[argyllcms] Re: Question on FWA of papers

  • From: Claas Bickeböller <lists@xxxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 26 Oct 2021 07:41:08 +0200

Hi Graeme,

please correct me if I'm wrong.
Argyll's FWA compensation is trying to estimate the correct colorimetry even if the measurement illumination is not matching the viewing environments illuminant. This is necessary if you cannot measure the SPD of the illuminant directly and cannot analyze the amount of FWA (this is what we do with our VFS solutions).
After having the correct colorimetry it is possible to create icc absolute colorimetric matches.
So the intended application is proofing.

But Argyll's gamut mapping is always relative to the paper's white point, correct?
This means that as soon as you do not use absolute colorimetric as rendering intent having the "correct" colorimetry does not help to achieve similar results on papers with different white points (it doesn't matter if the difference comes from fluorescence or not).
The reason is that the full adaptation to the paper's white point is an assumption that does not reflect reality from our experience.

Best regards

Claas

Graeme Gill schrieb am 26.10.21 um 01:41:

Garry . wrote:

Hi,

Under the D50 viewing booth, the RGB prints look different due to the FWA 
content. I can generate
D50 spectrum files with 100%, 110% and 120% UV content but not sure how to 
implement them or if
that will correct the overall problem. Not sure if custom profiles for each 
paper can resolve the
problem totally.
a simpler and possibly more accurate approach is to try using illumread 
(assuming you have
a compatible instrument): <https://www.argyllcms.com/doc/illumread.html>.

You could start by using the paper with the highest FWA to measure the
illuminant and then use that for all 3 of your papers.
I understand the papers will always appear different and appear more blue with 
the FWA. But is
there a way to compensate by creating profiles so that each paper assuming 
borderless printing has
the same appearance on the printed image. Basically, take into account the 
addition blue spectrum
of the paper so that all three images appear identical when placed side by side.
That's exactly what FWA compensation is designed to do.

<http://argyllcms.com/doc/FWA.html>

Cheers,
        Graeme Gill.



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