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Re: Color



Popular reference to Edwin H.Land's work on color vision

"Experiments in color vision", Edwin H. Land, Scientific American,
May, 1959, vol.200, No.5, pp 84-99.

Offprint is also available.
Scientific American Offprint 223, W.H.Freeman( I think I got it right).

It is also available in the two volumes of selected offprints in
Physical Sciences published by Freeman.

regards,

Sarma.

On 2 Nov 2000, at 17:51, John M. Clement wrote:

One of the problems of color perception comes from the extremely large amount of processing done immediately after the retina. This is evident in the fact that a color swatch is usually perceived as having the same color under varying light condition. Edwin Land came up with an interesting
explanation for this that he called the "Retinex theory". This particular theory was presented at an APS meeting in either the late 60s or early 70s. He presented the audience with a series of color swatches, and then illuminated both ends of the swatches with different ratios of blue and red
light. At one end a red swatch had exactly the same ratio of blue and red light as a blue swatch at the other end. Each retained its color. Essentially he proposed that color perception relied on comparison across boundaries. His theory is still around, and aspects of it have been
incorporated into other theories.

There is a very good web site that covers all of the senses at http://www.hhmi.org/senses/ This is suitable for HS students.

Another interesting effect is the color stereo effect. This is the effect of perceiving different colors at different distances from the observer. You can see this by looking at contrasting colors next to each other and then by blocking the outer edge of your eyes with both hands. It is
caused by refraction which causes different colors to focus on different planes. You can also exaggerate this effect by using prismatic glasses. Some research has found that some color blind people can gain good perception of color by using such glasses. Incidentally some people without depth
perception can also gain depth perception by looking through high quality stereo viewers or at the 3-D Imax. One friend immediately became a 3-d photographer the first time he could see 3-D in a Realist viewer.

Of course all of this has not solved the problem of whether white is a color. Unfortunately many teachers use that question on a test to find out which students have memorized the "right" answer. Since it is a matter of perspective, a good teacher would use this as an opportunity for
discussion, and would grade the question on the basis of good logical argument. My preferred color of chocolate is dark not white!

John M. Clement