OK. I create a new CMYK document in Photoshop to which I assign my faithful Kodak XP Approval ICC profile. Therefore, anything I see onscreen should reflect (relatively or absolutely) the appearance of CMYK colors as rendered by the XP.
Intuitively it should. In actuality it doesn't. Let's call this the 'ICC color blindness to pure primary colors' test.
A 100C patch, a 100M patch, a 100Y patch and a 100K patch.
You got it right! Good to be clear on that point!
You mean, send those CMYK patches to the Approval, as is, unmanaged. Done.
Great!
I lost you. See my post of Thursday or Friday where I was describing a situation where the two devices, proof and LCD, matched each other to a very low deltaE degree, albeit with a slight overall appearance mismatch.
I remember that post and I believe you but this test shows something different.
Not only it would be counter intuitive but it would be against the underlying principles of ICC color management,
I totally understand where you're coming from but stick with me here.
So you've done all three steps. You're looking at the proof with the 100% primary ink patches in a light booth next to your color managed monitor showing the digital file with the XP profile assigned. You and I intuitively know that the proof SHOULD match the monitor and vice versa. However, I've done this test very recently and many times in the past and I can assure you nothing could be further from the truth. Pull out that spectrophotometer for those interesting results I mentioned earlier.
Well, I'm sure some people on the List will argue the contrary, Kevin. Since, by definition, the CMYK characterization *is* the 100% "accurate idea of what those CMYK numbers mean" -- otherwise, we're all lost.
Not at all! This is simply what color management is all about. ICC technology unshackled us from the concept that there is one and only one CMYK. It tells us that CMYK numbers alone are meaningless without assigning an ICC profile which gives context to the numbers. However you wish to quality control the color behavior of the output device means very little just so long as you can get the device to behave the same way as when it was profiled. To put it another way, CMYK values without an ICC profile is much like saying 'my file is 300dpi' without saying what the physical size is.
The new SWOP rules state that certified SWOP proofing is no longer a visual thing but a rigourous deltaE matching exercise
Even today, we find a wide range of SWOP certified proofers whose ink density, dot gain and neutrality curves simply do not match SWOP presses yet many say they provide an adequate (even preferable) visual match to the press. This supports the idea that densitometric QC and CMYK numbers do not have to agree to give the same color result, Inversely, densitometric QC and CMYK could agree perfectly and give radically different color results. This simply means we have to create 4C separations into the profile that properly describes the color behavior of the intended output device.
Again, an ICC output profile is bi-directional, by definition. It has a table in for decoding the appearance of color from CMYK percentages, and, as you say, it has a table (three, to be exact) to be used for separations.
I suggest when CMYK numbers are removed from their ICC context (we assign a profile other than the profile used to generate those CMYK numbers) then we lose a large degree of color predictability because we are uncoupling the CMYK numbers from the table which generated them. This uncoupling is what I call 'CMYK backwards'. A more extreme example would be 'Mystery Meat CMYK', or an untagged 4C file whose numbers do not correspond to any known profile separation.
If you have time, lets complete a peer review of 'ICC color blindness to pure primary colors' and see if we can find agreement on this and then see if we can somehow make some sense of the experiment.
Kevin Muldoon
TrueBlueDot
Fine Art Reproductions
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New Haven, CT 06511
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