Hi Marti, >> So what happens if the D50 XYZ values in lcms2.h are changed to match >> the iccToXml illuminant values?
A possibly related question/observation: How is it that the profile header illuminant values are so resistant to changes in the lcms2.h D50 values? I tried several variations on the default (0.9642, 1.0, 0.8249) values, and began to think that as far as the resulting header illuminant values go, perhaps it didn't make any difference, that perhaps the header illuminant values were hard-coded somewhere, because iccToXml always showed (0.96420288, 1.00000000, 0.82490540). But recompiling lcms with D50=(1.0,1.0,1.0) resulted in iccToXml showing the header illuminant as (1.00000000, 1.00000000, 1.00000000). So the D50 value in lcms2.h does affect the resulting header illuminant. But it takes a bit of shifting away from the standard D50 values! > Anyway, keep in mind this only applies on > matrix-shaper profiles, which are a *very reduced* subset of all > available profile types. On LUT-based output profiles, using those > values may probably make little difference, and since D50 is used to > normalize the PCS may have other side effects. My apologies for being so focussed on matrix profiles. But so far the open source RGB working space profiles are all matrix profiles. It seems color.org is introducing LUT versions of standard V2 matrix working space profiles, but I've never used them. Occasionally I use device LUT profiles, but those are made with Argyllcms (camera, monitor) or some third party (commercial printer). > Also, giving 0.000000 > or 0.000005 is a pure cosmetic question, since this is far below the > noticeable difference. For most people and most purposes and especially with 8-bit images, I agree the difference is so small as to not be noticed or even exist for 8-bit images. But if you work with high bit depth images, assign the lcms built-in sRGB profile to an image, convert to a working space that really is color-balanced (or vice versa) and do a fairly extreme saturation (e.g with channel mixer or by converting to Lab and playing with the ab channels or by moving the levels black point up quite a bit), nominally neutral colors will shift colors (I've tried, it happens). People who oversaturate their images might not care that gray and white now have a color cast. But then again, they might, and they might just be using the oversaturated layer as a means to some further editing goal. Also, for those people who make a new camera profile for every shot, perhaps shooting advertisements or artwork, color balancing is critical and a working space that isn't color-balanced might be another obstacle in their path toward perfect color control. I posted my profile-making code to my website in case anyone wants to check whether there are errors in the code: http://ninedegreesbelow.com/photography/lcms-make-icc-profiles.html Best regards, Elle ------------------------------------------------------------------------------ Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more! Discover the easy way to master current and previous Microsoft technologies and advance your career. Get an incredible 1,500+ hours of step-by-step tutorial videos with LearnDevNow. Subscribe today and save! http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.clktrk _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
