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diff --git a/doc/Scenarios.html b/doc/Scenarios.html new file mode 100644 index 0000000..3995d21 --- /dev/null +++ b/doc/Scenarios.html @@ -0,0 +1,2177 @@ +<!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=ISO-8859-1"> + </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> <a href="#PM1a">Checking you can access your + display<br> + </a></h4> + <h4> <a href="#PM1b">Adjusting and Calibrating a + displays</a></h4> + <h4> <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> <a href="#PM2">Creating display test values</a></h4> + <h4> <a href="#PM3">Taking readings from a + display</a></h4> + <h4> <a href="#PM4">Creating a display profile</a></h4> + <h4> <span style="text-decoration: underline;"></span><a + href="#PM5">Installing a display profile</a></h4> + <h4> <span style="text-decoration: underline;"></span><a + href="#PM6">Expert tips when measuring displays</a></h4> + <h4> <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> <a href="#PS2">Types of test charts</a></h4> + <h4> <a href="#PS3">Taking readings from a + scanner</a></h4> + <h4> <a href="#PS4">Creating a scanner profile</a></h4> + <h4><br> + <a href="#PP1">Profiling Printers</a></h4> + <h4> <a href="#PP2">Creating a print profile + test chart</a></h4> + <h4> <a href="Scenarios.html#PP2b">Printing a + print profile test chart</a></h4> + <h4> <a href="#PP3">Reading a print test chart + using an instrument</a></h4> + <h4> <a href="#PP4">Reading a print test chart + using a scanner</a></h4> + <h4> </h4> + <h4> <a href="#PP5">Creating a printer profile<br> + </a></h4> + <h4> <a href="#PP6">Choosing a black generation + curve</a></h4> + <br> + <h4><a href="Scenarios.html#PC1">Calibrating Printers</a></h4> + <h4> <a href="Scenarios.html#PC2">Calibrated + print workflows</a></h4> + <h4> <a href="Scenarios.html#PC3">Creating a + print calibration test chart</a></h4> + <h4> </h4> + <h4> <a href="Scenarios.html#PC4">Creating a + printer calibration<br> + </a></h4> + <h4> <a href="Scenarios.html#PC5">Using a printer + calibration</a></h4> + <h4> <a href="#PC6">How profile ink limits are + handled when calibration is being used<br> + </a></h4> + <h4><br> + <a href="#LP1">Linking Profiles</a></h4> + <h4><br> + <a href="#TR1">Transforming colorspaces of raster files</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. + Adjustment and calibration are prior steps to profiling, in which + the display is adjusted using it's screen controls, and then + per channel lookup tables are created to make it meet a well behaved + response of the desired type. The 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 + 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, 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, 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, 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> + <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> + <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 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 <span style="font-weight: bold;">Microsoft Color Control Panel Applet for Windows XP</span> + available for download from Microsoft to do this, but <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->Programs->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> + + + + + + + + + (<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, (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> 1) Don't attempt to calibrate, just profile the display.<br> + 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> 2a) Use dispcal to create a calibration and a quick profile + that incorporates the calibration into the profile.<br> + 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> + 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> + <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> + <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.christophe-metairie-photographie.com/eng%20digital%20target.html">Christophe + + + + + + + + + Métairie's Digital TargeT 003</a> and <a +href="http://www.christophe-metairie-photographie.com/eng%20digital%20target.html">Christophe + + + + + + + + + Métairie's Digital Target - 3</a> :<br> + <br> + <img alt="CMP_DT_003" src="CMP_DT_003.jpg" style="width: 186px; + height: 141px;"> <img style="width: 203px; height: 140px;" + alt="CMP_Digital_Target-3" src="CMP_Digital_Target-3.jpg"><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>: <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"> + <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 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 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> + <a href="chartread.html">chartread</a> -n -a + 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.<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> + <a href="txt2ti3.html">txt2ti3</a> + ColorCheckerSG.txt ColorCheckerSG<br> + <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, making use of the chart reference file <span + style="font-weight: bold;">ref/i1_RGB_Scan_1.4.ti2</span>:<br> + <a href="chartread.html">chartread</a> -n -a + 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-3 chart with + 570 patches, the <span style="font-weight: bold;">ref/CMP_Digital_Target-3.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 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), 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 profile is behaving reasonably.<br> + <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 + 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 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 & 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> + <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> + <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 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> + <a href="targen.html#d">-d2</a> <a href="targen.html#f">-f1053</a> + <a href="targen.html#c">-c OldPrinterA</a> <a + href="targen.html#p1">PrinterA</a><br> + <br> + <a href="targen.html">targen</a> <a href="targen.html#v">-v</a> + <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> + <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> + 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.). 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 & B), while + a reflective print, will have subtractive primaries (C, M, Y & + 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). 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> + <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 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 (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 how the minimum black is zero up to 93% of the + white->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->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 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. + + <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> + <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> + <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 <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> + <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> + <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> + <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> + <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> + <a href="printtarg.html#K">printtarg</a> +To +apply +calibration +to +a +profile +test +chart, + + + + + + + + + and/or to have it included in .ti3 file.<br> + <a href="cctiff.html#p2">cctiff</a> +To +apply +color +management +and +calibration +to +an + + + + + + + + + image file.<br> + <a href="applycal.html#p1">applycal</a> + + + + + + + + + To incorporate calibration into an ICC profile.<br> + <a href="chartread.html#I">chartread</a> +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> + <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> + <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> + <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> + <a href="cctiff.html">cctiff</a> <a + href="cctiff.html#p1">Source2Destination.icm</a> <a + href="cctiff.html#p2">PrinterA_c.cal</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#p2">PrinterA_c.cal</a> <a href="cctiff.html#p3">infile.jpg</a> + <a href="cctiff.html#p4">outfile.jpg</a><br> + <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> + <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> + <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="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> <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> + + <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> <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> <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> + <br> + <br> + <br> + <br> + <br> + <br> + <br> + <br> + <br> + <br> + <br> + <br> + <br> + <br> + <br> + <br> + <br> + <br> + </body> +</html> |