Re: Just How Blind is the Human Race?
From: Christopher James Huff (cjameshuff_at_earthlink.net)
Date: 07/01/04
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Date: Thu, 01 Jul 2004 00:48:17 GMT
In article <40E114FE.F0DF15BC@arvig.net>,
"Dennis M. Hammes" <scrawlmark@arvig.net> wrote:
> Monochromatic-with-filters; or "quadrichromatic." But not "tri-."
> 11-cis retinal is the /only/ photosensor we've got.
> The three oil filters (assorted among the "cones") reduce the
> incident light level considerably, not the sensitivity.
> Same happens putting color filters on a camera or litho
> separations.
Trichromatic with additional luminance sensors...but still trichromatic.
Rod cells are not color sensors.
BTW, an occasional tetrachrome is possible: the genes for the green
pigment are carried on the X chromosome. Some women carry slightly
different versions on each X chromosome, giving them two types of green
cone cells with slightly different peak sensitivities. Last I heard,
only one person had been found with tetrachromatic vision.
> > The two sensors are so similar that the difference in sensitivity
> > at any given wavelength between red and green is quite small.
BTW, here's a graph of the sensitivities:
http://en.wikipedia.org/wiki/Cone_cell
Intermediate (green) and long (red) even share some odd little
irregularities in their curve shapes (over in the cyan-blue range). I
wonder how similar the dyes responsible are...but there is a clear
difference in which one is greater, over all but a narrow area of the
spectrum.
> Actually not; we are rather more sensitive to green by at least
> e=hf.
> Why subs and planes are set "cockpit red" at night.
Red makes the eye adapt very little...you can still see the cockpit
(though not as well as you could if it were lit in green), but it
doesn't ruin your night vision.
-- Christopher James Huff <cjameshuff@earthlink.net> http://home.earthlink.net/~cjameshuff/ POV-Ray TAG: <chris.huff@tag.povray.org> http://tag.povray.org/
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