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From: john@frog.UUCP (John Woods, Software)
Newsgroups: comp.graphics
Subject: Re: Frequency distributions of red, green, and blue.
Message-ID: <1130@frog.UUCP>
Date: Sun, 16-Nov-86 19:40:57 EST
Article-I.D.: frog.1130
Posted: Sun Nov 16 19:40:57 1986
Date-Received: Mon, 17-Nov-86 05:43:19 EST
References: <647@husc6.HARVARD.EDU> <2843@clyde.ATT.COM>
Organization: Superfrog Heaven [ CRDS, Framingham MA ]
Lines: 31

>From clyde!rutgers!seismo!husc6!endor!greg Fri Nov 14 09:58:22 EST 1986
>>Does anyone have know (or have references to) the exact frequency profiles
>>of red, green, and blue phosphorous on a color monitor, red, green, and blue
>>film, and the red, green, and blue receptors in a person's eye?
>>Greg
> >
> You've fallen into a trap common to computer technologists and
> engineers: you've assumed that the eye and brain work like a computer.
> The cones in the eye's retina respond differentially to frequency
> of the incoming radiation.

First, the cones individually do respond to particular bands of light
preferentially (see articles in the past few months in SCIENCE and Scientific
American), roughly centering on "red", "blue", and "green".

However, perceiving color IS done differentially, and in Freshman Physics at
MIT, we learned about this (I believe it was discovered by Edwin Land), and
were given a demonstration:  a black and white picture of a clown with
brightly colored candy, taken with a blue filter, and the same picture taken
without a filter (and, due to the characteristics of the film, having the
strongest color sensitivity in the yellow area spectrum).  When these two
images were projected onto the screen, we saw full color (reds, greens, you
name it), even though these colors weren't in either slide.  It was stated
(without demonstration) that you can get the same effect by making photos
using the two yellow lines of sodium -- that tiny difference in frequency
allows the brain to reconstruct the color of the actual image!

--
John Woods, Charles River Data Systems, Framingham MA, (617) 626-1101
...!decvax!frog!john, ...!mit-eddie!jfw, jfw%mit-ccc@MIT-XX.ARPA

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