On 06/04/2013 12:44 AM, Stanley Smith wrote:
(I worked recently with Roy Berns and Sinar AG to develop a six-channel system that achieves accuracy on a SG ColorChecker of less that 1 CIEDE2000).
Stanley Smith Head of Collection Information and Access J. Paul Getty Museum 1200 Getty Center Drive, Suite 1000 Los Angeles, CA 90049-1687 (310) 440-7286
Considering the results above what is your opinion of the HP G4010/4050 (dual illumination mode) scanner test results Image Engineering published in this PDF ?: http://tinyurl.com/lqtk7wp About 4 DeltaE on an acrylic paint chart described as follows: "In addition an acrylic painting was produced using 23 acrylic colors which were mixed with black in 5 steps so that a total of 115 patches were created." Which most likely had between 8 to 10 pigment varieties if I consider the usual art paint offerings. Scoring on average <4 DeltaE on the other charts: "An IT8 target on Fuji crystal archive paper represents the photographic samples. A sample derived from the IT8 reference data was printed on three different ink jet printers the HP 9180 which uses pigment inks and the Epson Stylus Color 1290 and Canon i560 representing dye based inks." They all are based on CMY(K) mixes but at least had a CMYK pigment chart included. While your measuring unit is more strict, the Image Engineering DIY acrylic chart represents one of the many cases in practice. The CCSG chart may represent the average of jobs like that but is usually also the target to aim the profiling at. This desktop scanner is of course a poor man's solution compared to multi-spectral capture methods. I wonder whether this HP dual illumination method could be improved for repro work with scanners and cameras . There is an analogy to the X-Rite Passport CC dual illumination DNG profiling that seems to create a better color fidelity than a single illumination DNG profile even when the light conditions are kept consistent. The Passport target is limited and the RAW route probably not best for repro work (if I interpreted this thread correctly) but it would be interesting if that profiling step could be enhanced with say the CCSG target. HP Artist, mentioned also in this thread, works somewhat different but I expect that the developments were related. HP had a lot of research going in this field 10 to 5 years ago. -- Met vriendelijke groet, Ernst Dinkla http://www.pigment-print.com/spectralplots/spectrumviz_1.htm December 2012: 500+ inkjet media paper white spectral plots.