[argyllcms] Re: Custom Illuminant
- From: Roger Breton <graxx@xxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Mon, 07 Jul 2014 16:11:29 -0400
I like to use eciRGBv2. I'm a D50 "guy", what can I say ;-)
/ Roger
-----Original Message-----
From: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-bounce@xxxxxxxxxxxxx]
On Behalf Of Brad Funkhouser
Sent: 7 juillet 2014 14:40
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: Custom Illuminant
When AdobeRGB is a little too small, and ProPhotoRGB is just too big, try
Bruce Lindbloom's BetaRGB, it might be just right.
- Brad
> On Jul 7, 2014, at 9:18 AM, <robert@xxxxxxxxxxxxxxxxxx> wrote:
>
> << How does the gamut mapping know that no mapping is required ? If
> you tell it the source gamut is ProPhoto, then it will think that lots
> of gamut mapping is needed, since the ProPhoto gamut is so much larger
> than a printer !>>
>
> Well that has finally clarified that point for me! So with Perceptual
> the whole source gamut is squashed down to the destination gamut, even
> if all the colors are within the destination gamut. This means that
> in a Perceptual mapping from ProPhoto to print, colors will be
> compressed resulting in desaturation of the image, particularly of the
> more saturated colors nearer the print gamut boundary.
>
> So the following strategy might make sense for a Relative intent
conversion:
> - Going from ProPhoto to print, make sure the colors are more or less
> within the destination space to avoid too much clipping.
>
> 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.
>
> I did a comparison of a 1-step ProPhoto [Perceptual to Print
> conversion] with a 2-step [ProPhoto to AdobeRGB conversion, followed
> by an AdobeRGB Perceptual to print conversion]:
> - If the original image colors are all within the AdobeRGB gamut there
> is quite a difference if the print gamut is much smaller than
> AdobeRGB, but none if it is of similar size.
> - If the original image colors are outside the AdobeRGB gamut, the
> 2-step approach is significantly better even if the print gamut is
> very close to the AdobeRGB gamut.
> This is a bit puzzling because I would have expected a difference in
> all cases (if the full ProPhoto gamut is squashed down in a Perceptual
> conversion).
>
> 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.
>
> Robert
>
>
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