Shmetamerism
Shmetamerism
- Subject: Shmetamerism
- From: Peter MacLeod <email@hidden>
- Date: Tue, 30 Oct 2001 09:28:57 -0800
In Roy Berns' "Billmeyer and Saltzman's Principles of Color Technology"
(Wiley & Sons 2000) there are the following definitons:
metamerism: the usual one that us color geeks think of: colors with
different spectra that have the same colorimetric coordinates for a
*single* viewing condition, and hence look the same to a typical
observer. A pair of such colors are called a metameric pair.
illuminant metamerism: If a metameric pair no longer matches after
a change in illumination, then the pair is said to exhibit illuminant
metamerism.
observer metamerism: If a different observer views a metameric pair
as no longer matching, then the pair are said to exhibit observer
metamerism.
I had not run into the definitions of "illuminant metamerism"
and "observer metamerism" in earlier color science literature, but
they do seem to be the terms we're after, even though they seem a
little clunky (i.e. illuminant/observer metamerism is when metamers
are no longer metameric..hunh?), but I guess they'll do. (Maybe
"illuminant shmetamerism" would be better, since the metameric pair
no longer matches under a change in illuminant :)
Therefore the Epson pigments exhibit illuminant metamerism, eh?
--Peter
BTW there are
At 10:42 AM +0100 10/29/01, Rudy Vonk wrote:
Bruce Fraser wrote:
> When the subject of color appearance shifting with the Epson pigs
> under different light sources came up, I immediately thought of it as
> a metamerism issue, but some folks were uncomfortable with using the
> term 'metamerism' since we were discussing one sample -- a single
> inkjet print.
"Haplometamerism", perhaps? :-) (I am reminded of Woody Allen playing a
friendly poker game in one of his movies and proclaiming to have
"five semipairs"...)
> One fudge for this is to treat the desired appearance on screen as
> one sample, and the print under the lighting that "works" as another.
> Then you have a classic case of metamerism, as defined above.
With the greatest of respect, I would beg to differ. Even if you call
these objetcs the "two samples" from the definition, we are definitely
not viewing them under "one light source".
On the semantic principle, I agree with Bob Binder:
> C. David may be correct, but I fear if we allow this to happen, we risk
> diluting the original and correct meaning of the term. Maybe this is
> advancement, but in my opinion, it is not.
When two phenomena are not the same, we cannot meaningfully discuss them
by giving them the same name.
I think most of us would be astonished if we found one sample (e.g. a
print) looking the same under five diferent light sources. So what we
are worried about in the case of the Epson prints is the *degree* of
something which we otherwise accept as perfectly understandable. Rather
than applying the term we are looking for (or my "haplometamerism") to a
single sample that looks different under two illuminants (perfectly
unsurprising), perhaps we should apply it to a single sample that looks
the same under different illuminants? (And then begin to look for
combinations of dyes, pigments, substrates, etc. that will achieve it.)
--
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Rudy Vonk
Oviedo, Spain
<email@hidden>
+34 607 354100
You can't always want what you get.
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