Re: On the use of wide-gamut RGB working spaces
Re: On the use of wide-gamut RGB working spaces
- Subject: Re: On the use of wide-gamut RGB working spaces
- From: Koch Karl <email@hidden>
- Date: Thu, 09 Oct 2008 18:06:07 +0200
Of course, Klaus is right and I was wondering all the time, when
someone would comment on these 2 topics:
Klaus Karcher schrieb:
ISOcoated (in your example) couldn't care less about the input
space -- and that's where the gamut mapping takes place.
Gamut mapping is not a dynamic thing that looks at both input and
output gamut and the decides how to map. The mapping is fixed in the
output profile.
Thus a huge working space that´s actually fully used by the image, can
be clipped even in perceptual rendering intent when converted tzo a
smaller destination space.
Some profilers (basICColor print being one of them) let you specify
the assumed source when building an output profile and will map quasi
dynamically.
And, of course, DeviceLinkers can do that trick, when they calculate
the gamut mapping anew.
- matrix profiles can't make any gamut compression or expansion
This is why it may be dangerous to convert from a large into a small
working space. All these profiles (sRGB, Adobe98, ProPhoto
) are matrix-based and thus provide ONE rendering intent only:
colorimetric. And with Photoshop CS2/3 not even an absolute
colorimetric RI any more. So, you will always clip colors that are
outside the destination gamut.
- Lut profiles /can/ provide gamut mapping in both directions
(whether this makes sense or not is a different story)
It makes sense for the large-to-small direction at any rate. And that
´s why I make LUT profiles from working space profiles when I need to
convert from a larger to a smaller working space.
Again, a DeviceLink can do the trick here again, provided that the
linker does it´s own gamut mapping.
Best regards,
Karl Koch
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