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From: fwb@demon.siemens.com (Frederic W. Brehm)
Newsgroups: sci.electronics,rec.audio
Subject: Re: Looking for Blue LEDs
Keywords: blue blue blue, not yellow or red or green
Message-ID: <2214@siemens.UUCP>
Date: 23 Sep 88 17:48:01 GMT
References: <1138@nmtsun.nmt.edu> <862@ritcv.UUCP> <255@rna.UUCP> <4422@lynx.UUCP> <871@ritcv.UUCP>
Sender: news@siemens.UUCP
Reply-To: fwb@demon.UUCP (Frederic W. Brehm)
Organization: Siemens Research and Technology Laboratories
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In article <871@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes:
>
>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?

I thought that red, yellow and blue were the "primary" colors until I took
Physics II in high school.  Don't believe everything you learned in
elementary school.

Red, green and blue are the ADDITIVE primary colors.  That means that you
add different proportions of these three to make all of the different
colors.  Color CRT screens and the projection TVs add the light from the
different phosphors to produce color.

The SUBTRACTIVE primaries are cyan (kind of blueish-green), magenta (kind
of reddish-purple), and yellow.  This means that you subtract different
proportions of these three from white light to produce all the different
colors.  Printing technologies use this method.

There is a color wheel which describes the relationships between the
additive and subtractive primaries.  You can probably find it in a good
book on color photography.

Fred
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