Re: photogravures
Re: photogravures
- Subject: Re: photogravures
- From: email@hidden (Bruce Fraser)
- Date: Wed, 24 Oct 2001 15:03:59 -0700
At 2:44 AM -0700 10/24/01, Wire Moore wrote:
on 10/24/01 12:06 AM, David Wollmann at email@hidden wrote:
Tom Lianza writes:
There seems to a consistent misunderstanding about metamerism that seems to
run through the ink jet industry and then get reinforced by some
contributers to this group.
Curious, is there another word then that can be assigned to
this? I noticed in C. David Tobie's response to my original
post that he was putting "metamerism" in quotes, and from his
other comments gathered that what I'm seeing does not fully
meet the definition.
I've looked into this a bit. What I've found is that the word metamerism is
gaining popularity among digital imaging users, especially inkjet-printer
cognoscenti, to mean pretty close to the opposite to what it means in terms
of color theory.
WRT color theory, metamerism refers to metameric matches and metameric
pairs: A metameric match is the case of colored objects that appear to match
only under certain lighting conditions. A metameric pair is the case of two
illuminants with different spectra that appear the same. A somewhat more
general definition is the quality of color stimuli with differing spectral
power distributions having matching appearance.
WRT digital imaging, metamerism is a more of a meme. Inkjet printers
commonly produce prints that appear different depending on lighting
conditions. It's more of a problem for some printing systems than others.
Differences that are egregious, or which seem wildly unexpected or
unpredictable, especially such that may jeopardize business relationships,
are popular topics of conversation among inkjet printer users, and they
typically say metamerism to convey the general case of conditions or results
whereby a metameric match is desired or expected, but not obtained. This is
a mouthful, and there aren't any other strong candidates for a term, so I
can see why folks have taken to saying metamerism for short.
If your on-screen image is one sample, your inkjet print is the
second sample, and they match under one lighting condition but not
another, then you have a metameric pair -- a pure example of
metamerism with no quotes required.
When you're comparing the print under one lighting condition to the
print under another, it's more questionable as to whether you're
dealing with two samples (though certainly both the spectral response
curve and the tristimulus values will be different for the two
conditions), hence the quotes.
But in either case, it's the property of eyes that allows two
different spectra to create the same color appearance that lies at
the heart of the problem. The metamerism part of the equation is that
under some lighting condition, the print has the desired appearance.
Most of the discussion has centered around metamerism as a problem.
It's worth bearing in mind that metamerism is what allows us to
create color matches using primary colors in the first place.
Bruce
--
email@hidden