What I would like to measure or get a spectral plot for is the light of the Eye 1 Basic, UV enabled version. The RAW measurement, not the tweaked measurement that my Eye 1 delivers when I put it on for example Spectralon that gives a near 100% reflectance on all wave lengths. I don't think that information is available outside X-Rite premises.
You can get the raw readings by using Argyll's "high resolution" mode. This provides the raw measurements at 3.3nm intervals rather than the massaged 10nm data.
We use the following methodology for tracking shifts in our fleet of spectrophotometers. It may not be perfect, and it does not give absolute accuracy values, but it certainly allows diagnosing when a particular instrument is out of calibration. For background, we have half a dozen Spectrolino/Spectroscans, 4 iCColors, and i1iSis automated readers. The other spectros (i1, DTP24, etc.) are not used often enough to worry about. It became readily apparent that we needed a method of tracking instrument drift and when servicing was required.
Our first approach was to use sets of plastic tiles. A visit to a big-box home supply store with a DTP24 in hand revealed several neutral solid-surface counter top materials that had reasonably flat spectral response curves. None were available in bulk, but the manufacturers were happy to supply samples. We measured these on the Spectrolinos and then measured small test charts formatted for the iCColor scanners printed on OBA-free paper. The plastic tiles had minimal temperature color shift (within Spectrolino measurement noise) over a +/-2C range. The small charts were reprinted regularly at a local Silver-Halide lab, and we compared Spectroscan readings vs. iCColor for those. The normal failure modes, in order of occurrence frequency, were: instrument Calibration reference being dirty, Spectrolino measurement filter collecting dust, and the measurement lamp getting too dim. We could detect these problems when they arose, but did not have enough resolution to track performance degradation.
Our next approach was to use a set of 12 BCRA tiles. We picked on up for not too terribly much on fleabay. Absolute measurement accuracy was not something we could determine, primarily because of the difference in the measurement geometry between the reference values and the 45/0 geometry all our spectros use. Following the research reported on above, the cyan tile did indeed show the best correlation both between our Spectrolinos and the values GMB and X-Rite gave when the instruments were sent in for calibration. (A single cyan tile
costs $224 - not that bad. We later had the opportunity to have our tiles measured by a reference-grade, 45/0 instrument, but that had no real bearing on instrument tracking. We used the same methodology as before for tracking shifts in the spectrophotometers that could not measure the tiles; i.e. read a chart on the 'Linos and then remeasure on the other equipment.
The methodology we settled on for the last couple of years goes back to our original plastic tile strategy. The Spectrolinos still are checked using the BCRA tiles. We then use a Teflon sheet (this appears to be the one
) to measure the white response of the iCColor and iSis spectros. It took a fair amount of swearing to stencil the necessary positioning markers on the Teflon using a black marker, but the process is simple: Measure the Teflon reference on the Spectroscan, averaging many points together, measure "patches" (all white) on the other instrument, average and normalize to the Spectro results, and trend the values. With regular instrument use, we can see the effects of iCColor lamp dimming over a period of several months. When the values are sufficiently out-of-whack, the instrument goes back to X-Rite for repair. So far, we have yet to wear out an iSis -- the LED lamps do indeed have a longer life.
The Teflon sheets are remarkably stable. We bought a pack of them - 10 or 12 - and have replaced them when the surface gets damaged. We measured each sheet on Spectroscans initially, using 1000 samples per sheet. After a couple of years of dark storage, the sheets have not shifted color in relation to either a freshly factory-calibrated instrument or the BCRA tile set by more than the Spectrolino accuracy.