Re: Neutral grey under different lighting
Re: Neutral grey under different lighting
- Subject: Re: Neutral grey under different lighting
- From: Roger Breton <email@hidden>
- Date: Sun, 09 Sep 2007 10:48:14 -0400
Marco,
> It would seem to me that if two colored objects match under all illuminants,
> they are very likely to match spectrally too, which also makes it highly
> likely that they are made from the same, or very similar, materials and
> pigments.
Well, I'm not so sure. I remember hearing about industrial color formulation
used in textile, for instance, where the choice of "ingredients" was such
that it minimized metamerism. So, I am tempted to hypothesize in view of my
limited knowledge that it's possible to have two color surfaces match under
a variety of light sources yet they don't exhibit the same spectral
reflectance.
To add to the discussion of metamerism, I seem to remember that true
metamers are those where their spectral curves intersect at least once -- or
twice? That's one sure way I always knew to tell a pair of metameric colors.
But of course, that can't apply to the case of a "single" color.
> I think that "color inconstancy" already properly conveys its full meaning
> (i.e., a failure in maintaining the color perceptually constant among
> different illuminants, once the human observer's eyes have undergone
> chromatic adaptation and discounted the illuminant).
>
> "Color inconstancy failure" would probably be redundant, in that light.
You're right. I was playing the devil's advocate -- enuff terminological
abuse.
> I think that Peter intends "device metamerism" to mean that two different
> cameras (or scanners, or what have you) will record and produce the same
> tristimulus values from two colored objects for which (under a given
> illuminant) a human observer will instead observe a metameric failure. Is
> that correct, Peter?
Makes sense to me ;-)
> Marco Ugolini
Best regards,
Roger Breton
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