Hi, > However with lcms2(git) I obtained a bluish output:
This is indeed a bug... too bad it was not caught on time for 2.1 Now it is fixed on GIT. The bug was swapping white points on input & output profiles. It affected display profiles only, if you use absolute colorimetric to, for example, simulate paper white on a printer profile it does not affect you. As Graeme already noted, the specs on ICC V4 are pretty messed out when regarding to absolute colorimetric intent. Now there is something called "ICC absolute", which is same that relative on display profiles and preserves paper white on output profiles. Basically the observer is assumed to be fully adapted to whatever illuminant being used to create the profile, this has severe implications on monitor profiles, and no effect on printer profiles measured under D50. So right now we have the v2 absolute, wich says nothing about the observer adaptation state and v4 absolute which assumes full adaptation. I tried to do my best in supporting all modes (v2 and v4) by implementing what the white paper below describes, a knob to adjust the degree of cromatic adaptation, a feature that may be useful for match-to-screen applications. http://www.color.org/ICC_white_paper_6_v2_and_v4_display_profile_differences.pdf Thanks for catching the bug! Regards Marti Kai-Uwe Behrmann wrote: > Hello all, > > after the previous post about absolute colorimetric rendering on the lcms > email list, I played with some tools to simulate a D50 print booth on > screen. > > lcms1 gave the expected redish result, to compensate for the too bluish > monitor whitepoint, with: > tifficc -t 3 -e -o D64_monitor.icc Farbe_sRGB_D50.tif out1.tif > > However with lcms2(git) I obtained a bluish output: > tificc -t 3 -e -o D64_monitor.icc Farbe_sRGB_D50.tif out1.tif > So the monitor is much more off from the light booth than with a non > absolute rendering intent. > transicc behaves similiar: > $ transicc -t3 -c 0 -isRGB_D50.icm -oD64_monitor.icc > LittleCMS ColorSpace conversion calculator - 4.0 [LittleCMS 2.01] > > Enter values, 'q' to quit > R? 128 > G? 128 > B? 128 > > Channel #1=0.4458 Channel #2=0.4906 Channel #3=0.6351 > Which is a similar bluish result as above from tificc (lcms2). > > > > All involved profiles are ICC v2.x . sRGB_D50.icc was embeded into the > tiff image. > > Btw. Argyll's cctiff showed almost no white point adaption, with: > Argyll_V1.3.0/bin/cctiff -v -i a sRGB_D50.icm -i a D64_monitor.icc > Farbe_sRGB_D50_nc.tif argyll_abs.tif > > Reading the V42 spec it says that the source media white point is > maintained on output media. I interprete this like, a D51 media white > point under D50 illuminant will appear on a D64 monitor as if illuminated > under D50. > > Hmm. Not shure if I miss here something. Any help to bring light on this > issue is appreciated? > > > kind regards > Kai-Uwe Behrmann > ------------------------------------------------------------------------------ _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
