[argyllcms] Re: Calibration issues using argyll

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 10 Sep 2008 11:55:29 +1000

Steffen wrote:
But what I don't understand then is this: why does iColor seem to do a better 
calibrating the neutral axis than argyll?

What do you mean by "better" ? Better looking, or closer to the target ?
If the latter, have you measured it ?

Shouldn't this effect be the same no matter
which software is used to do the calibration?

Not at all. Each package almost certainly sets the calibration
targets in different ways, and goes about matching those targets
in different ways.

Would there be a way to combine the
calibration adjustments done by iColor with the profiling done with argyll? 
just meshing the two together obviously would be the wrong approach, and iColor 
does of
course not produce .cal files.

Not easily, since software like iColor probably doesn't break out the
calibration, but only embeds it in a profile.

The software didn't come with the Eizo. I bought the colorimeter after using the
Spyder2 for a while because the results were not satisfactory. iColor also does 
seem to be attuned to the Eizo in any special way, as I cannot see any 
reference to
what special display is used, except for the type being an LCD (which has to be 

Well then, either iColor is doing something different with the instrument
readings, or it is creating an ICC profile with some technical difference,
such as the way it deals with the white point adaptation. Some packages
make the absolute colorimetric white point appear to be D50 in display
profiles, even though that's not the display white point. Argyll doesn't
do that, it makes absolute colorimetric consistent with the raw measurement

manually). Although of course different software may have different approaches 
measuring these things. But then again, how can one be certain which result 
would be
preferable? I think this is a general problem regarding this topic and would be 
exploring. The iColor Software supports a test of the calibration results 
according to
UGRA standards. Yet again I cannot say if it has any relevance. Also, I am only 
able to
check profiles created by the software itself, not third-party profiles created 
Argyll. Maybe there is a tag I can change to trick it into doing it. I will see 
that later.

You can verify profiles using argyll's profcheck, but note that this
checks the absolute colorimetric table against the raw readings (.ti3 file),
so a profile that makes absolute colorimetric appear to have a D50 white
point will fare badly.

I'm running Windows XP (32 Bit) with the latest release of ArgyllCMS.

OK, try out <http://www.argyllcms.com/dispcal_win.zip>, and set the (new)
-A parameter to some value between 8.0 (the default) and 1.0. e.g. try
4 to start, or even 2, and see if it changes the coloration near black.
Note that a value of 1 will create a linear blend between the white point
hue and the black point hue.

Graeme Gill.

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