Re: On the effect of florescence
Re: On the effect of florescence
- Subject: Re: On the effect of florescence
- From: Robin Myers <email@hidden>
- Date: Tue, 1 Mar 2005 20:17:50 -0800
On 1 Mar 2005, at 17:23, Graeme Gill wrote:
Robin Myers wrote:
The issue with FWAs is the amount of UV excitation available in the
print viewing environment is usually unknown and uncontrolled. Prints
viewed in illuminations low in UV light will not have the same look
as viewed in conditions with higher UV light. Also when comparing
prints made on different paper stocks, the amount of FWA in each
paper will give each a different appearance. Using the UV Cut filter
puts all the paper measurements to the same reference point.
That may well be true, but is it at all useful ? There's no point if
the resulting prints look different, because you've ignored the
effects of FWA.
Unless you are going to illuminate and view all the prints through the
same UV cut filter you used on the instrument, the FWA is there, and
you have
to deal with it.
The question here is how can a color management system be expected to
produce accurate prints on a paper with an FWA when the viewing
environment may have varying amounts of UV illumination? It makes the
paper white point a moving target.
There is also a problem with the measurement illumination. As noted in
my post to Mr. Breton (the L*a*b* information is included below), if
the spectrophotometer produces a different amount of UV illumination
than the viewing environment, how can an accurate print be produced? In
this instance if the spectrophotometer produces a UV illumination like
the Null filter, and the viewing environment has the equivalent UV
illumination of the D65 filter, then there would be almost 3 dE 1976 of
error in viewing the final print just in the paper white's b* value.
Filter L* a* b*
-------------------------------------------------
Null 96.40 1.38 -3.54
D65 1.133 2.81 -6.78
UV Cut 0.891 -0.53 2.45
(all values measured with a Spectrolino and SpectraShop 2 using the CIE
1931 2-degree observer, D50 illuminant)
For my clients, I advise them to use papers without FWAs for their fine
art prints. For their everyday prints I suggest measuring the printer
targets with the UV Cut filter on the spectrophotometer and that they
should not expect the print to be as exact a reproduction as their fine
art prints. To expect accurate prints with a paper employing an FWA is
unrealistic.
Robin Myers
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