[argyllcms] Re: monitor calibration - strange behavior

  • From: Alberto Ferrante <alberto.ferrante@xxxxxxxxxx>
  • To: "argyllcms@xxxxxxxxxxxxx" <argyllcms@xxxxxxxxxxxxx>
  • Date: Fri, 15 Feb 2013 23:26:25 +0100

Actually I think I found the reason of the inconsistency: even though I
double checked all the monitor settings in the past days, a setting in a
menu called "range extension" and incorrectly set on "auto" went
unnoticed. I think that in "auto" the monitor decides automatically if
the range extension should be used or not depending on the image. I
disabled it as enabling range extension increases gamma to 2.4 instead
of the "native" 2.2.
I also inserted 50 neutral patches (-g50 of targen) and the light grays
seem more neutral now (i.e., I do not have the feeling that images are
cold in the highlights anymore). I may add some more as I work a lot on
black and white images ;)

        Alberto Ferrante

On 02/15/2013 08:31 PM, Alberto Ferrante wrote:
> Graeme Gill wrote:
>>> Inconsistency between different reads in the same conditions. I just run
>>> dispcal -r multiple times without even touching the colorimeter.
>>> I've done the same with dispcal -R with much more consistent results.
>> It sounds like that explains your shift from 100 to 97 then ?
> Well, actually not... Let me summarize things a bit:
> * different reads done by using dispcal -R give pretty consistent
> results (about 101.5)
> * different reads by dispcal -r give pretty inconsistent results (97-108)
> * white point setting (option 2) in dispcal give reasonably consistent
> results (about 101.5)
> * the verification step of dispcal (repeated twice) gives a read of
> about 101.
> To me it looks like the problem is somehow in dispcal -r
> Yesterday night I tried profcheck on the icc profile by using 500 new
> patches and the results I got is the following:
> No of test patches = 512
> Profile check complete, errors: max. = 2.817538, avg. = 1.219014, RMS =
> 1.335181

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