Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!magnus.acs.ohio-state.edu!tut.cis.ohio-state.edu!ucbvax!dog.ee.lbl.gov!nosc!humu!pegasus!pinhead!todd
From: todd@pinhead.pegasus.com (Todd Ogasawara)
Newsgroups: sci.bio
Subject: Re: Primary colors in human color vision
Message-ID: <1991Mar23.193006.22992@pinhead.pegasus.com>
Date: 23 Mar 91 19:30:06 GMT
References: <00945FE5.1F9B5480@aclcb.purdue.edu>
Organization: Hawaii Medical Service Association
Lines: 35

In article <00945FE5.1F9B5480@aclcb.purdue.edu> miguel@aclcb.purdue.edu (Phillip) writes:
>   The additive primary hues, according to an undergrad general psychology 
>text book I have (Gleitmann (sp?)), are blue and yellow (which are 
>complementary) and red and green (complementary).  Blue, yellow and green 
>all have a "unique" wavelength at which the human eye/brain percieves them 
[...]
>grey (i.e. blue + yellow = grey).  The process is called "opponent-pair" or 
[...]
>    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.

I'm not familiar with the text you mention. However, I suspect you may have
missed a few pages. The processing of color in human vision occurs at
several levels. The level you mention (opponent pair stuff) occurs further
down the processing chain.

The processing of primary colors occurs at the retinal level (you might
want to read Boynton's "Human Color Vision" to get the full biochemistry of
this process) in sensory cells called the cones which fire optimally when
absorbing wavelengths which we call red, green, and blue (RGB). There are
also retinal cells called rods which play a primary role in night vision.

Human color vision is, of course, much more complex than simply the two
levels mentioned so far (retinal and bipolar cells). The Land effect
certainly seems to indicate that their are higher cognitive factors that
come into play. The perception of "brown" which appears to require a
contrasting surround to occur is another indication of other higher
processing. It has been years since I've looked at the literature though.
So, if anyone else has more recent info to chime in with, I'd be interested
to read it.
-- 
Todd Ogasawara ::: Hawaii Medical Service Association
Internet       ::: todd@pinhead.pegasus.com
Telephone      ::: (808) 536-9162 ext. 7