[argyllcms] Lost shadow detail in PS CS2 with Lab profile

  • From: Vallo Kallaste <kalts@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sun, 27 Dec 2009 14:51:35 +0200


Can anybody please tell me why using the Lab cLUT display profile cause
lost dark shadow detail? The data set for profile generation is same and
shaper+matrix profile (colprof -as) has no such effect in Photoshop CS2.
Please note that it happens only in Photoshop. There is no difference
using the Windows Picture and Fax viewer, which under Windows XP is not
color corrected, right? If using the simple Windows viewer it does not
matter if I set'n'load (dispwin -I) matrix or cLUT based profile. I'm
using the fine B&W picture from
The loss in dark shadows is quite noticeable. It's best seen in the upper
right crop with wooden beam where the wall turns mostly black,
particularly below the beam. Of course it's noticeable on the other places
also, on the radial gray gradient and the carved stone ceiling which loses
lots of texture. The photo looks best using L* not gamma based tonal
curve, but this is subjective. I don't know anything about L* except that
it's pushed by some calibration software makers and that the radial gray
gradient looks the best by using it. Best as in "visually linear" and
"having the least sized black spot in the centre". But it doesn't matter,
the effect of Lab cLUT vs. matrix profile is present also when using L*
tonal curve. I did the profiles using the following flow:
dispcal -v -yl -o -m -qh -g2.2 3008WFP-2.2
targen -v -d3 -g254 -f1200 -c3008WFP-2.2.icm 3008WFP-2.2
dispread -v -yl -k3008WFP-2.2.cal 3008WFP-2.2
colprof -v -qh -D"3008WFP-2.2-Lab" 3008WFP-2.2
colprof -v -qh -as -D"3008WFP-2.2-smatrix" 3008WFP-2.2


Vallo Kallaste

Other related posts: