[argyllcms] Re: Absolute colorimetric - dark saturated colours excessively light

Graeme Gill wrote:

Colorimetric intent simply clips the colors to the closest point on
the gamut hull. Closest as measured in the space the gamut mapping
is represented in, which is either L*a*b* or CIECAM02 space.

OK. So would you think this file demonstrates expected behaviour for a device with poor black density?:

http://i14.photobucket.com/albums/a346/robinsonb5/IT8_Plain_Proof.jpg

Absolute colorimetric is generally use for hard proofing, where
the proof is intended to lie next to the original, and match it
as closely as possible. For this to work well, the instrumentation
needs to be as accurate as possible, e.g. preferable the same
spectrometer used to measure the sample patches of both the
target (input) medium, as well as the proof (output) medium.
Off hand, I would imagine the limitations of using a scanner
as a colorimeter would show up rather badly under such exacting
circumstances.

My printer profiles were built using the ColorMouse CM2C Colorimeter, not a scanner - and they're performing remarkably well (even the plain paper one) with perceptual intent.

I'm not looking for perfect proofs - I want to achieve two things:

1. I want to be able to sample paint chips with the colormouse and get a tolerably good match if I use the sampled value when creating a paint chart, and

2. I want to be able to do "colour photocopies" on the scanner, keeping colour accuracy as much as is possible (and clipping out-of-gamut colours as necessary.)

Neither of these applications need the kind of tolerances you're used to working with, but to my eyes the very dark saturated colours in columns 2-4 of the IT8 chart do seem to be wildly out.

Anyway, time to get some sleep, I'll investigate further tomorrow...

All the best,
--
Alastair M. Robinson

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