[argyllcms] Profile input white not mapping to output white

  • From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Thu, 22 Nov 2012 13:31:03 -0700

First, happy Thanksgiving to all!

I'm photographing some artwork against a white seamless background, and 
intentionally overexposing the background to force it to pure white, while 
keeping the artwork within the exposure range of the camera. I'm shooting a 
target in the scene, linearly processing it with RAW Developer (after setting 
white balance, of course), and then doing the standard crop / chartread / 
colprof / etc. to create a profile.

Here's a thumbnail of the overall scene (with linear development):

image/jpg



Here's the image after applying the profile (created with no options given to 
colprof):

image/jpg


Except for the pale green background, I'm happy with the results.

If I use -u, the background remains less than pure white, but the tint is very 
much reduced (though the lightness remains about the same). I can mask it out 
reasonably enough in Photoshop, but that's obviously undesirable.

If I create a profile with -ag, the background is pure white, but both by the 
numbers and by eyeballing it the quality is much diminished. If I use -as, the 
results are somewhere between the two, both in terms of a not-white background 
and quality otherwise. With -ax, the numbers are marginally closer but there's 
severe posterization.

I'm attaching a Zip file with what I hope are enough relevant files to 
reproduce what I'm doing, less the 27 Mbyte RAW file. I can, of course, supply 
that as well. In its place, I'm including a 50% scaled JPEG at 50 quality, 
which I hope should be "good enough."

Any and all help would be much appreciated.

Thanks!

b&

Attachment: help.zip
Description: Zip archive

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