[argyllcms] Re: Cannot get calibration/profiling to yieldgoodresults, user error?
- From: "Alastair M. Robinson" <profiling@xxxxxxxxxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 02 Jan 2009 19:23:33 +0000
Hi,
I agree with Nikolay here - your monitor seems to have a poor gamut in
the red area, and that's resulting in colours being clipped, hence the
reds becoming a solid mass of the brightest red the monitor can manage.
By the way, is this a laptop screen with little adjustment, or a
standalone monitor? If you're specifying a target brightness or
white-point when calibrating the monitor, are you using the monitor's
controls to get close to those targets before running the calibration?
I ask because the LUT data is making a pretty heavy white-point
adjustment, which may not be helping.
Nikolay Pokhilchenko wrote:
The result will be image with minimum detail clipping and maximum perceptual
equivalence to the original. Such image will be displayed properly by any
software, either color or non-color managed.
The other thing you can do is create a gamut-mapped perceptual table for
the regular display profile.
Many display profiles have no perceptual table included, so even if you
choose Perceptual intent, they still effectively operate in Relative
Colorimetric mode. If your goal is "pleasing" results, not side-by-side
matches with commercial print job proofs, using a real perceptual intent
will help.
I've done this myself for a number of monitors which have poor blacks
and thus are prone to clipping shadows in Relative Colorimetric mode.
Note that to benefit from this, software has to use Perceptual intent,
not Relatively Colorimetric. GIMP can be told to do this. I'm not sure
which other software has a user-selectable intent, which have it
hard-coded, and which use Perceptual as that hard-coded default!
Anyhow, to create such a profile, try this:
# Create a copy of the .ti3 file so we don't over-write the existing
profile...
cp lcd-t-b100-g2.4-f0-k0-qhh-lut-200812232358.ti3
lcd-t-b100-g2.4-f0-k0-qhh-lut-200812232358_gm.ti3
# Now generate a LUT-based profile with a gamut-mapped Perceptual table:
# We profile a "reference" profile with the -S parameter - usually sRGB,
# though you could use AdobeRGB or some other working space profile
# instead,
colprof -S /path/to/whatever_working_space_profile_you_use.icc
lcd-t-b100-g2.4-f0-k0-qhh-lut-200812232358_gm
This kind of profile takes longer to generate, so be patient - add the
-v flag if you want to see the progress... The resulting file,
lcd-t-b100-g2.4-f0-k0-qhh-lut-200812232358_gm.icc will include gamut
mapping in its perceptual table.
Hope this helps,
--
Alastair M. Robinson
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