[argyllcms] Re: fwa compensation unexpected results

As it should. If it's all working, the papers should now match (although,
maybe not perfectly, since adding the yellow will pull the L down.
If the L goes down too much, it's not a good match, and your reference
is out of gamut as far as the proofing paper is concerned.)


This is quite true... not easy to find proofing papers with L>=95, and
when so, they tend to be either very expensive or ridden with
brighteners.
Maybe the gamut mapping strategy for the white point (and vicinity)
should be optimized differently (than the rest of the profile), even
for absolute colorimetric.

They should be way out if you're viewing under D50. Your proof would be
expected to be about delta b = -5, too blue. If it's not the case, then
either your profiling system is broken, or you're not viewing under D50.
If they do match quite well and your profiling system is not broken,
then you're got a better match by fudging the instrument illuminant to
be closer to your actual viewing illuminant by switching in the UV filter.
In or Out, only two choices. Argyll's FWA compensation has more subtlety
than that.


I usually view by the window, but I have to admit Lima's sky is a
permanent gray. We call it "rat's belly gray" and only in summer does
it recede a little to show the blue sky.

So I should start by measuring that illuminant? unfortunately I think
an Eye-One won't cut it, right?
Let's say I measure with my Eye-One now and get the custom spectra of
my daylight.
- should I measure over various days (cloudy, sunny) and daytimes and
average it? or is it a standard saying "measure at noon"? I guess it's
always indirect measurement, right? (through a window)
- how would I "complete" the spectra towards lower wavelenghts? copy from D50?

Regarding the  -I flag in spec2cie... when dealing with common
spectros (Eye-One, DTP-70, etc) then I should always specify "A"
illuminant?

It seems FWA compensation in Argyll would only work if you have access
to spectral data for both your reference and your proof?

best regards,

-- Roberto Michelena
  Infinitek
  Lima, Peru

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