On the effect of fluorescence
On the effect of fluorescence
- Subject: On the effect of fluorescence
- From: Roger Breton <email@hidden>
- Date: Mon, 28 Feb 2005 10:37:16 -0500
I'm comparing two sets of measurements made from the same litho press sheet.
Up until now, I was under the impression that the UV-cut filter found on the
DTP41UV and, possibly, the Spectroscan (and other UV-cut fitted instruments)
would mostly affect colors with L* > 70, because colors in that range become
progressively affected visually by the hue of the paper which is the vector
of fluorescence excitation.
But, no, it does not seem that way in the face of some new evidence which
never occurred to me. Based on the two sets of data I'm working on, it's
plain to see that fluorecence seems to have practically no effect on solid
cyan (100%C with L*=56), surprisingly little effect on solid yellow (100%Y
L*=88), barrely detectable effect on a solid black, but what a difference on
on solid magenta (100%M L=46)! Almost 2 DeltaE, in fact. That's not just
random instrument variation.
And say that I thought that the net effect of fluorescence would generally
be to fool the instrument, and the profiler, to see more blue into colors
than there 'perceivably' is. Hence, the typical compensation of profilers to
throw more yellow into the mix to compensate for all that extra blue. But I
realize, now, I was wrong.
That could explain why uncorrected gray balance appears objectionably on the
green side?
Any ideas? Tales from the trenches?
Incidently, would anyone know the difference between X-Rite and
GretagMacbeth UV-cut filtration? Is there an ASTM standard on the
specifications of UV filtration, by any chance, or is it to the good
judgement of an instrument manufacturer?
I know, I know. Lot's of good questions for an ordinary Monday morning...
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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