Re: Convert UV-excluded to UV-included
Re: Convert UV-excluded to UV-included
- Subject: Re: Convert UV-excluded to UV-included
- From: Graeme Gill <email@hidden>
- Date: Wed, 23 Dec 2009 00:39:31 +1100
Roger wrote:
If there was a way, IMO, to establish a-priori the amount of optical
brighteners in a given substrate, in absolute terms, on some kind of
industry standard scale, then, perhaps, this could be matched with a graded
system of optical correction. Perhaps.
The "standard" way of characterizing this is a bispectrum (that's a 2D Plot
of spectral response to spectral stimulus). Instruments that are capable
of measuring this are rare and expensive.
Because, you see, another important
consideration in this UV correction scheme is the "UV content" from the
light sources under *which* the substrate will be viewed: a fixed correction
maybe adequate for one kind of light source while not enough for another, or
too much.
This is also a difficulty. No low cost instrument measures to a small
enough wavelength to characterize the UV output of illuminants.
In the end, in my humble experience, the easiest fix for this is to avoid
substrate with optical brighteners altogether. How reasonable is that?
Given that any attempt to compensate for FWA effects is very dependent
on the viewing situation (because such a correction is for one
particular illuminant), then compared to using papers with large amounts
of FWA, this is probably a more robust approach. But keep in mind that
nearly all popular color reproduction is tri-stimulus reproduction,
and is done on some assumption about the viewing illuminant.
Graeme Gill.
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