[argyllcms] Re: Custom Illuminant

  • From: <robert@xxxxxxxxxxxxxxxxxx>
  • To: <argyllcms@xxxxxxxxxxxxx>
  • Date: Tue, 8 Jul 2014 13:11:02 +0100


About your comment regarding the 1-step rather than 2-step process:

> And the following for Perceptual:
> - Do a Relative conversion from ProPhoto to AdobeRGB (making sure the 
> colors are more or less within the AdobeRGB space before the 
> conversion to avoid too much clipping).
> - Do a Perceptual mapping from AdobeRGB to print.

Yes, that's one way. Another is to feed in a smaller gamut as the source
into colorpof/collink -g. The smaller gamut could be from a colorspace
(iccgamut) or from the images themselves (tiffgamut).

> What would be nice would be to be able to make the smaller 
> intermediate working color space using tiffgamut/colprof (from a range 
> of typical images), but I don't see how that could be done.

I don't see why you would want to use the 2 step process, when a 1 step with
a smaller source gamut specified is more efficient.

The reason I'm thinking of a 2-step process is that:
- Step 1: ProPhoto-to-AdobeRGB is a relative conversion that will only clip
OOG colors.
- Step 2: The Perceptual AdobeRGB-to-Print mapping should have a lesser
flattening/desaturating effect than would a direct Perceptual
ProPhoto-to-Print mapping (since the AdobeRGB space is smaller than the
ProPhoto RGB space).

Reducing the Print gamut by using colprof -g won't improve the ProPhoto to
Print desaturation ... it will only make it worse (I think).

As I find out more about the different working-space options, I'm beginning
to think that a ProPhoto-to-BetaRGB Step 1 would be better than a
ProPhoto-to-AdobeRGB Step 1 as BetaRGB is still significantly smaller than
ProPhoto, but still bigger than my print or monitor gamuts.

Do you agree?


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