[argyllcms] Re: spotread filters

  • From: "Jacques Warnon" <j.warnon@xxxxxxxxxxxxxx>
  • To: <argyllcms@xxxxxxxxxxxxx>
  • Date: Fri, 6 Jun 2008 15:41:10 -0400

Hello Gerhard,

>Btw, what exactly is the impact you are observing? How do you judge w/o
>any "good" reference measurements that your measurements are "bad"?

That is a major cause of my frustration.  How can I quantify something
without a measurable reference? :)

>if it is a fluorescence issue, then I would expect that a profile made
>from measurements with the i1 (no uv-filter) should be at least fine for
>viewing the print under a tungsten light source (since the i1 uses a
>tungsten lamp too). Is this the case? Do your prints generally change
>the perceived color significantly under different kinds of light sources?

My profiles seem to correct for a purple hue by adding yellow and cyan,
giving a very strong green-yellow cast to all my highlights, and even into
the midtones.  And this is highly visible regardless of the illumination.

White point adjustments and UV filtering (both hardware and software) do
have some effect on neutralizing the highlights a little bit.  But not
enough to make a difference, and hardly anything in the midtones.  

>And if it is an UV-induced fluorescence issue, then I'd expect to see a
>clarly noticeable difference when comparing the shapes of the
>reflectance spectra of the substrate captured with the i1 with and w/o
>UV filter. But of course fluorescence does not need to be necessarily
>induced by UV, but can be also induced by any other wavelengths too
>[only FWAs are designed in particular to turn UV into visible light].

Yes that's what I thought as well.  The fabric may have optically reactive
properties that I am not aware of.  After all, this isn't paper purposely
treated to appear more white.  That's why I think the effect is similar to
FWA for paper, but not exactly the same.  

I think I will be able to examine spectral data much easier now that I am
more familiar with Argyll.  And then perhaps with the use of spec2cie as
Graeme suggested, I can get an idea of what is going on.  I should be able
to analyze some date, rather than scratch my head at what comes out of the
"black box".

Thanks so much for the feedback!


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