Re: (no subject)
Re: (no subject)
- Subject: Re: (no subject)
- From: Steve Upton <email@hidden>
- Date: Wed, 30 Jul 2003 09:53:20 -0700
At 4:25 PM +0100 7/30/03, Andy Fraser wrote:
>
Chaps,
>
>
Could someone explain something to me please? I have a CMYK file with an embedded ICC profile, if I convert it to Lab in Photoshop colorimetrically and then convert again back to my original CMYK colourspace again colorimetrically should the Lab values remain the same at points of the process? MY understanding is that they should, however when I try this the values change sometimes considerably. Anyone brainy enough to tell me why? Cheers!
I suspect the majority of your errors are due to rendering intents. If you want to do a round trip through a profile you should probably use absolute colorimetric in both directions. I have found sometimes that rel col works OK too.
It is understandable to think that rel col is not performing any color mapping. But, in fact it can be mapping color significantly as it maps all colors RELative to the white point of the new color space, then maps them back.
It can also depend somewhat in the source of the original CMYK. While the CMYK->Lab transform should be able to handle any CMYK thrown at it, It may do a better job with CMYK values that the profile itself generated (rather than some other profile).
Regards,
Steve
________________________________________________________________________
o Steve Upton CHROMiX www.chromix.com
o (hueman) 866.CHROMiX
o email@hidden 206.985.6837
o ColorGear ColorThink ColorValet ColorSmarts ProfileCentral
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| | >(no subject) (From: Andy Fraser <email@hidden>) |