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: Mon, 18 Jun 2001 16:36:47 -0500
>
> If this second case is not "metamerism" - what is it an example of?
>
>
This is an example of "color inconstancy". As you noticed, the current
>
standarized definitions of metamerism require a pair of samples.
The distinction is so subtle that reminds one of a lawyer hanging to the
letter of the law instead of the law itself.
But the most important part is that "metamerism", by defining a
comparison between two samples, doesn't delve into the detail of which of
the samples is the culprit. Or more properly said, both are, because
sample "a"(the stable one) can be accused of not shifting color as sample
"b"(the unstable one) does. Or viceversa, make sample "b", the one that
shifts when "a" doesn't, the culprit of metamerism.
So it's a matter of which sample you consider your reference. Every print
changes a lot under different lights. But you consider your "reference"
as if it were not changing, and speak about the proof "shifting". This is
not true. Both are shifting, just differently.
Imagine for a moment JCPenney prints the thousands of its catalogs on
Epson printers. And then we've got an offset press as a proofer, and try
to match what the final products will be. We do our stuff and get the
match. Then we move to a different light, and the match is no longer.
Do we say our offset proof is "metameric"? Hell, it doesn't match the
final product...
When evaluating a single sample, how would you relate to metamerism? you
would have to introduce an imaginary "stable sample" that in fact is
being played by your memory, which supposedly doesn't shift colors under
different lights. And that imaginary sample, coupled with the real one,
would form a "metameric pair".
The problem is, "stable sample" doesn't exist, not even in your
imagination. Color perception is so complex that chromatic & lightness
adaptation could well be taking place in stored memories! doesn't seem
unreasonable at all.
What you perceive is a compound of many physiological and psychological
things, and I believe the part played by the actual stimulus reaching
your photoreceptor cells is astoundingly smaller than most of us think.
So I would rather think of a color shift as something very relative. Kind
of "a shift different from the one your brain is expecting and
compensating for".
Wow, this post is beating the record for aimless anarchist rants! What do
we do now? :)
best regards,
-- Roberto Michelena
EOS S.A.
Lima, Peru