[Neuroscience] Re: Color and Vision

mimo_545 at hotmail.com mimo_545 at hotmail.com
Fri Aug 11 18:38:10 EST 2006


zaphod at myrealbox.com wrote:
>Hi:
>In writing about Technicolor for my next book on cinema I've become
>interested in how people see color.  I'm trying to figure out, first,
>what it meant to leave out blue in the first experiments with 2-strip
>Technicolor,

(try Edwin Land?)

>and, second, what the thinking was in choosing the final
>colors in 3-strip contemporary) Technicolor.  I've gone through a few
>introductory and college texts (for example Gordon, *Theories of Visual
>Perception*), but, either because I haven't understood the
>explanations or because I haven't read sufficiently specific texts, I
>still have at least two questions left.  These are:

Have you tried posting this in;
rec.arts.movies-production,alt.movies.visual-effects ?

perception of mixing colored light is different from mixed
colored pigments. Mixing all wavelengths of light results in
white light, mixing pigments together results in darker tones.
Color perception via cones and rods work a bit like switches
and the impulses are further mediated by other cells.
(theres loads on the net, I use Levine & Shefners'Fundamentals
of Sensation & perception'Oxford)

>     1. Do all people's cones register the same three sets of light
>frequencies, or do people register even slightly different frequencies
>(hues?) of blue, red, and green?  In other words, is the optimal
>frequency in nanometers of light absorbed by the three different cones
>the same across all human beings (appr. 445nm, 535nm, and 575nm)?

No, people vary, eg some people are extra sensitive to red
wavelengths others have no color vision. Those who are especially
sensitive to color (cones)often have less sensitivity in low light,
while colorblindness frequently means extra sensitivity at
very low light levels (rods).

>     2. To what degree are primary colors really "primary"?  In
>other words, to what degree do they correctly refer to the way in which
>the three different cones reflect light?  Is it safe to say, for
>example, that some degree of subjectivity exists in assigning red,
>yellow, and blue (or red, green, and blue; CYM, etc.) as primary
>colors?

Yes. There is a degree of subjectivity.
but you can sort that out with a sheet of graph paper and
a calculator! If its a low light level, and you can't
pick up a red, often means that you're also too far away,
+ if you're very familiar with your target you'll automatically
assign a color to it. some colors can be guessed, ie, watching
billiards/pool in monochrome TV we assign colors to the balls
because the desaturated cols would also appear to have a
monochromatic value, but only when you see them amongst
the others on the table etc.

>Thank you.

no problem, but I'd like to read what the experts have to say as
well.
N.



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