I premise this message by saying that I am NOT a color scientist (though I
wish I was sharp enough to be one): just a guy who has been dabbling for a
few years in matters that have scientific ramifications, which he is still
trying to sort out for himself.
So, there went the introduction.
Now to what I wanted to ask: Metamerism vs Color Constancy.
First, a definition of the terms (taken from the great web site
<http://www.answers.com>):
------
METAMERISM
Metamerism is a psychophysical phenomenon commonly defined incompletely as
"two samples which match when illuminated by a particular light source and
then do not match when illuminated by a different light source."
["Incomplete" because metamerism can also be subdivided into sample,
observer, illuminant, and geometric metamerism]
------
COLOR CONSTANCY:
Color constancy is a feature of the human color-perception system which
ensures that the perceived color of objects remains relatively constant
under varying illumination conditions.
------
I am bringing this up because my poor insufficiently scientifically-trained
mind is trying to comprehend whether the term "metamerism" is currently
being used improperly in color management circles.
When we refer to inkjet prints as being "metameric" (a common buzzword these
days among the initiated to the growing sect of inkjet printing), do we
actually mean, instead, that they lack color constancy?
Metamerism happens between two samples (in sample metamerism, at least)
whose colors have different spectra. This spectral difference creates a
match under one illuminant (called a metameric MATCH) and a mismatch under
another illuminant (a metameric FAILURE). I have been unable to retrieve the
etymology of the word "metameric," but it seems that it refers to parts that
appear or ought to appear similar if not identical to one another (as in the
segments of the body of an earthworm, which are called "metameres").
If that is so, then a print cannot, by itself, be metameric.
So, if we use the word "metameric" to mean that a print changes its color
appearance under different illuminants, shouldn't we actually say that IT
LACKS COLOR CONSTANCY instead?
Please tell me if I am wrong about this, but if I am correct could we please
stop saying that inkjet prints are metameric, then?
Thank you.
--------------
Marco Ugolini
Mill Valley, CA
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