[argyllcms] Re: Monitor calibration

  • From: Klaus Karcher <lists@xxxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Thu, 23 Jul 2009 14:06:11 +0200

nome cognome wrote:
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

I guess the reason for this bad evaluation result is a white point issue. Probably Spectraview writes D50 as media white point to the profile, but Argyll expects the actual white point of the display (otherwise the white point tag is pretty useless and it is impossible to recover the actual colors from an ICC v2 display profile!). The reason for this unfortunate situation is a arguable change (or "clarification") in the ICC profile spec regarding the media white point of monitor profiles (see below).

Specification ICC.1:2004-10 (Profile version "As specified in clause 9.2.25, for monitor profiles the mediaWhitePointTag shall be set to the PCS white point"

<http://www.color.org/advantagesv4.pdf>: "An important consequence of this clarification is that Version 4 profiles for RGB displays and working spaces should only contain D50 tristimulus values in the media white point tag indicating the transformation to the PCS white point."


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