Re: FWD (SK) Re: The night side of science

From: Mike Lorrey (mlorrey@datamann.com)
Date: Mon Aug 20 2001 - 09:00:51 MDT


Louis Newstrom wrote:
>
> From: "Mike Lorrey" <mlorrey@datamann.com>
> > What we don't know is whether Newton was or was not one of those rare
> > people with four types of color cones in their retinas. If he was, this
> > could explain the seven color statement.
>
> Probably not. People who can detect four colors (called "tetrachromates")
> see two shades of what we would call "green" (near the middle of the
> spectrum).
>
> I think it is more probable that he called cyan "blue" (like the sky) and
> then called the darker pure blue "indigo".

These are not mutually exclusive. Cones are not just sensitive in
specific wavelengths, they have bell curve sensitivity ranges that
extend far outside their areas of peak sensitivity, and the addition of
an additional cone type would create entirely different perceptions of
color gradients.

Deer, for example, have only blue and yellow cones, yet they are not
blind to wavelengths in between, they simply see them as various blue
and yellow shades of gray, and they also see deep into the ultraviolet
with their blue cones, which makes the industrial brightening dyes in
much human clothing and clothing detergents to stand out like neon
lights. They see reds and oranges as simply shades of yellow that blend
into the natural yellow background of nature (which is why wearing blaze
orange is better than wearing jeans when hunting).

Deer cannot, for instance, see green simply because they do not have red
cones. Green to them is just a shade of gray. Similarly, being a
tetrachromate would allow not only more ultraviolet sensitivity (which
is what I've read is a reported phenomenon of tetrachromates) but would
provide the person with greater sensitivity to more normal color
gradients as well.

You can, for instance, simulate deer sight with your computer monitor by
turning down to zero its red sensitivity.



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