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Only 3 colours?

Neil neil_delver at hotmail.com
Fri Mar 22 21:01:58 EST 2002

"Danny Rich" <DannyRich at nospam.softhome.net> wrote in message
news:nyQm8.47856$bj1.16040390 at news02.optonline.net...
> "Bob May" <bobmay at nethere.com> wrote in message
> news:u9naqk166krr35 at corp.supernews.com...
> > Actually the reason for the red, green and blue is that these
are the
> colors
> > that the eye responds to with each of it's color detectors.  The
> > (along with parts in the eye) does the rest of the color
> > The real problem is to make a yellow line with nothing but the
red and
> green
> > lights so that a spectrometer will see it as yellow and not a
mix of red
> and
> > green.
> >
> > --
> > Bob May
> > Imagine the terrorist's fun when they realize that their 72
> virgins"
> > are all lesbians and cranky from it being that time of the
Is that who the lady bombers get?
> >
> This is the Thomas Young theory of vision which is only partly
true.  Since
> a spectrometer cannot "see" color getting a red and green to mix
to a single
> yellow line.  On the other hand, that is exactly the principle of
the Nagel
> anomoloscope - the only fool proof way to assess color blindness.
If you go
> to the Univ Cal San Diego color vision web site you will find
plots of the
> Long, Middle and Short wavelength sensitve cones and see that
their spectral
> sensitivity covers most of visible wavelength and are not Red,
Green & Blue
> sensitive - which is why color vision scientists label them L M S
instead of
> R G B.  So - Young was only partially right and in fact, Herring
who first
> postulated the opponent structure and Leo Hurvich and Dorthea
Jameson of the
> Univ. of Pennsylvania who first measured the opponent processes
were also
> only partly correct.  So, it is now generally accepted that post
> processing before the LGN results the addition of  some signals
> subtraction of others to form a polarized neural signal where Red
is traded
> off against Green and Yellow is traded off against Blue and Bright
is traded
> off against Dark  For a clearer description  I recommend the text
> Vision by Boynton and Kaiser published by the Optical Society of
> Danny Rich

The point I want to make is how interesting it is that we experience
those "fundamental looking" colors, which don't "appear" mixed with
something else. That is what the names really refer to, and they
presumable would come from stimulating only that one cone type - so
it seems the old names were right after all in the sense that
counts. Indeed, from that point of view, we really have four primary
colors since yellow doesn't look like it's made of red and green -
we don't call any colors "reddish-green" etc. (This point was noted
by the philosopher Wittgenstein, who unfortunately was too wrapped
up in the language principle per se to think of the interesting
point about the possible mechanism, given that only three colors are
needed to actually *make* the others.) These are fundamental codings
in our brain/minds, and it is interesting why red + green makes
something that doesn't look like a mixture, while the other
primaries do. It seems that our distant ape ancestors needed to make
fine distinctions between reds and greens and yellows in order to
pick properly ripe fruit. We are on the verge of being tetrachromats
who actually could add an extra cone type to see yellow separately -
not reproducible by mixing red and green light, not just looking
separate. There may be such a woman in France - search Google for
key words. Indeed, a very interesting article (3/02) about color in
Natural History, make the following observation; here roughly
remembered: Think of how curious it is that our appreciation of the
wonderful paintings in art museums is based on our primate
ancestors' need to distinguish ripe bananas.

Neil Bates

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