RE: Shmetamerism
RE: Shmetamerism
- Subject: RE: Shmetamerism
- From: "Fred Bunting" <email@hidden>
- Date: Wed, 7 Nov 2001 15:53:49 -0800
- Thread-topic: Shmetamerism
I disagree that the definitions of metamerism as given by Fields, by
Hunt, by Berns, the one given on this thread by Bruce Fraser, and a few
others we've been hashing, are somehow inconsistent. They are all
perfectly consistent and equivalent.
People are getting confused into thinking that the following are three
different statements:
Statement 1: Two stimuli *known to be spectrally different* produce a
match to a given observer." (Note my emphasis.)
Statement 2: Two color samples match (to a given observer) under one
illuminant, but fail to match under a second.
Statement 3: Two stimuli match to one observer, but not to a second.
Look closesly and you can see that these are three perfectly equivalent
statements ... just different ways of stating the *exact same fact*.
Given any one of these three statements you can predict that the other
two are also true.
Statements 2 and 3 are basically just observational experiments we can
perform to prove that Statement 1 is true. They are experiments that
prove that the two stimuli that produced the match are spectrally
different.
Or you can say that knowing that Statement 1 is true predicts the
observations in statements 2 and 3.
- If two stimuli are spectrally different and are the result of looking
at two color samples under one illuminant, then we can prove that there
exists a second illuminant under which the two color samples will fail
to match.
- And if two color stimuli are spectrally different, then they will fail
to match to a second observer with a different response.
But it's very important to make these three Statements completely:
Statement 1-incomplete: "Two stimuli produce a match to a given
observer." If you don't clarify that we *know the two stimuli to be
spectrally different* then we don't know for sure that we have
metamerism. If the two stimuli might be spectrally identical, then this
is *not* metamerism.
Statement 2-incomplete: "Two color samples match under one illuminant."
If we don't also know that they fail to match under some second
illuminant, then we don't know that we have metamerism. If they matched
under *all* illuminants, then the two color samples must be spectrally
identical, and this is *not* metamerism.
Statement 3-incomplete: "Two stimuli match to one observer." If we
don't also know that they fail to match to at least one second observer,
then we don't know that we have metamerism. If they match to all
observers, then the two stimuli must be spectrally identical, and this
is *not* metamerism.
Fred Bunting