"Bart van der Wolf" …
"PR" wrote in message
On Thu, 30 Oct 2003 20:55:42 +0000 (UTC), David Hitchin
wrote:
"Metamarism" is the undesirable property of some inks which makes them change colour under different lights. How is the word pronounced? meta – merism or metam -erism?
Don’t all printed colors change under different lighting?
Yes, but not as strong as these materials. A metamere is a color that looks the same as a spectrum color (e.g. yellow), but it is built from the combination of two (or more) different (red and green) colors, a compound. Both can look the same under a given illumination, but the different components change at a different rate and therefore the effect can be much stronger than on broad or single spectrum colors.
Bart
Bart,
metamers are spectra which cause the same tristimulus excitation for eye+brain. Has nothing to do with surfaces etc. The spectrum is already emitted light.
IMO, your explanation fails immediately for purple/magenta: there is no pure spectral magenta as a reference.
Metamerism:
a) the effect that different spectra cause the same perceptual impression.
b) the effect that a surface causes very different perceptual impressions
for different illuminants.
These are two DISTINCT definitions (R.W.G.Hunt, Measuring Colour) which are used both, though with different meanings.
The version b) doesn´t mean the effect by different (correlated) color temperatures. It means the interaction between "peaky" surface reflectances and "peaky" illuminant spectra.
Smooth spectra for different illuminants (e.g. D50, D65) don´t cause meta- merism. The shift is easily balanced by eye+brain by adaptation.
Offset prints don´t suffer from metamerism version b). But inkjet prints do, though the ink spectra (for single inks) are smooth. An explanation is not available, so far.
Best regards –Gernot Hoffmann