[argyllcms] Clipped shadows (bad gamut mapping?)

  • From: Andrew Lutomirski <luto@xxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sat, 3 Oct 2009 19:21:31 -0400

I'm profiling my laptop display, which can't display very dark blacks.
 I mainly want to use the resulting profile to display sRGB images
using the perceptual table, and I'd like it to map nicely between the
sRGB gamut (which, IIRC, contains black) to my display's gamut (which
doesn't contain black).

All of the LUT-based profiles I get from colprof, though, clip shadows
badly, as shown by xicclu -g -fb -ip, by lcms's icctrans (unless I
request black point compensation), and by looking at images that have
detail in the shadows.  (In fact, the profile isn't even always
monotonic for inputs below 30 or so, which seems strange.)

I'm running colprof as:

colprof -al -qh -v -S sRGB_IEC61966-2-1_no_black_scaling.icc x200s_6000

I've also tried the black-scaled version of the profile, ultra
quality, medium quality, and tweaking the -c and -d parameters.

What am I doing wrong?  I've read all the threads on shadow clipping
that I could find, and I didn't see anything helpful.

I've attached a tarball with the cal, ti1, and ti3 files.  I left out
the final profile, because it's rather large.


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