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Physical parameters define colors like the pigment primaries

  1. Nov 14, 2005 #1
    What physical parameters define colors like the pigment primaries - red, blue and yellow - and their mixtures? How about light primaries?
  2. jcsd
  3. Nov 14, 2005 #2


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    What do you mean by physical parameters? The wavelength of light determines its colour, but I guess you already knew that. As for pigments, if you mean, what property of a substance determines its colour, then I guess that has to do with atomic structure or is quantum mechanical. Primary pigments absorb one of the primary colours (wavelengths) and reflect the others.
  4. Nov 14, 2005 #3
    My question is basically: what frequencies are assigned to which primary colors, and what is the mechanism that would describe secondary colors as primary combinations corresponding to single frequencies?
  5. Nov 15, 2005 #4
    Just look up the EM wavelength chart. Different colors are at different wavelengths.
  6. Nov 15, 2005 #5
    That chart is more qualitative than physical regarding a precise definition for primary and secondary colors. Please refer to my previous post. E. g., what is the exact frequency or range of frequencies for the color blue, and how is green defined as a mixture of yellow and blue frequencies?
  7. Nov 15, 2005 #6
    You perceive Yellow & Blue as green but it's not really green. Its all about how your eye and brain perceives colors, your eye can't distinguish between real green light and the mixture of yellow and blue. A very interesting question you can ask is if you have a yellow and blue dot seperated by a distance x , how far away do you have to be to see green? For the color/wavelengths I will again refer you to a EM chart, it's out there.
  8. Nov 16, 2005 #7
    my question is, can anyone?
    when you see blue and green light,
    don't the wavelenghts add up to green anyways?
  9. Nov 16, 2005 #8
    No, it's biology of the eye. It's all about the cones and rods, but mostly cones for color.
  10. Nov 16, 2005 #9
    so wavelenght-wise two waves, a blue and a yellow, arent the same as one, a green?
    they look the same but they are not?
    im confused
  11. Nov 16, 2005 #10
    I'll refer you too any of the good references on color vision. You're getting into more biology.
  12. Nov 16, 2005 #11
    Maybe, in part, colors are defined by the blackbody spectrum of the sun.
  13. Nov 17, 2005 #12
    No, color is not defined by blackbody radiation.
  14. Nov 17, 2005 #13


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    The answer lies primarily in the phototransduction mechanism in the eye, but there's a rough connection with averaging wavelengths as well. I'm certainly not qualified to discourse on this with any authority, but from my scant understanding...

    ...the crude version of the mechanism involves photoexcitation in the retina. Each such event creates a mobile electron-ion pair of related energy, which affect the membrane potential of the photoreceptor. This potential is what gets coded as a color.
    Last edited: Nov 17, 2005
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