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From: jsgray@watrose.UUCP
Newsgroups: comp.graphics
Subject: Re: Colour vision
Message-ID: <8562@watrose.UUCP>
Date: Thu, 12-Mar-87 08:40:30 EST
Article-I.D.: watrose.8562
Posted: Thu Mar 12 08:40:30 1987
Date-Received: Fri, 13-Mar-87 04:09:46 EST
References: <505@ubu.warwick.UUCP>
Reply-To: jsgray@watrose.UUCP (Jan Gray)
Organization: University of Waterloo
Lines: 25
Keywords: metamerism

When you perceive the same colour from a monochromatic yellow light
and from an image on your television set, you are experiencing the
phenomenon known as metamerism.

The eye has three different types of colour detecting cones.  These cones
each respond to a wide spectrum of colour, with maximum response situated
at a certain red, green, and blue wavelength.

When you irradiate these cones with a monochromatic yellow light,
the red and green cones are stimulated, but the blue cones (whose
spectral response is small or none for that yellow light) are not.
You perceive "yellow".

When you simularly irradiate these same cones simultaneously with the
red and green light from the phosphors on your television screen,
the red and green cones are stimulated, but the blue cones are not.
You perceive the same "yellow".

Thus it is quite possible to perceive the same colour from very
different spectral distributions (which are called metamers).


[I hope the colour experts here at UW will forgive my transgressions.]

Jan Gray    jsgray@watrose    University of Waterloo    (519) 885-1211 x3870