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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>illumread</title>
<meta http-equiv="content-type" content="text/html;
charset=ISO-8859-1">
<meta name="author" content="Graeme Gill">
</head>
<body>
<h2><b>spectro/illumread</b></h2>
<h3>Summary</h3>
Use an instrument or instruments to measure an illuminant spectrum,
including estimate
its Ultra Violet content. A combination of direct illumination
readings
and readings from a piece of paper having some FWA content are used
for
this. (If the UV content is not needed, or a suitable instrument is
not
available, then <a href="spotread.html">spotread</a> should be used
instead.)<br>
<h3>Usage Summary</h3>
<small><span style="font-family: monospace;">illumread [-options]
illuminant.sp</span><br style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#v">-v</a><span
style="font-family: monospace;">
Verbose mode</span><span style="font-family:
monospace;"></span></small><small><span style="font-family:
monospace;"></span></small><br style="font-family: monospace;">
<small><span style="font-family: monospace;"></span><span
style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#S">-S</a><span
style="font-family: monospace;">
Plot
the readings in a graph window.</span><br style="font-family:
monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#c">-c comport</a><span
style="font-family: monospace;">
Set
COM port, 1..4
(default 1)</span><span style="font-family: monospace;"></span><span
style="font-family: monospace;"></span><span style="font-family:
monospace;"></span></small><small><span style="font-family:
monospace;"></span></small><font size="-1"><span
style="font-family: monospace;"></span></font><font size="-1"><span
style="font-family: monospace;"><br>
</span></font><font size="-1"><span style="font-family:
monospace;"> <a href="#N">-N</a>
Disable
initial calibration of instrument</span></font> if possible<br>
<font size="-1"><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#H">-H</a><span
style="font-family: monospace;">
Use high resolution spectrum mode (if
available)<br>
</span></font><font size="-1"><span style="font-family:
monospace;"> <a href="#W">-W n|h|x</a>
Override
serial port flow control: n = none, h = HW, x = Xon/Xoff</span></font><br>
<small><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#D">-D [level]</a><span
style="font-family: monospace;">
Print
debug diagnostics to stderr</span></small><br>
<font size="-1"><span style="font-family: monospace;"><a
href="#file"><span style="font-style: italic;">illuminant.sp</span></a>
File
to save measurement to<br style="font-family: monospace;">
</span></font><small><span style="font-family: monospace;"></span><span
style="font-family: monospace;"></span></small><br>
<h3>Usage Details and Discussion</h3>
<b>illumread</b> uses a suitable instrument to read an illuminant
spectrum, and uses an indirect method to estimate the Ultra Violet
content of the illuminant, so as to provide better accuracy with <a
href="FWA.html">FWA
compensation</a>. An instrument or combination of instruments
capable
of spectral measurement of both
emissive measurement and reflective measurement without a U.V.
filter
is required for this.<br>
<br>
<a name="v"></a>The <b>-v</b> flag causes extra information to be
printed out during
chartread operation.<br>
<br>
<a name="S"></a>The <b>-S</b> flag enables the plotting of the
spectral
reflectance/transmittance values. You must select the plot window
and
strike a key
in it to continue with another measurement.<br>
<br>
<a name="c"></a> The instrument is assumed to communicate through a
USB or serial communication port, and the initial port can be
selected
with the
<b>-c</b>
option,
if the instrument is not connected to the first port. If you invoke
<span style="font-weight: bold;">illumread</span>
so as to display the usage
information (i.e. "illumread -?" or "illumread --"), then the
discovered
USB and serial ports will be listed. On
UNIX/Linux, a list of all possible serial ports are shown, but not
all
of them may
actually be present on your system.<br>
<br>
<a name="N"></a><span style="font-weight: bold;">-N</span> Any
instrument that requires regular calibration will ask for
calibration on initial start-up. Sometimes this can be awkward if
the instrument is being mounted in some sort of measuring jig, or
annoying if several sets of readings are being taken in quick
succession. The -<span style="font-weight: bold;">N</span>
suppresses this initial calibration if a valid and not timed out
previous calibration is recorded in the instrument or on the host
computer. It is advisable to only use this option on the second and
subsequent measurements in a single session.<br>
<br>
<a name="H"></a> The -<span style="font-weight: bold;">H</span>
option
turns on high resolution spectral mode, if the instrument supports
it.
See <a href="instruments.html">Operation of particular instruments</a>
for more details.<br>
<br>
<a name="W"></a>The <b>-W</b> <span style="font-weight: bold;">n|h|x</span>
parameter overrides the default serial communications
flow control setting. The value <span style="font-weight: bold;">n</span>
turns all flow control off, <span style="font-weight: bold;">h</span>
sets hardware handshaking, and <span style="font-weight: bold;">x</span>
sets Xon/Xoff handshaking. This commend may be useful in workaround
serial communications issues with some systems and cables. <br>
<br>
<a name="D"></a>The <b>-D</b> flag causes communications
and other instrument diagnostics to be printed to stdout. A level
can
be set between 1 .. 9, that may give progressively more verbose
information, depending on the instrument. This can be useful in
tracking
down why an instrument can't connect.<br>
<br>
<a name="file"></a>The <span style="font-weight: bold; font-style:
italic;">illuminant.sp</span> is
the name of the file to save the resulting illuminant spectrum to.
The
format used is <a href="File_Formats.html#.sp">.sp</a>.<br>
<br>
<hr style="width: 100%; height: 2px;"><br>
Unlike the other measurement utilities, <span style="font-weight:
bold;">illumread</span> doesn't connect to the
instrument until it is about to make a measurement. This allows for
the
possibility of using a different instrument for each measurement.<br>
<br>
It will display a menu:<br>
<br>
Press 1 .. 6<br>
1) Measure direct illuminant<br>
2) Measure illuminant reflected from paper<br>
3) Measure paper<br>
4) Select another instrument, Currently 1 'usb:/bus4/dev2/
(GretagMacbeth i1 Pro)'<br>
5) Compute illuminant spectrum, average result with 0 previous
readings
& save it<br>
6) Compute illuminant spectrum from this reading & save result<br>
7) Exit<br>
<br>
There are three measurements to be made, after which the illuminant
can
be computed and saved. Before each measurement, the instrument may
need
calibrating.<br>
<br>
The first measurement needs a spectral instrument capable of reading
in
an ambient or emissive mode. For instance, a Spectrolino, Eye-One
Pro
or ColorMunki would be suitable instruments.<br>
<br>
The second measurement needs a spectral instrument capable of
reading
in an projector or emissive mode. For instance, a Spectrolino,
Eye-One
Pro or ColorMunki would be suitable instruments.<br>
<br>
The third measurement needs a spectral instrument capable of reading
in
reflective mode with UV included. For instance, a Spectrolino,
Eye-One
Pro, DTP20, DTP22 or DTP41 would be suitable instruments, as
long
as they are not fitted with UV filters.<br>
<br>
To be able to estimate the level of Ultra Violet (UV) light in the
illuminant, a reasonable sized piece of white paper needs to be
used.
The paper should have some noticeable level of FWA (Fluorescent
Whitener Additive, or Optical Brightening Agents) in it, so that it
responds to UV light. A piece of cheap copier paper is ideal, since
cheap paper is typically whitened with large amounts of FWA. If the
paper is thin (less than 160 gsm) then two or three sheets should be
used to prevent any background showing through. [If the intention is
to
use the illuminant spectrum for proofing to a particular paper, then
an
alternative might be to use a piece of the intended paper for this
purpose. It's unclear which may give a better result.]<br>
<br>
The first measurement <span style="font-weight: bold;">1)</span>,
is
to use either the ambient or emissive measurement mode to measure
the
illumination directly.<br>
<br>
<div style="margin-left: 40px;">If the instrument supports an
ambient
measurement capability, then it will be used. If the insrument
does not
have an ambient mode, then an emissive measurement mode can be
used,
although typically many illuminants are too bright to directly
point
the instrument at. A work-around is to reflect the illuminant from
a
spectrally flat white surface. A good candidate for this is a
piece of
white, fine textured polystyrene foam. [The suitability of a
reflector
can be checked using <span style="font-weight: bold;">spotread -S</span>
to check that the reflection characteristic is close to flat.]<br>
<br>
<img style="width: 228px; height: 300px;" alt="Measuring Ambient"
src="illumread_1.jpg"><img style="width: 141px; height: 282px;"
alt="Measuring Ambient" src="illumread_2.jpg"> <img
style="width: 226px; height: 282px;" alt="Measuring Ambient"
src="illumread_3.jpg"><br>
</div>
<br>
The second measurement <span style="font-weight: bold;">2)</span>,
is
to measure the illuminant after it has reflected from the paper.<br>
<br>
<div style="margin-left: 40px;">This is done by placing the paper
such
that it is uniformly illuminated with reasonable brightness, and
then
placing the instrument so that it receives the reflected light
from the
paper. This is typically achieved by placing the instrument close
to
the paper at about 45º, so that it's aperture has a clear
view of
the illuminated paper, but avoiding shadowing the region that is
in
view. <br>
<br>
<img style="width: 219px; height: 261px;" alt="Measuring via
Paper" src="illumread_5.jpg"><img style="width: 252px; height:
259px;" alt="Measuring via Paper" src="illumread_4.jpg"><br>
</div>
<br>
The third measurement <span style="font-weight: bold;">3)</span>,
is
to measure the paper directly using the instrument reflective mode
measurement.<br>
<div style="margin-left: 40px;"><img style="width: 186px; height:
162px;" alt="Measuring Paper" src="illumread_6.jpg"><br>
</div>
If a different instrument is needed, use <span style="font-weight:
bold;">4)</span> to select from the available
instruments attached to your computer.<br>
<br>
Once these three measurements have been made, then the illuminant
readings spectrum
can be computed and save using <span style="font-weight: bold;">6)</span>,
or a series of readings can be made with each reading being averages
with the previous readings before saving it by using <span
style="font-weight: bold;">5)</span>. Note that the averaged
readings
will be weighted by their absolute intensities, and that while the
direct and indirect illumination needs measuring for each reading,
the
same paper measurement can be used each time.<br>
<br>
If plotting is enabled, a plot of the
measured (black) and with estimated UV (red) is plotted. This is
followed by a plot showing measured paper reflectance (black) and
the
FWA calculated paper reflectance (red).<br>
<br>
<br>
Illumread can then be terminated using <span style="font-weight:
bold;">7)</span>.<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
</body>
</html>
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