[argyllcms] Re: Calibration issues using argyll
- From: Steffen <ssachse@xxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Wed, 10 Sep 2008 03:26:16 +0200
Thanks for your reply!
Graeme Gill wrote:
I think I've seen this sort of effect, and it was on an Eizo display.
I haven't seen it on other LCD displays. My impression though, was that
it was a viewing angle effect. Viewed directly in front of the
display the effect wasn't obvious, but viewed at an angle above
the display it became evident.
The only theory I can come up with, is that this type of display
really isn't capable of maintaining the target neutral axis hue
down to so close to the black point, due to viewing direction color
inconsistency near black.
But what I don't understand then is this: why does iColor seem to do a
better job calibrating the neutral axis than argyll? Shouldn't this
effect be the same no matter which software is used to do the
calibration? Would there be a way to combine the calibration adjustments
done by iColor with the profiling done with argyll? Because just meshing
the two together obviously would be the wrong approach, and iColor does
of course not produce .cal files.
It is quite possible that iColor (if it came with the Eizo) is using
a display specific instrument calibration matrix, while Argyll uses
the default instrument LCD calibration matrix. This would explain
some differences in the profile and apparent gamut.
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 not 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 set manually). Although of
course different software may have different approaches to 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 worth 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 by Argyll.
Maybe there is a tag I can change to trick it into doing it. I will see
about that later.
If you tell me which platform you are running on, I can make available
a version of dispcal with an extra option that would let you alter
the blend rate used to the native black point target, to see
if this improves the appearance of the calibration.
Graeme Gill.
I'm running Windows XP (32 Bit) with the latest release of ArgyllCMS.
Also, if you need any readings from the display, let me know. I would be
more than happy to provide you with any information necessary.
Steffen
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