Re: On the effect of florescence
Re: On the effect of florescence
- Subject: Re: On the effect of florescence
- From: Graeme Gill <email@hidden>
- Date: Wed, 02 Mar 2005 16:31:08 +1100
- Organization: Argyll CMS
Robin Myers wrote:
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.
Only if the viewing environment is not fixed. Given that the currently
available reproduction systems are tri-stimulus systems (not spectral),
it is not reasonable to expect high quality color matches under
varying or unknown illumination.
So, if your viewing environment is unknown or uncontrolled, don't
expect high quality matches. If it controlled and known, allow
for the illuminant.
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?
By allowing for (ie. modelling) the different illuminants effects on
the different amounts of FWA.
I agree that accurately measuring illuminants is currently much more
difficult than it ought to be, but this is something of a chicken and
egg issue (Applications that could use better illuminant characterization
don't exist because the instruments don't exist, the instruments don't
exist because no applications that could use the information exist).
There are ways around this issue in some common situations.
For my clients, I advise them to use papers without FWAs for their fine
art prints.
That's certainly one way of avoiding the issue, and making the
reproductions less dependent on the UV content of any illuminant.
It can be rather difficult to find papers without FWA though. I notice
that even some of the high quality proofing media has some
amount of FWA.
Another technique (appropriate for proofing) is to match the
two papers for both white point and FWA content.
> 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.
Not at all. Simply use a technique that models the effects of FWA under
the illuminant. See "A Practical Approach to Measuring and Modelling Paper
Fluorescence for Improved Colorimetric Characterisation of Printing Processes",
Graeme W. Gill, IS&T/SID Eleventh Color Imaging Conference -
<https://www.imaging.org/store/physpub.cfm?seriesid=4&pubid=303>
Graeme Gill.
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