Re: Another quote from Roy Berns on metamerism-color inconstancy
Re: Another quote from Roy Berns on metamerism-color inconstancy
- Subject: Re: Another quote from Roy Berns on metamerism-color inconstancy
- From: Ernst Dinkla <email@hidden>
- Date: Thu, 17 Jun 2010 22:56:35 +0200
Marco Ugolini schreef:
This is from the same book ("Billmeyer and Saltzman's Principles of Color
Technology", Third Edition, Wiley & Sons, 2000), on page 130:
"[W]e want to stress that color inconstancy applies to a SINGLE SAMPLE
[author's emphasis -- MU] viewed under multiple illuminants. 'Metamerism'
should never be used when describing a single sample's change in color due
to changes in illumination. Metamerism always describes the color
relationship between a PAIR OF SAMPLES [author's emphasis -- MU], at
minimum."
Like I said earlier, there's little to add to this one either. Couldn't be
clearer and more straightforward.
But of course anyone is free to ignore it.
Marco Ugolini
A complex one then. Not two or more samples of the same color and not
one sample either. A range of monochromes along the same hue angle on
one page. Let us say a greyscale range. A neutral black and white print.
Viewed under a continous spectrum D50 lightsource and doesn't show color
shifts along the range and no tone fluctuations either. Goes wrong under
a bad CFL lamp, green in the highlights, bluish halfway, red shift
towards black. There is a reference as we expect a neutral grey or at
least a continuous hue along that tone range, no hue differences, no
saturation differences. Only the grey value variation. In fact some
metamerism tests are made that way, black and white line grid grey next
to for example a composite mix grey. Right, the samples have the same
grey value then when it gives the metameric match. Nevertheless there's
a good reason why we discriminate the shifts in B&W prints where it
wouldn't be as easy in color prints. This comes close to a metameric
match or failure in my opinion.
A good friend, artist in his early years, made (40 years ago) some
landscape paintings from sketches where the tone values and saturation
where kept equal in all patches, only the hues varied. Munsell color
system book next to the easel. I recall the gouache paint was mixed
under a fluorescent lamp, probably the Philips 95 then, in best case. I
don't think we ever discussed metamerism then but I'm sure that painting
would show unexpected tone and saturation shifts when viewed outside,
and very visible. Something similar would happen if only saturation
varied in an image under one light source and hue and grey value were equal.
--
Met vriendelijke groeten, Ernst
Dinkla Gallery Canvas Wrap Actions
| Dinkla Grafische Techniek |
| www.pigment-print.com |
| ( unvollendet ) |
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