Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!psuvax1!psuvm!jms111
Organization: Penn State University
Date: Saturday, 23 Mar 1991 01:59:22 EST
From: Jenni Sheehey <JMS111@psuvm.psu.edu>
Message-ID: <91082.015922JMS111@psuvm.psu.edu>
Newsgroups: sci.bio
Subject: Re: Primary colors in human color vision
References:  <00945FE5.1F9B5480@aclcb.purdue.edu>

In article <00945FE5.1F9B5480@aclcb.purdue.edu>, miguel@aclcb.purdue.edu
(Phillip) says:
>
>   The additive primary hues, according to an undergrad general psychology
>text book I have (Gleitmann (sp?)), are blue and yellow (which are

Great text book.  I love it.  =)

>    So how does a color TV work?  I understand that it uses only red green
>and blue and that red and green mixed together (and surely this would be an
>additive process, not a subtractive one) produce yellow.
>    Does anyone know?

This isn't my strong point, but I think I see where the confusion comes
from.  Additive mixing refers to light.  Subtractive mixing refers to
pigment/crayons/what have you.  The additive primaries are red, blue, and
green, while the subtractive primaries are red, blue, and yellow.
The reason that the two type are named that way (I suppose) is that
you are adding or subtracting the wavelengths  that are being absorbed.


The blue/yellow and red/green dichotomies are actually a facet of *vision*
rather than light, referring to the two types of cones present in the
retina.  (That's why a person who is red/green colorblind can often still
see blue, etc.)

Anyway, the end result of all this is that TV works additively, with the
blue and green light combining to form yellow.

Disclaimer: All I have is a BA in Psych, and a bit of experience tutoring
a course taught from the Gleitman, I'm not a PhD (like anyone would
mistake me for one--ha ha) =).  Besides, I bet even PhD's are wrong
every once in a while.  =)
                                            --Jenni
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