Re: Creating ICCs with pigmented inks
Re: Creating ICCs with pigmented inks
- Subject: Re: Creating ICCs with pigmented inks
- From: Dan Reid <email@hidden>
- Date: Thu, 11 Jul 2002 16:42:28 -0600
On Thu, 11 Jul 2002 17:50:51 +1000, Graeme Gill <email@hidden>
wrote:
>
Alexey Gribunin wrote:
>
> >>Yeah but there is only what - one of these apps available? Profile City's
>
> >>app is the only one I can think of that will compute something other than
>
> >>D50 LAB from spectral measurements.
>
>
>
> Logo ColorLab also can do this. I thought about color matching for non D50
>
> light but I don't know how to make further color conversion. E.g. Photoshop,
>
> as I know, uses D50 as internal PCS. So even if we have measurements with
>
> white point other than
>
> D50, we can do nothing with it. Or am I missing something?
>
>
The ICC format doesn't allow for recording the particular illuminant
>
spectrum, nor does it represent the profile information in a way
>
that allows the illuminant to be changed after creating the profile.
>
The illuminant spectrum therefore becomes "part of the profile"
>
(implicit in that profile being right for a particular set of
>
viewing conditions), just as the mode of a printer, the paper type,
>
the DPI etc. make a profile appropriate for a particular set of
>
conditions. The profile will be a closer match to what we actually
>
see under those viewing conditions.
>
>
[The Argyll CMS has supported arbitrary illuminant spectra for some time.]
>
>
Graeme Gill.
If I remember correctly, and maybe I am not, there is viewing tag available
in the ICC spec to indicate what the viewing conditions are. Now I don't
know of any product that uses this tag but I believe it does exist in the
ICC spec. How it would be used is beyond me.
There are a couple (literally) profiling products that do allow a
different illuminant to be used in PCS calculations. This is only possible
with spectral measurements and not colormeteric measurements since
colormetric measurements assume a white point of D50.
Logo ColorLab is an unsupported, no documentation, you're on your own color
utility application. If you know what you are doing it can do some really
nifty things aside from using different illuminants in colormetric
calculations. Again spectral measurement data is required to compute
colormetric data with a different illuminant than D50.
--
Dan B. Reid
RENAISSANCE PHOTOGRAPHIC IMAGING
http://www.rpimaging.com | email@hidden
Toll Free: (866) RGB-CMYK
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