[argyllcms] OT Rambling Profile Questions

  • From: Idea Digital Imaging <qcore@xxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 7 May 2010 20:53:24 +0100

Not specifically Argyll-related but hopefully OK for the list...

I've been supplied with a profile for an uncoated paper that is behaving oddly.

The profile is here: <http://inside.rgb2cmyk.com/images/profile.zip>

The initial problem is that the images I'm working with have critical neutrals including black to grey vignette backgrounds etc and there's no GCR to help me in this profile. I've created a couple of variants in Profilemaker (GCR4 and MaxK) which give better results (I have used Argyll for this in the past but find adjusting black generation in Profilemaker a lot easier).

I've created device links in Argyll (perceptual intent, gamut mapping from source to destination profile) and the RGB to CMYK conversions are looking great.

But then I find that half of the images can only be converted in Photoshop because they are layered and need to retain those layers during the conversion. There are no gamut issues with these images but I do need to use a perceptual conversion because it usually provides more shadow detail with uncoated papers.

The odd thing is that the relative conversion looks fine in Photoshop but, when I select perceptual. all of the yellow drains out of the neutrals and I get a nasty looking, cold result :(

So, my first question is: Why does a perceptual conversion in Photoshop using this profile and the adapted versions I made in Profilemaker remove so much yellow from the images compared to relative intent? (The device links I made with Argyll don't do this)

And the second question is: What's the easiest way to stop this from happening so that I can get perceptual conversions in Photoshop that look more like my Argyll device link conversions?

And the third question arising from puzzling over this odd profile behaviour is: How do the different vendors of profile making software deal with perceptual conversions? Is there an established method or is it secret sauce?

They say that a "problem shared is a problem halved" -- which could be very useful as I've got to separate 128 images and output 9 A1 FOGRA proofs by Monday afternoon...

Martin Orpen
Idea Digital Imaging Ltd

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