GMG / colour seps changes
GMG / colour seps changes
- Subject: GMG / colour seps changes
- From: Graeme Bulcraig <email@hidden>
- Date: Tue, 19 Feb 2008 13:10:15 +0000
Hi list,
been a long time since I was last posting.
I have had a very strange result from a RGB>CMYK conversion in the
latest version of GMG colorserver 4.5.
We upgraded a while ago, and I understand that they have altered the
way GMG converts from Adobe RGB to ISO COATED V2 (Fogra 39L) using
its CAMFLOW module.
The MX4 conversation (supplied by GMG) uses a combination of Relative
and Perceptual rendering intents to gain the best result.
Anyway, I had a nice Adobe RGB master file, with some subtle colours
and graduations in a light cyan / blue background.
We converting to 39L in GMG and proofed on GMG 250SM paper. Checked
Fogra bar with Basicolor . All within good delta E tolerance.
Proof looked pretty good, (if anything cyan colours a bit dulled, but
I assumed this was correct for proof).
Then we sent file to press and the resulting wet proof looked
dreadful. Near highlight were VERY dull / dense. It was as if the
2-4% highlight area has gone far too dark.
I assumed this was down to press conditions etc..
To cut a long story short, I did the same conversion to 39L (latest
ECI icc profile) in Photoshop and we wet proofed the job again and it
looked nearly perfect. The difference in the two CMYK files is pretty
big. Esp. in the yellow channel.
Why would there be such a discrepancy between two files that should
both sit together. One converted to 39L in Photoshop, the other in
GMG. But more importantly, why is the Photoshop conversation so much
closer to the original RGB?
Which is correct?
I know which one I prefer.... and its not from GMG.
Is the GMG software maybe assigning an incorrect profile icc profile
after its (non ICC) conversion?
I also made a Photoshop conversion to 39L in Perceptual, and it
looked closer to the bad GMG conversation.
Maybe I need to create my own mx4 with a heavy relative conversion in
GMG to make more judgments.
Just hoped someone else on list might be able to point me in the
right direction?
Many Thanks in advance
Graeme
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Touch Digital Ltd.
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