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