[argyllcms] Re: dispwin vs xcalib loading LUT

  • From: Frédéric <frederic.mantegazza@xxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 1 Jan 2007 11:28:27 +0100

On Monday 01 January 2007 05:26, Graeme Gill wrote:

> What do you mean by "2.2 gamma profile" ? The Argyll profile looks
> appropriate for a CRT display with a native gamma slightly higher than
> 2.2. The vcgt tag corrects this to gamma 2.2, and the profile device
> curves reflect an overall response of gamma 2.2. The other profile only
> make sense if it is working with a display with a native gamma of 4.8!
> (ie. native gamma 4.8 * correction 0.45 = calibrated behavior 2.2, as
> reflected in the TRC's gamma 2.2) - ie., it is a very peculiar profile
> as far as I can tell.

What I don't understand is how a profile set the gamma of a monitor? Is it 
done with [rgb]TRC curves? Then, the vcgtag curve is a correction to 
linearize the monitor response with given gamma? am I right?

> Not being the author of xcalib, not without some effort. Can you clarify
> a little how xcalib and dispwin behave on these two profiles (ie.
> description of four cases).

I attached another profile, from xcalib package (gamma 1). Here is a table 
to summurize what I see:

Profile         Loader         vcgtag       [rgb]TRC        I see
gamma_2_2.icc   dispwin        gamma 2.2    gamma 2.2       bright
    "           xcalib            "            "            normal
gamma_1_0.icc   dispwin        linear       linear          normal
    "           xcalib            "            "            dark
A901HT.icc      dispwin        linear¹      gamma 2.2       normal¹
    "           xcalib            "            "            normal¹

¹close to...



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