At 10:31 PM -0800 12/20/07, MATT LARMOUR wrote:
>I am puzzled by a strange phenomenon in Photoshop.
>
>I take an RGB image, and convert to a CMYK output profile, using Rel Col intent *without* black point compensation.
>
>The image, on screen, appears to darken substantially. Most of the image is in-gamut for the destination profile. Checking the L* values of different areas of the image before and after the conversion using the eye dropper tool shows that the L* values are the same - which is what I would expect provided the colour is in-gamut for the output device. But, on screen it looks darker than the RGB version.
It's possible that the CMYK profile proofs dark. If the profile was built using black-backed measurements or something else contributed to dark measurements then it may MAKE satisfactory CMYK values but PROOF them poorly.
One idea is to convert to your profile and then ASSIGN a different CMYK profile as a test. Hopefully that CMYK profile is a known-good profile and very similar to your original CMYK profile's print process.
If the assigning brightens the image then a dark proofing transform is probably the issue.
You could also perform a number of other profile evaluation tests to see if it matches up with its measurement data, etc. ColorThink Pro's Guide will walk you through this if you are a user..
Regards,
Steve
________________________________________________________________________
o Steve Upton CHROMiX www.chromix.com
o (hueman) 866.CHROMiX
________________________________________________________________________
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