[argyllcms] Re: Monitor calibration

  • From: nome cognome <darkbasic4@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Thu, 23 Jul 2009 13:13:13 +0200

2009/7/23 Graeme Gill <graeme@xxxxxxxxxxxxx>:
> the above discrepancy
> may actually reflect the inaccuracy of the generic instrument calibration
> matrix that Argyll has to use, rather than any deficiency in Spectraview.

I started thinking Spectraview II was not so good after checking the
profile I made with it:
Profile check complete, errors(CIEDE2000): max. = 14.525016, avg. =
5.885476, RMS = 6.473750
Same test chart used before. An average error of _6_ and a maximum
error of _15_! Unbelievable!

> I'm not sure why you are referring to the DE 2.7,
> which is the hardware calibration white point delta E, since
> the profiles will represent the behaviour of the device as
> it is, and hence are not affected by any absolute white point
> inaccuracy's.

In the real world the accuracy of the calibration affects the goodness
of the profile.
Since the white point was wrong I (wrongly) thought that the
calibration too could be of poor quality.

> Without access to
> the device in order to look at all the details, it's hard
> to explain exactly why certain combination work as they do

> 200 points it's probably too small a number for verification
> checks though. 1000 would be better.

Every manually-set setting that affects the calibration is overrided
by Spectraview II before doing the calibration (in my previous mail I
linked screenshots of the Spectraview II settings).
I'll repeat the test with a LUT profile and 1000 patches.
[I used few patches and shaper/matrix because my real problem is with
photoshop soft proof and I was also doing some tests trying to solve
it. I'll open a thread about it as soon as I'll have gathered enough
information about it.]

One more question:
This[1] is the linear curve loaded in the monitor if no calibration
software are installed in the system (here[2] you can see the dump).
This[3] is the non-so-linear curve which both Spectraview II and
Argyll consider linear and load in the video card LUT before doing the
calibration (here[4] you can see the dump).
I cheched it in my PC (I have an Ati) and in another PC with an Nvidia card.

Thank you,


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