[argyllcms] Re: Reproducing watercolor on watercolor paper?

Ben Goren wrote:
Now...I don't know what to do to get a good print of the art on the watercolor paper. I've done two experiments with gamut-mapped device link profiles. The first used perceptual intent and the second absolute colorimetric. The perceptual looks close, but the contrast is low, it's a bit undersaturated, and the printer still lays down a lot of ink on the unpainted parts of the page. Absolute colorimetric pretty much takes care of the contrast and saturation...but it lays down buckets of ink on the unpainted areas. 

There are two approaches to reproduced with a non-white paper color.
Either treat it as relative colorimetric throughout, or as absolute.
The former should be guaranteed to reproduce the white point almost exactly
(ie. lay down no ink for white) while the latter may not, depending
on the accuracy of the reproduction. For input the white point can
be slightly inaccurate on any particular image though, so some
manual adjustment to set the white exactly for each image can help.
(ie. scale the RGB so that white equals the white point RGB, or
something equivalent).

Note that using -u for the scan profile locks it to be absolute.
There is a way of fine tuning the absolute white point reproduction
with you are using a device links, using the -w flag of icclink,
but not if you are using a conventional "dumb" cmm.

I'd try a relative colorimetric input profile with a relative
colorimetric output intent as a first step, and see how it
goes from there.


Well, the good news is that I just got a test print I could live with.
The bad news is that it was on the last sheet I had for testing -- but
I can get more paper, so it's not that bad. 

Sorry, I've been a bit busy...

Graeme Gill.

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