditions - good
      default</tt><tt><br>
    </tt><tt> &nbsp; collink -v -Ib:2.1 -b -G -ir Rec709.icm TV.icm
      HD.icm&nbsp;&nbsp; # mid to dim conditions</tt><tt><br>
    </tt><tt> &nbsp; collink -v -Ib:2.0 -b -G -ir Rec709.icm TV.icm
      HD.icm&nbsp;&nbsp; # mid to light conditions</tt><br>
    <br>
    or you could do it using pure CIECAM02 adjustment and a black point
    mapping:<br>
    <br>
    <tt>&nbsp; collink -v -ctv -dmd -da:1 -G -ila Rec709.icm TV.icm
      HD.icm&nbsp; # very dark conditions</tt><tt><br>
    </tt><tt> &nbsp; collink -v -ctv -dmd -da:3 -G -ila Rec709.icm
      TV.icm HD.icm&nbsp; # dim conditions</tt><tt><br>
    </tt><tt> &nbsp; collink -v -ctv -dmd -da:7 -G -ila Rec709.icm
      TV.icm HD.icm&nbsp; # mid to dim conditions - good default</tt><tt><br>
    </tt><tt> &nbsp; collink -v -ctv -dmd -da:15 -G -ila Rec709.icm
      TV.icm HD.icm # mid conditions</tt><br>
    <br>
    or using both to model a reference video display system that is
    adapted to your viewing conditions:<br>
    <tt><br>
    </tt><tt> &nbsp; collink -v -Ib -c md -dmd -da:5&nbsp; -G -ila
      Rec709.icm TV.icm HD.icm # very dark conditions</tt><tt><br>
    </tt><tt> &nbsp; collink -v -Ib -c md -dmd -da:10 -G -ila Rec709.icm
      TV.icm HD.icm&nbsp; # dim conditions</tt><tt><br>
    </tt><tt> &nbsp; collink -v -Ib -c md -dmd -da:18 -G -ila Rec709.icm
      TV.icm HD.icm&nbsp; # mid to dark conditions</tt><tt><br>
    </tt><tt> &nbsp; collink -v -Ib -c md -dmd -da:30 -G -ila Rec709.icm
      TV.icm HD.icm&nbsp;&nbsp; # mid to dark conditions</tt><br>
    <br>
    None of the above examples incorporate the calibration curves, so it
    is assumed that the calibration curves would be installed so that
    the Video Card applies calibration, ie:<br>
    <br>
    &nbsp;&nbsp;&nbsp; <tt>dispwin TV.cal</tt><br>
    <br>
    or the simple matrix profile installed:<br>
    <br>
    &nbsp;&nbsp;&nbsp; <tt>dispwin -I TVmtx.icm</tt><br>
    <br>
    or a the more complete display profile could be installed:<br>
    <br>
    &nbsp; dispwin -I TV.icm<br>
    <br>
    See also <a href="dispprofloc.html">here</a> for information on how
    to make sure the calibration is loaded on each system start. If not,
    then you will want to incorporate the calibration in the Device
    Link/3dlut by using collink "-a TV.cal".<br>
    <br>
    If the video path needs Video Level RGB encoding but does not
    provide a means to do this, then you will want to include the <b>-E</b>
    flag in the dispcal and dispread command lines above.<br>
    <br>
    Below are specific recommendation for the eeColor and MadVR that
    include the flags to create the .3dlut and encode the input and
    output values appropriately, but only illustrate using the
    recommended BT.1886 black point and viewing conditions adjustments,
    rather than illustrating CIECAM02 etc. use.<br>
    <br>
    For faster exploration of different collink option, you could omit
    the "colprof -bl" option, and use collink "-g" instead of "-G",
    since this<br>
    will greatly speed up collink. Once you are happy with the link
    details, you can then generate a higher quality link/3dLut using
    "collink -G ..".<br>
    <br>
    You can also increase the precision of the device profile by
    increasing the number of test patches measured (ie. up to a few
    thousand, depending on how long you are prepared to wait for the
    measurement to complete, and how stable your display and instrument
    are).<br>
    <br>
    Alternatives to relative colorimetric rendering ("-i r") or
    luminance matched appearance ("-i la") used in the examples above
    and below, are, perceptual ("-i p") which will ensure that the
    source gamut is compressed rather than clipped by the display, or
    even a saturation rendering ("-i ms"), which will expand the gamut
    of the source to the full range of the output.<br>
    <br>
    <br>
    <b>eeColor</b><br>
    <br>
    For PC use, where the encoding is full range RGB:<br>
    <br>
    &nbsp; <tt>collink -v -3e -Ib -b -G -ir -a TV.cal Rec709.icm TV.icm
      HD.icm </tt><br>
    <br>
    For correct operation both the 3DLut HD.txt and the per channel
    input curves HD-first1dred.txt, HD-first1dgreen.txt and
    HD-first1dblue.txt. the latter by copying them over the default
    input curve files uploaded by the TruVue application.<br>
    <br>
    See <a
      href="http://www.avsforum.com/t/1464890/eecolor-processor-argyllcms">&lt;http://www.avsforum.com/t/1464890/eecolor-processor-argyllcms&gt;</a>
    for some more details.<br>
    <br>
    Where the eeColor is connected from a Video source using HDMI, it
    will probably be processing TV RGB levels, or YCbCr encoded signals
    that it converts to/from RGB internally, so<br>
    <br>
    &nbsp; <tt>collink -v -3e -et -Et -Ib -b -G -ir -a TV.cal
      Rec709.icm TV.icm HD.icm </tt><br>
    <br>
    in this case just the HD.txt file needs installing on the eeColor,
    but make sure that the original linear "first1*.txt files are
    re-installed, or install the ones generated by collink, which will
    be linear for -e t mode.<br>
    <br>
    <b>MadVR</b><br>
    <br>
    MadVR 0.86.9 or latter has a number of features to support accurate
    profiling and calibration, and is the recommended version to
    use.&nbsp; It converts from the media colorspace to the 3dLut input
    space automatically with the type of source being played, but has
    configuration for to 5 3dLuts, each one optimized for a particular
    source color space. The advantage of building and installing several
    3dLuts is that unnecessary gamut clipping can be avoided.<br>
    <br>
    If you are just building one 3dLut then Rec709 source is a good one
    to pick.<br>
    <br>
    If you want to share the VideoLUT calibration curves between your
    normal desktop and MadVR, then it is recommended that you install
    the display ICC profile and use the -H option:<br>
    <br>
    <tt>&nbsp;&nbsp;&nbsp; collink -v -3m -et -Et -Ib -b -G -ir -H
      TV.cal Rec709.icm TV.icm HD.icm</tt><tt><br>
    </tt><tt> </tt><tt><br>
    </tt><tt> &nbsp;&nbsp;&nbsp; collink -v -3m -et -Et -Ib -b -G -ir </tt><tt><tt>-H























        TV.cal </tt>EBU3213_PAL.icm TV.icm SD_PAL.icm</tt><tt><br>
    </tt><tt> </tt><tt><br>
    </tt><tt> &nbsp;&nbsp;&nbsp; collink -v -3m -et -Et -Ib -b -G -ir </tt><tt><tt>-H























        TV.cal </tt>SMPTE_RP145_NTSC.icm TV.icm SD_NTSC.icm</tt><br>
    <br>
    For best quality it is better to let MadVR apply the calibration
    curves using dithering, and allow it to set the graphics card to
    linear by using the -a option:<br>
    <br>
    <tt>&nbsp;&nbsp;&nbsp; collink -v -3m -et -Et -Ib -b -G -ir -a
      TV.cal Rec709.icm TV.icm HD.icm</tt><tt><br>
    </tt><tt> </tt><tt><br>
    </tt><tt> &nbsp;&nbsp;&nbsp; collink -v -3m -et -Et -Ib -b -G -ir </tt><tt><tt>-a























        TV.cal </tt>EBU3213_PAL.icm TV.icm SD_PAL.icm</tt><tt><br>
    </tt><tt> </tt><tt><br>
    </tt><tt> &nbsp;&nbsp;&nbsp; collink -v -3m -et -Et -Ib -b -G -ir </tt><tt><tt>-a























        TV.cal </tt>SMPTE_RP145_NTSC.icm TV.icm SD_NTSC.icm</tt><br>
    <br>
    the consequence though is that the appearance of other application
    will shift when MadVR is using the 3dLut and loading the calibration
    curves.<br>
    <br>
    The 3dLut can be used by opening the MadVR settings dialog,
    selecting "calibration" and then selecting "calibrate this display
    by using an external 3DLUT file", and then using the file dialog to
    use it.<br>
    <br>
    If neither the -a no -H options are used, then no calibration curves
    will be appended to the 3dLut, and MadVR will not change the
    VideoLUTs when that 3dLut is in use. It is then up to you to manage
    the graphics card VideoLUTs in some other fashion.<tt><br>
      <br>
    </tt>
    <hr size="2" width="100%"><br>
    <h3><a name="TV2"></a>Verifying Video Calibration</h3>
    <p>Often it is desirable to verify the results of a video
      calibration and profile, and the following gives an outline of how
      to use ArgyllCMS tools to do this. It is only possible to expect
      perfect verification if a colorimetric intent was used during
      linking - currently it's not possible to exactly verify a
      perceptual or CIECAM02 viewing condition adjusted link.<br>
      <br>
    </p>
    <p>The first step is to create a set of test points. This is
      essentially the same as creating a set of test points for the
      purposes of profiling, although it is best not to create exactly
      the same set, so as to explore the colorspace at different
      locatioins. For the purposes here, we'll actually create a regular
      grid test set, since this makes it easier to visualize the
      results, although a less regular set would probably be better for
      numerical evaluation:<br>
    </p>
    <p>&nbsp; targen -v -d3 -e1 -m6 -f0 -W verify<br>
    </p>
    <p>We make sure there is at least one white patch usin g -e1, a 20%
      increment grid using -m6, no full spread patches, and create an
      X3DOM 3d visualization of the point set using the -W flag. It is
      good to take a look at the verifyd.x3d.html file using a Web
      browser. You may want to create several test sets that look at
      particular aspects, ie. neutral axis response, pure colorant
      responses, etc.<br>
    </p>
    <p>Next we create a reference file by simulating the expected
      response of the perfect video display system. Assuming the collink
      options were "-et -Et -Ib -G -ir Rec709.icm TV.icm HD.icm" then we
      would:<tt><tt><br>
        </tt></tt></p>
    <p><tt><tt>&nbsp; copy verify.ti1 ref.ti1<br>
          &nbsp; fakeread -v -b -Z8 TV.icm Rec709.icm ref<br>
        </tt></tt></p>
    <p>You should adjust the parameters as necessary, so that the
      reference matches the link options. For instance, if your link
      options included "-I b:0.2:2.15" then the equivalent fakeread
      option "-b 0.2:2.15:TV.icm" should be used, etc.<br>
    </p>
    <hr size="2" width="20%">
    <p>A sanity check we can make at this point is to see what the
      expected result of the profiling &amp; calibration will be, by
      simulating the reproduction of this test set:<br>
    </p>
    <p><tt>&nbsp; copy verify.ti1 checkA.ti1</tt><tt><br>
        &nbsp; fakeread -v -et -Z8 -p HD.icm -Et TV.icm checkA<br>
      </tt></p>
    <p>If you used collink -a, then the calibration incorporated in the
      device link needs to be undone to match what the display profile
      expects:</p>
    <p><tt>&nbsp; fakeread -v -et -Z8 -p HD.icm -Et -K TV.cal TV.icm
        checkA</tt></p>
    <p><tt>and then you can verify:<br>
      </tt></p>
    <p><tt>&nbsp; colverify -v -n -w -x ref.ti3 checkA.ti3<br>
      </tt></p>
    <p>If you have targeted some other white point rather than video D65
      for the display, then use the -N flag instead of -n to align the
      white points. [ Note that there can be some small discrepancies in
      this case in some parts of the color space if a CIECAM02 linking
      intent was used, due to the slightly different chromatic
      adaptation algorithm it uses compared to the one used by verify to
      match the white points.]<tt><br>
      </tt></p>
    <p><tt>&nbsp; v</tt><tt>erify -v -N -w -x ref.ti3 checkA.ti3</tt><br>
    </p>
    <p>This will give a numerical report of the delta E's, and also
      generate an X3DOM plot of the errors in L*a*b* space. The
      important thing is to take a look at the checkA.x3d.html file, to
      see if gamut clipping is occurring - this is the case if the large
      error vectors are on the sides or top of the gamut. Note that the
      perfect cube device space values become a rather distorted cube
      like shape in the perceptual L*a*b* space. If the vectors are
      small in the bulk of the space, then this indicates that the link
      is likely to be doing the right thing in making the display
      emulate the video colorspace with a BT.1886 like black point
      adjustment. You could also check just the in gamut test points
      using:<br>
    </p>
    <p><tt>&nbsp; v</tt><tt>erify -v -N -w -x -L TV.icm ref.ti3
        checkA.ti3<br>
        <br>
      </tt></p>
    <hr size="2" width="20%">
    <p>You can explicitly compare the gamuts of your video space and
      your display using the gamut tools:<br>
    </p>
    <p><tt>&nbsp; iccgamut -ff -ia Rec709</tt><tt><br>
      </tt><tt> &nbsp; iccgamut -ff -ia TV.icm</tt><tt><br>
      </tt><tt> &nbsp; viewgam -i Rec709.gam TV.gam gamuts</tt><br>
    </p>
    <p>and look at the gamuts.x3d.html file, as well as taking notice of
      % of the video volume that the display intersects. The X3DOM solid
      volume will be the video gamut, while the wire frame is the
      display gamut. If you are not targetting D65 with your display,
      you should use iccgamut <b>-ir</b> instead of <b>-ia</b>, so as
      to align the white points.<br>
    </p>
    <hr size="2" width="20%">
    <p>The main verification check is to actually measure the display
      response and compare it against the reference. Make sure the
      display is setup as you would for video playback and then use
      dispread:<br>
    </p>
    <p><tt>&nbsp; copy verify.ti1 checkB.ti1</tt><tt><br>
      </tt><tt> &nbsp; dispread -v -Z8 checkB</tt><br>
    </p>
    <p>You would add any other options needed (such as <b>-y</b> etc.)
      to set your instrument up properly. If you are using madTPG, then
      configure madVR to use the 3dLut you want to measure as the
      default, and also use the dispread -V flag to make sure that the
      3dLut is being used for the measurements: [<b>Note</b> that if the
      version of MadVR you are using does not have radio buttons in its
      calibration setup to indicate a default 3dLut, then the 3dLut
      under test should be the only one set - all others should be
      blank. ]<br>
    </p>
    <p><tt>&nbsp; dispread -v -d madvr -V checkB</tt><br>
    </p>
    <p>Verify the same way as above:<br>
    </p>
    <p><tt>&nbsp; v</tt><tt>erify -v -n -w -x ref.ti3 checkB.ti3<br>
      </tt></p>
    <p>If your display does not cover the full gamut of your video
      source, the errors are probably dominated by out of gamut colors.
      You can verify just the in gamut test values by asking verify to
      skip them, and this will give a better notion of the actual device
      link and calibration accuracy:<tt><br>
      </tt></p>
    <p><tt>&nbsp; v</tt><tt>erify -v -n -w -x -L TV.icm ref.ti3
        checkB.ti3</tt></p>
    <p><br>
    </p>
    <p>&nbsp;<br>
    </p>
    <p><br>
      <br>
    </p>
    <br>
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generated by cgit v1.2.3 (git 2.25.1) at 2024-11-18 11:41:10 +0000