[argyllcms] Re: Perceptual intent

  • From: Production <production@xxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 16 Dec 2014 21:38:32 +0000

On 16 Dec 2014, at 15:37, Ben Goren <ben@xxxxxxxxxxxxxxxx> wrote:
> For me, it's not just good, it's scary voodoo magic good. I don't care what 
> the numbers might have to say...I just lay an original watercolor and a print 
> side-by-side on my kitchen table underneath a set of SoLux track lights, and 
> the only way even the artist herself can tell which is which is by picking up 
> each and either feeling the paper or looking at an angle for the raised brush 
> strokes. Yes, there are very minor differences between the two that are 
> visible with close comparison...but the differences aren't enough to tell 
> which is original and which is copy.
> That's with Argyll's gamut-mapped perceptual rendering.

Although I like using gamut mapping and perceptual rendering there are some 
significant issues when the destination is a printing press.

Perceptual conversions to sheet fed print profiles like FOGRA39 are generally 
OK but there is a tendency to boost the saturation in yellows. This can look 
pleasing in pale skin but nasty in already saturated, darker skin tones (around 
the neck for example).

Warm tones in shadows are also boosted so that they are easily noticed and 
commented on when clients are viewing contract proofs. In version 1.6 the 
warmth in the shadows became so pronounced that we were unable to use it at all 
and still use 1.5 for RGB to CMYK conversions.

Perceptual conversions to high speed press profiles and/or those using uncoated 
media aren’t good at all. For a profile like PSO Uncoated I see results that 
are along the lines of the OP’s observations — so lacking in contrast that we 
could never send them to press.

I’m guessing that the problem here is that the numbers are mathematically sound 
but the physics of ink and dots on paper requires another layer of processing… 
and the sort of bending, distortion and clipping that would give some people 
nightmares :-)

I’m sure that a high quality print made with an Argyll profile looks amazing, 
but if the artist needs a CMYK conversion that will be printed in an uncoated 
exhibition catalogue I would use an alternative method.

Martin Orpen
Idea Digital Imaging Ltd

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