[argyllcms] Re: Making a composite profile, combining ti3 & colprof -r question

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 25 Jun 2014 15:41:14 +1000

Derin Korman wrote:

> This is a drum scanner coming in with RGB, going to an rgb working
> profile such as AdobeRGB before printed, channel crossing visible in
> rgb working space.

Hi,
        I'm afraid I'm not sure what you mean by "channel crossing" in
an RGB space, since there is no extra degree of freedom to cross over in,
like there is in CMYK space.

> I meant that if I take A.ti3 and make a profile, it will give 1 delta
> E, B.ti will give 1 delta E also on it's own, but once I combine the
> ti3s it gives a delta E of 2-3. (symbolic values) Is this because of
> the change of standard deviations? They are the same ti3 files, so
> there is no changes in the process or input values to colprof

There is a table lookup that computes a heuristic smoothing factor that
depends on the dimensionality, sample point density, and sample point 
deviation. By
duplicating the points you've fooled it into thinking there is a higher
sample point density than is actually the case, and it's used a higher smoothing
factor, resulting in a less tight fit.

Self fit doesn't say much about how well the device is being modeled though,
just how consistent the sample points are.

Graeme Gill.


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