[argyllcms] Re: Perceptual intent

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sat, 20 Dec 2014 15:28:34 +1100

Production wrote:

Hi,

> I’d be happy to send examples — I just need to find some that aren’t 
> commercially
> sensitive :(

There are a lot of test images out there:
<http://www.northlight-images.co.uk/article_pages/test_images.html>
<http://www.outbackphoto.com/printinginsights/pi048/essay.html>

etc.

can't one of those demonstrate the problems you see ?

> In the meantime, if you want me to separate any test images at this end using
> commercial prepress software, send download links to me. I can run those 
> through our
> system in minutes and you may find the results interesting…

I've got nothing specific to focus on - the last time around, tuning
the gamut mapping took some weeks and many hundreds of conversions,
so it is not something to be revisted lightly.

> On top of black generation and GCR controls, it’s really useful to have the 
> ability to
> increase/decrease contrast and control both clipping and compression *prior* 
> to
> building the device link.

Isn't that what photoshop is for ?
The whole idea is to have a predictable, well behaved workflow from
display to press, so that you can do the subjective tweaks using the
display, and then send it to the press, confident in what you'll get.

> Even after creating the device link, commercial products
> give us the option of directly editing the 4D tables to precisely control the 
> CMYK
> results from specific RGB input.

I'm unconvinced about the utility of editing images or profiles in printer 
device space,
unless it is to fix technical problems, or as a last ditch fix. You've already
clipped to the output gamut, so there is no scope to hand tweak the mapping, and
any subjective tweaks would probably be better done in a well behaved space.
[ It's also too close to the "bad old days" when the press man tried to get
  the print to match the proof by fiddling with ink levels, etc. ]

Graeme Gill.

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