On monochrome images and metamerism, or not.
On monochrome images and metamerism, or not.
- Subject: On monochrome images and metamerism, or not.
- From: Ernst Dinkla <email@hidden>
- Date: Sat, 19 Jun 2010 17:07:42 +0200
What is it that makes the unexpected color shift in B&W images between a
D50 viewing light and daylight more distinct compared to the color print
from the same printer model? Specifically the hue shifts over the tone
range. Assuming that the B&W print gives a very even hue impression
under D50 light over the tone range.
Is it based on a "virtual" expectation of what a greyscale image should
be or do we have some reference in the image itself that marks the
shifts? Is the explanation that in a color print small color shifts go
unnoticed not related to the fact that there are too many variables in
the print to create a reference for unexpected shifts in other parts of
the image? The adaption of the eye and brain to different light sources
covering up unexpected shifts in the color print but not in the
monochrome print as there is some reference left in the other monochrome
tone?
I think it is that reference to the rest of the print, a kind of mean
values of hue and saturation, that let us decide whether we think the
tone ranges match or fail on hue and saturation. A shift in tone/value
in the same light chance probably going unnoticed as a reference for that
isn't present. That is different to the metameric match/failure with
two or more samples. In the metameric match the two samples give equal
stimuli on the 3 values and they can differ on the 3 values in a
metameric failure. The reference to one another makes it possible to say
on what of the 3 values they differ. At the same time making that
condition of two samples necessary.
I wouldn't mind if someone says that the tone range of a single B&W
print under D50 makes a good metameric match or metameric failure and
adds "I mean on hue and saturation". It may not be written in the books
like that but I guess that the researchers were not unaware of the
relation between the phenomena either.
I'm using the HSV model here as I find that the easiest to describe it
with. I'm sure there is a better color perception model possible but
that doesn't change the idea behind it.
--
Met vriendelijke groeten, Ernst
Dinkla Gallery Canvas Wrap Actions
| Dinkla Grafische Techniek |
| www.pigment-print.com |
| ( unvollendet ) |
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