Re: metamerism and metameric color - more
Re: metamerism and metameric color - more
- Subject: Re: metamerism and metameric color - more
- From: Roberto Michelena <email@hidden>
- Date: Thu, 21 Jun 2001 17:46:24 -0500
Ok, I've got what's going on with this thread that has people arguing.
Guys, a reflective sample is not a color itself!!!!
The problem arises from the usage of diverse terms as "color", "color
sample", "sample", "color stimulus" and such and everyone understanding
them their own way.
Some people, the most scientifically oriented ones, as Peter MacLeod or
Fred Bunting, and of course Wyszecki and Stiles, are correctly defining
metamerism as a phenomenom between two SPDs (Spectral Power
Distributions) and the Tristimulus Values that these produce.
An SPD is not related to an illuminant. The illuminant has already been
reflected by a body, and that has produced an SPD (or "reflected
spectrum" so to say); a new SPD, if one takes into account the illuminant
is an SPD too.
Reflectivity is not necessarily a constant spectral function for a given
body, either.
Other people are relating the phenomena to the physical printed patches
or "color samples"; that's not the environment in which metamerism is
defined. A printed patch is not a "color". A "color" is what a printed
patch produces under a certain illuminant.
So a "color" can't match another "color" under one illuminant and not
under another. Because once you are in another illuminants, they're not
the same colors anymore. They're the same printed patches, though.
So the thing is, "two printed patches produce two reflected spectras
under illuminant #1, and these spectras are metameric because they
produce the same color stimuli (tristimulus values); then the same
printed patches produce two other reflected spectras under illuminant #2,
and these spectras are not metameric because they produce different color
stimuli."
Is that clear, or what?
again: a reflective sample is not a color itself.
-- Roberto Michelena
EOS S.A.
Lima, Peru