From: Paul Doherty (pauld@exploratorium.edu)
Date: Fri Jul 11 2003 - 18:20:40 PDT
Message-Id: <l03110746bb35105d68b8@[192.168.111.76]> Date: Fri, 11 Jul 2003 18:20:40 -0700 From: Paul Doherty <pauld@exploratorium.edu> Subject: Re: pinhole light and pigments
Hi Mark good questions
Well the "Blue" pigment is actually cyan pigment if it mixes with yellow to
make green.
Don't use light addition with pigments use light subtraction.
So yellow pigment removes blue light from white light leaving red and green
to reflect.
cyan pigment removes red light (reflecting green and blue light.)
When you combine pigments you combine their color removals so yellow and
cyan together remove Blue and Red from white leaving green
Consider the combination of yellow and blue pigments
yellow remove blue , blue removes red and green
so white minus red minus green minus blue is black.
yellow pigment and blue pigment add to make black (or gray)
>1) I assume that when two pigments mix they do not form a new compound. For
>example, blue paint and yellow paint will create green paint. The mixture
>(which is not a compound) still reflects blue light and yellow light and our
>eyes interpret these two frequencies as green. Is that right?
The leaf reflects a broad spectrum of light in the green range.
>
>2) Assuming the above description is correct: When I see a green leaf in
>nature am I seeing two frequencies at once (blue and yellow) or is the leaf
>reflecting a single frequency?
For example: blue and yellow pigments are complemetary colors
see above and note that blue pignment and yellow pigment add to black (AKA
gray)
>
>3) An acquantaince of mine is talking a lot about complimentary colors and
>the color wheel. What is the a physical basis of the fact that two color
>compliments will make "neutral grey"?
Paul d
>
>Mark Lawton
>Currently in Santa Fe studying classics
>
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