<!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 auto calibration of instrument</span></font><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>The <b>-N</b> option disables the automatic calibration of an instrument if it is possible to do so. Sometimes it is awkward to have to re-calibrate and instrument every time a tool starts, and unnecessary if the instrument has recently been calibration, and this switch prevents it happening.<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>
