[argyllcms] Re: Am I stupid or is it something else... my color management sucks.

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Thu, 15 Apr 2010 14:37:13 +1000

Magnus Berg wrote:
New try with a new Spyder 3, but still not satisfied.

dispcalGUI run this:
dispcal -v -d1 -c1 -yl -P0.474187380497,0.455830388693,1.0 -qh -t6500.0 -b140.0 -gs -f0.0 -a13.8 -k0.0 -A4.0 -B0.5 colprof -v -qh -aX

I got a perfect greyscale. From black to withe with all tones. But the calibration gave a red cast to some tones on the screen. The color #BEBEBE for instance. I got that color in my filemanager and then I take a screenshot it showed up perfect, as I can se it, in Gimp. Then I look at the vitpunkt.tif and svartpunkt.tif (Swedish for whitepoint and blackpoint - it shows neutral tones from tone 255 to 244 and tone 0 to 22 - download here http://www.profiler.nu/filer/Skarm.zip ) I see red casts in some of the tones. This occur both in color managed Gimp and in not color managed applications.

It's hard to help unless you are more specific about what you
are doing. You will probably find that the process of
figuring this out will help a lot in understanding the situation.

When you say "I got a perfect greyscale", what exactly
are you referring to ? What were you evaluating, how ?
Are you referring the calibration, or both the calibration
and profile ? What profile processing is being applied
(ie. what's the source profile, what intents are being used,
what CMM is being used/what's the application doing to things ?).

As soon as you start mixing in various applications that have
non-obvious behaviour, and it gets very hard to follow.

Both svartpunkt.tif and vitpunkt.tif have an embedded AdobeRGB
source profile. How was that dealt with ? Were the colors
converted from AdobeRGB to your screen, or were you ignoring
the source profile and using the numbers ?

Note that if you are using an LCD screen, that the dark tones
will (most likely) change color in an attempt to get the darkest
black point (dispcal -k0). This is because typically LCD screens
do not have matching color black and white points.

And then I locket at pictures in Gimp and Geeqie they looked the same but in Firefox then look like in not color managed applications. I must say that in Gimp and Geeqie most of the color has disappeared, the colors looks out washed. My pictures have never looked so dull. But I suppose that it can be alright, and that it is something wrong with Firefox.

Without an intimate understand of how these applications handle color,
it's not possible to comment. If your aim is to evaluate the
calibration and profiling, it's best to avoid using such tools
unless you understand exactly what they are doing.

It's perfectly reasonable to try and figure out what such applications
are doing, but that is a separate issue, and shouldn't be mixing in
with calibration/profile evaluation if you wish to retain your sanity !

The place to start is with dispwin. "dispwin -m" will go though some simple
test values. You can choose to load a linear calibration or the calibration
in your profile. You can measure values if you want (see spotread,
and particularly the -dw mode). You can setup your own test values in a
file and play them back using the -G option. You can manually convert from
source spaces to your display space and know exactly what's going on and
what numbers result using icclu. Once you know what the calibration
and profile are doing, you can start cross checking against applications.

I read the little discussion here about different profiles. I chosed to do a 'XYZ LUT + MATRIX' profile.

Color management will soon drive me nuts. There are questions like can I trust the Spyder 3 and have I set up color management right in Gimp and Geegie. In Gimp I have done like this:
Mode of operation:* Color managed display
*RGB profile:* None
*CMYK profile:* None
*Monitor profile:* None
/Try to use the system monitor profile/ = *Yes*
*Display rendering intent:* Perceptual
*Print simulation profile:* None
*Softproof redering intent:* Perceptual
/Mark out of gamut colors/ (grey) = *No*
*File Open behaviour:* Ask what to do

Those that are familiar with Gimp will have to comment.

Graeme Gill.

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