Metamerism vs Color Constancy - No! Again? [Was: To UV or not]
Metamerism vs Color Constancy - No! Again? [Was: To UV or not]
- Subject: Metamerism vs Color Constancy - No! Again? [Was: To UV or not]
- From: Marco Ugolini <email@hidden>
- Date: Thu, 21 Sep 2006 12:18:00 -0700
In a message dated 9/21/06 4:54 AM, Bret Hesler wrote:
> I am not a fan of the FWA-free papers, simply because the printing papers
> You may get a good match in one booth, but the paper with FWAs will shift
> color when you view it in the other booth. That is metamerism.
Sorry, but this is a pet peeve of mine, and I cannot be silent.
What you are referring to is more accurately labeled "color inconstancy," or
"color instability," because we have *one sample* exhibiting markedly
changing behaviors under different illuminants.
*Metamerism failure*, on the other hand, occurs when two *simultaneous*
units generate different perceptual results (2 prints made from different
devices and papers viewed under one illuminant; 2 identical prints viewed
under two separate illuminants next to one another; 2 observers looking at
the same color; 2 observers looking at the same color from different viewing
angles; etc.).
Notice the expression "metamerism failure": metamerism is a *positive*
quality, something we would rather have than not in most situations. It's
what allows us to see two colors as identical under certain illuminants,
though their spectral compositions may differ substantially.
Instead, in the color management community, we often hear "metamerism"
mentioned as that "terrible thing" that we must avoid at all costs: that is
a mistaken notion, though I once used to make the same mistake myself.
See this Wikipedia entry:
<http://en.wikipedia.org/wiki/Metamerism_(color)>
"The phenomenon of metamerism is sometimes confused with color constancy.
Metamerism occurs when the spectral attributes of the color stimulus are
different, but the perceived color is the same, when samples are viewed side
by side. Color constancy occurs when the perceived color is different, but
the color identity is the same, when an object is viewed in different
situations. That is, an observer is conscious that a lawn appears to be a
much brighter green under noon sunlight than near sunset, but recognizes the
color as "the same green" by taking into account the difference in viewing
situation."
Regards.
--------------
Marco Ugolini
Mill Valley, CA
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