Taking a print and having it appear differently when moved under a different illuminants wouldn’t be metamerism and think the term Ernst is referring to in this example is color inconsistency. Metameric failure would be accepted by some as well.
Some color gurus on another list became quite aggressive in their messages when "metamerism" was used loosely.. So I started to describe it as "color inconstancy to different light sources". Which is the formulation that covers the practice of taking just one sample/print from one light to the other by one observer. As it will not be understood by the common print maker I add "metamerism" next to it on other lists. Would an abbreviation like CI*^ be short enough for the lazy ones and suggest "authority" on the subject ? I think the term "metamerism" has those qualities so will be hard to get rid off.
With a B&W print (= varying value/tone, same hue, same chroma/saturation) I think that there is a condition that comes close to the "two (or more) samples matching to one light source for one observer", or "two (or more) samples not matching to one light source for one observer", which is roughly what metameric match, metameric failure to light, stand for. That point of view was supported by some (actually off line, with references to research done) in the discussion that became so aggressive. The fact that a color deviation is much easier to see in B&W prints than the same deviation is in color prints is a sign that our eyes have a reference in B&W prints that they do not have in color prints. Which is getting close to the metameric conditions. Print areas that only differ on value/tone are a good reference. An overall color shift will not be so easily discriminated but one tone range deviating in hue from the rest will be seen immediately. The same can be seen in pictures where only the hue varies or where only the saturation varies. Odd ones, I know but a good friend made some 40 years ago (Munsell book next to the easel) so I was familiar with them before they became available with a few steps in Photoshop.
met vriendelijke groeten, Ernst
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