Re: =Color constancy and metamerism
Re: =Color constancy and metamerism
- Subject: Re: =Color constancy and metamerism
- From: Marco Ugolini <email@hidden>
- Date: Tue, 20 Sep 2005 15:49:52 -0700
In a message dated Tue, 20 Sep 2005 16:53:52, Mark Rice wrote:
> I don't think so - metamerism can occur with a single sample.
OK. Let's see.
> But seriously, the prime example that Mees used of metamerism is the olive
> dress example. This discussion did not involve the usual pair of object -
> no, I take that back. The pair of objects was the original green dress and
> the photo of the dress. The dress appears green to the eye, but it appears
> brown on the film. This occurs because the spectral response curves of the
> average eye (different peoples eyes can see different objects as different
> colors too, of course - color blindness is an extreme example) don't match
> the spectral response curves of the film, or of the digital chip. Mees used
> this a primary example of metamerism, and it is a very common problem for
> photographers, especially when photographing fabrics.
This mismatch between the actual dress and its photographic image clearly
does involve TWO SAMPLES, but also TWO ILLUMINANTS (the ambient light
falling on the dress, and the light from the light box upon which one places
the reversal film). Strictly speaking, one is comparing two spectrally
different samples separately, each under a different illuminant.
If a metameric match is supposed to occur between two samples under the SAME
illuminant, then is this example of the green dress truly an instance of
metamerism? I understand very well the problem that Mees was describing,
having been a photographer myself. But to put it under the rubric of
metamerism may be a bit of a stretch (though we understand what he means).
Perhaps if we compared a PRINT of the dress with the dress itself under the
same illuminant, that would be a more germane way to establish a metameric
match, or mismatch.
> Well! My wife always tells me that if she asks me for the time, I tell her
> how to build a watch, and then throw in the history of Switzerland as well.
> Sorry if I rambled.
Man, I'm not going to ask YOU the time... just kidding. Ciao.
--------------
Marco Ugolini
Mill Valley, CA
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