Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

RGB to wavelenght or viceversa.

  1. Jul 9, 2005 #1
    How would one convert RGB values to a wavelength value
    OR
    a wavelength value to RGB?

    ie 180,180,60=?
     
    Last edited: Jul 9, 2005
  2. jcsd
  3. Jul 9, 2005 #2

    LeonhardEuler

    User Avatar
    Gold Member

    I think that may be impossible. A blend of different colors of light does not have a unique wavelength. For example, you can't talk about the wavelength of the color brown because it is a mixture of light at different wavelengths.
     
  4. Jul 9, 2005 #3
    but doesn't teh superposition mean that those different wavelengths...superimpose into one wave? with a wavelength because its a finite #?
     
  5. Jul 9, 2005 #4

    LeonhardEuler

    User Avatar
    Gold Member

    No, waves of different frequencies do not combine into a single, normal wave. For example you can add two cosine waves of different frequencies. Suppose the average frequency of the two waves is m and that one wave has frequency (m+x) and the other (m-x). Then the function describing the amplitude of the wave is A=cos[(m+x)t] + cos[(m-x)t]. Using Euler's formula, that becomes
    A = Re: e^[i(m+x)t] + e^[i(m-x)t]
    = Re: {e^(imt)}*{e^(ixt) + e^(-ixt)}
    = Re: {cos(mt) +i sin(mt)}*{cos(xt) + i sin(xt) + cos(-xt) + i sin(-xt)}
    = Re: {cos(mt) +i sin(mt)}*{2cos(xt)}
    = 2cos(mt)cos(xt)
    Which is not a simple cosine wave (It looks like a cosine wave on top of a cosine wave for x<<m)
    The eye contains three different light sensitive pigments which have maximum sensitivities at wavelengths corresponding roughly to red, green and blue. It is the relative extent to which these pigments are activated that determines what color is percieved. Each of these pigments can pick out of a complicated waveform that component of the the wave at the frequency to which it is most sensitive. No pure light could activate pigments that peak at different frequencies equally. This means that some colors can not be produced by pure light.
     
  6. Jul 10, 2005 #5
    "It is the relative extent to which these pigments are activated that determines what color is percieved."
    if so does this mean that the bipolar cells of the eye don't receive on/off signals from the cones&rods but REAL valued signals?
     
  7. Jul 10, 2005 #6

    LeonhardEuler

    User Avatar
    Gold Member

    The frequency with which a neuron is activated determines the percieved strength of the signal. For example, to use random numbers, if a cell with one pigment is activated 10 times a second and a different one is activated fifteen times a second, the brain will interpret this as meaning the second color is more abundant.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: RGB to wavelenght or viceversa.
  1. The RGB Color Model (Replies: 8)

Loading...