Re: CMYK to CMYK Conversion question
Re: CMYK to CMYK Conversion question
- Subject: Re: CMYK to CMYK Conversion question
- From: Graeme Gill <email@hidden>
- Date: Thu, 05 May 2005 14:08:49 +1000
- Organization: Argyll CMS
Chris Murphy wrote:
On Apr 12, 2005, at 8:30 PM, Joseph Yates wrote:
We notice now when we convert from the old CMYK to the new CMYK
(either Relative Colormetric or Absolute) that the colors become very
unsaturated and the color balance is noticeable off as well. Some of
I would not expect a DeviceLink profile to miraculously solve this
problem. It starts out merely as a concatenation of the two profiles
you're already using. Depending on what makes the DeviceLink, you can
add special handling for the black channel, or preserve channel purity
with or without scaling (anything yellow only stays yellow only, no
contamination). But if you're seeing a lack of saturation in reds, or
blues, or greens, and you have a gray balance issue - those kinds of
colors are still going to render as they would using the original
profiles to create the DeviceLink. So I'd investigate the two profiles
and find out why this is happening - some 3D modeling, and also test
each profile to see if there is excessive gamut compression occurring.
Are you getting good conversions with both profiles separately? If so
I'd be suspicious about the A2B table in the source profile, responsible
for defining how CMYK is mapped to the PCS. You might try conversions
using the saturation intent and see if that gets you an improvement at
all (unlikely but worth a shot).
A device link can help solve this sort of problem if it is created using
a "smart CMM" approach to the gamut mapping, instead of simply concatenating the
individual profiles.
The reduction in saturation you see is likely to be the result of the
in built gamut mapping of the output profile, which is probably set for
a generic compression, or compression from an assumed RGB gamut.
Using relative colorimetric intent for both profiles may minimize
the gamut compression effects.
Loss of grey balance indicates inaccuracy in one of the profiles.
Graeme Gill.
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