Xref: utzoo sci.electronics:3889 rec.audio:8433
Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!decwrl!ucbvax!ulysses!ggs
From: ggs@ulysses.homer.nj.att.com (Griff Smith)
Newsgroups: sci.electronics,rec.audio
Subject: Re: Looking for Blue LEDs
Summary: you're out
Keywords: blue blue blue, not yellow or red or green
Message-ID: <10635@ulysses.homer.nj.att.com>
Date: 23 Sep 88 12:37:12 GMT
References: <1138@nmtsun.nmt.edu> <862@ritcv.UUCP> <255@rna.UUCP> <4422@lynx.UUCP> <871@ritcv.UUCP>
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 37

In article <871@ritcv.UUCP>, cep4478@ritcv.UUCP (Christopher E. Piggott) writes:
> 
> ... (I learned a neat lesson this week - if
> you're not sure, SHUT UP ... some advice from me to myself).

Strike one.

> Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of
> the primary colors (being a combination of blue and yellow)?  Why shouldn't
> it be red, YELLOW, blue?

This should be in rec.video or rec.photo.  Strike two.

You're wrong.  Strike three.

Red, green and blue are ADDITIVE primaries; combine light sources that
radiate the three primaries and get white.  Yellow, cyan and magenta
are subtractive primaries; cyan subtracts red, magenta subtracts green,
yellow subtracts blue.  Mix the three subtractive primary dyes and they
subtract the three additive primary colors to make black.

The sensation of yellow is the result of stimulating the red and green
sensitive cells in the retina.  A pure yellow light source has this
effect because the sensitivity curves for the two cell types overlap
strongly in that part of the spectrum.  If you bother to look closely
at a color television you will see that the red and green phosphors are
`on' when the image is yellow.  Green can be made by mixing a cyan
(blue-green) dye with a yellow (red-green) dye.  Cyan subtracts red,
yellow subtracts blue; green remains.

Please don't bring up two-color primary theories, I know about them.
Now, can we get back to the DSP lessons?
-- 
Griff Smith	AT&T (Bell Laboratories), Murray Hill
Phone:		1-201-582-7736
UUCP:		{most AT&T sites}!ulysses!ggs
Internet:	ggs@ulysses.att.com