Re: maclife.de
Re: maclife.de
- Subject: Re: maclife.de
- From: Uli Zappe <email@hidden>
- Date: Thu, 21 Aug 2008 21:36:25 +0200
Am 21.08.2008 um 06:07 schrieb Graeme Gill:
Yep, but as I wrote, that didn't seem to be ideal, either. Logo's
(i1 Match / ProfileMaker) behavior is somewhere in between, and
this seems to be the best.
I don't really see how you can be "somewhere in between". Either the
intent is absolute (not adaptation to the media white point), or
it's relative (full adaptation to the white point). While something
in between can be created, there is no ICC label for it (no "partial
relative colorimetric" intent is available.)
It's not the white point I referred to, but the expansion of
luminosity in the perceptual intent.
As I understand it, luminosity is usually expanded in the perceptual
intent, while in the colorimetric, it's not.
Let's say you have a luminosity of 5 in the Dmin patch and 90 in the
Dmax patch of your target, and for the simplicity of the argument
let's say you map 1:1 to RGB and ignore gamma. So Dmin would
correspond to 0.05 x 255 = RGB 13, and Dmax to 0.9 x 255 = RGB 230.
This is where the colorimetric intent would leave it at, whereas the
perceptual intent would expand luminosity to make the image look
brighter (at least that's how I understand it).
Obviously, you could do this full scale (map RGB 13 to RGB 0 and RGB
230 to RGB 255), or only partly, leaving a certain headroom for images
with Dmin or Dmax beyond the target patches (e.g. map RGB 13 to RGB 5
and RGB 230 to RGB 250) and avoiding that the images look "too
bright". That's what I referred to with "somewhere in between".
Bye
Uli
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Uli Zappe, Solmsstraße 5, D-65189 Wiesbaden, Germany
http://www.ritual.org
Fon: +49-700-ULIZAPPE
Fax: +49-700-ZAPPEFAX
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