Re: Epson Stylus Pro 9600 Extrachrome
Re: Epson Stylus Pro 9600 Extrachrome
- Subject: Re: Epson Stylus Pro 9600 Extrachrome
- From: Graeme Gill <email@hidden>
- Date: Wed, 17 Nov 2004 10:23:19 -0800
Roger Breton wrote:
What would you call then a reflective surface that 'disproportionatly' or
wildy change its appearance with two different light sources?
I'm not sure anyone has invented a word for that ! It depends of course
on the nature of the three spectrum involved. I could certainly imagine
designing three spectrum (the reflective surface and the two light sources)
such that the color appeared to change radically, even if the two light
sources appear "white" when viewed directly.
> I am talking
about an Epson 1280 print, on Epson glossy paper, that looks one way under
5000K, another way (yet recognizably the same) under tungsten but radically
different, all of a sudden, for no apparent readon, under window light? As
though you'd be viewing the print through a green filter.
We're rather sensitive to gray balance changes, and it's also possible
that there could be some FWA (Fluorescent Whitener Additives) effects happening,
if the relative UV content of the tungsten and glass filtered daylight (or
conceivably even ink fluorescence, although the manufacturers are being
silly if they sell such ink for proofing purposes).
The only way to resolve this scientifically would be to have the right instruments
available to measure the two light sources (including UV), and the print
spectra (including characterizing fluorescence).
There must be a way to operationalize the color appearance of the print
under various light sources. But I have no idea what it is. In principle,
the change in appearance of the print is predicted by simply integrating
using a different relative illuminant spectra. But I submit this technique
fails here because of some combination of Epson inks and substrate.
There is limited scope for manipulating this given 4 inks (although some
folks have attempted to do "spectral matching" with 4 inks, but the match
will be a bit limited). Creating a CMYK->CMYK transform that preserves
the source black generation may improve spectral matching.
In general though, the answer is simple but not feasible:
maximize the black in the output profile. This will give you the
best possible neutral stability under different lighting (though not
necessarily the best tracking to a reference print). It will also
give you the worst possible banding and "grain" appearance on the print.
Given a particular paper and ink set, it appears to be a tradeoff.
Graeme Gill.
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