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HYB:colors [was:Re: layers]


Darm, the problem of colors isn't in the iris (plant, flower)--it is in how
colors are recorded and processed by our internal receptors and biological
"computers" (speaking in analogical terms).

When a full, balanced spectrum of visible light enters the eye it is brought
into focus on the retina.

Two basically different forms of receptor cells (the same notion as a
microphone is to sound) are present.  Rods do not pick up color, merely light
vs. dark, and make us sensitive to very low levels of illumination at night,
or sensitive to motion in extreme peripheral vision.  An image of a preditor
or enemy moving at the extreme edge of our visual field causes an instant
surge of adrenaline, and a startle, defensive reaction.

On the other hand, cones pick up two basic pieces of information.  Just how
this works is over my head, but relatively much higher numbers of photons are
required to "fire" the data stream (nerve impulse) than with rods.  Thus we
are able to tolerate bright daylight and see images in detail and in color,
especially in the core of our visual field--on the retina this is called the
"macula," an area packed especially densely with cones.

The information is split into two sets.  One is fired off by <either> blue or
yellow, and the other <either> by red or green.  (This is why Daltonism, a
form of color blindness, only affects the ability to differentiate between
green and red.  Another form of color-blindness exists for the blue-yellow
pair, but is extremely rare).

Back about halfway, above the ear, and deep inside, there is a switching
station for vision that sorts both sets of impulses into blue-OR-yellow,
red-OR-green, then the data is sent on back to the cortex where the image from
the two eyes is processed, compared.

This is why a TV can have only three colors of dots, or an LCD color screen on
a computer monitor have only the same three, from which we perceive a full
spectrum, but only receive three fuzzily-discrete wavelengths.

We do <not> see a continuous spectrum.  What we see is a set of ranges of
wavelengths varying in probability of firing the nerve impulse.  These ranges
over-lap, but the result is we see green to orange-yellow colors as much
brighter than either red or blue bordering on indigo, when they are
(objectively measured) of equal intensity, because that middle part of the
color range fires <both> red-green and blue-yellow. nerve impulses.

This is what makes additive and subtractive color mixes--additive, such as
projection style TV monster-sized screens, which have three color images
projecting at the screen, usually from behind, or substractive, such as those
where blue-plus-yellow makes green--so important.  In additive mix, blue plus
yellow makes white, not green.

All of this is counter-intuitive, I know.  But read about it--you may find it
fascinating.  I did!

Neil Mogensen  z 7 western NC mountains

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