Re: Neutral grey under different lighting
Re: Neutral grey under different lighting
- Subject: Re: Neutral grey under different lighting
- From: Graeme Gill <email@hidden>
- Date: Mon, 10 Sep 2007 17:37:03 +1000
Marco Ugolini wrote:
In a message dated 9/4/07 8:17 AM, Fleisher, Ken wrote:
You cannot have two illuminants that are metamers.
> Correct. You must have an observer, an object (two objects, in metameric
> matches) and an illuminant in each case. None of these three elements
> suffices in isolation.
Incorrect. Illuminants are just sources of spectral radiation.
If two light sources appear to be the same color but are composed
of different spectrums, then they are a metameric pair. This is exactly
the same thing as a metameric match between samples on two different
display devices, say an LCD and a CRT, or a CRT and a print under a given
illumination. All tri-stimulus color reproduction (whether emissive or
reflective) is based on metamerism. The standard observer is based on
making metameric matches between light sources.
Right. But saying that a pair is metameric, and not specifying *exactly
which* illuminant is needed to effect a match, is confusing. Specially if,
at the time that this description of them as a metameric pair is being
offered, they are being viewed with an illuminant under which they do *not*
match.
You're leading yourselves right up the garden path in following the idea
that metamerism is something intrinsically tied to reflective samples.
Graeme Gill.
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