[argyllcms] Re: Printer grey-scaling profiling inaccuracy (using scanner)

Milton Taylor wrote:

b. I did use the -g option when I created the print chart. If I remove the grey wedges from the file, the profile will presumably not include LUT adjustments for these grey scale values, and so the profile will more or less leave the greys alone when they go through from PCS to printer device space. 

Umm - no. The profile has to map the R=G=B grey values to some
PCS value, and it will do so. When you link two profiles, the
output device values will be set by the inversion of that
mapping. There is nothing to make not sampled areas
tend towards the assumption that R=G=B maps to PCS neutral.

> But that assumes that this metamerism effect in
the scanner is affecting the neutral greys more so than the saturated colors. I have a suspicion this might be the case, as the visual match in the colors is actually not too bad. I think this will work, because in an earlier test I left out the grey wedges off the printed target, and did manage to get some neutral greys out of the printer. At that point I really didn't quite have a handle on what was going on, so it did not click then. 

You will probably get a different result. Whether it is better or
worse will simply be the luck of the draw - it certainly isn't the
result of neutral values being "not adjusted".

Graeme Gill.


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