If an LED emits 3 wavelengths of light, rgb, and pigments reflect specific wavelengths, then the pigment should only reflect one of 6 possible wavelength combinations. How in reality do the pigments create a more complete spectrum of color to the human eye, out of the 3 wavelengths?

Maybe the reflected wavelength is actually absorbed a unique percentage of the time by the pigment, and that could vary the brightness of the reflected light, but I don't know about changing the color altogether. Also, many pigments' emission spectrums don't line up with the LED's wavelengths, thus shouldn't they appear black under the LED?

  • $\begingroup$ It is not just the number of wavelengths but the intensity of each wavelength which results in your sensation of colour. $\endgroup$
    – Farcher
    Apr 29, 2018 at 10:41
  • $\begingroup$ It seems strange that a pigment could modify the amplitude of a photon by reflecting it. $\endgroup$
    – John Doe
    Apr 29, 2018 at 10:49
  • 1
    $\begingroup$ The pigment does not change the amplitude of a phton! The pigment alters the number of photons of a particular wavelength entering your eye per second. $\endgroup$
    – Farcher
    Apr 29, 2018 at 10:55
  • $\begingroup$ Consider: a video monitor uses just 3 base colours to produce all of the colours that it displays. But 3 pigments don't produce a full spectrum, they produce a limited gamut. $\endgroup$
    – PM 2Ring
    Apr 30, 2018 at 12:30

1 Answer 1


as @farcher points out, pigmented surfaces illuminated by a 3-color LED array subtract some wavelengths in that 3-color mix more than others, changing the individual red/green/blue (RGB) proportions in the light beam that reaches your eye. So the light rays that enter your eye remain strictly an RGB mixture.

But your eye and brain interpret those three color proportions as a continuous spectrum of color possibilities (orange, purple, yellow, etc.) which in the case of an RGB source are not present in the beam entering your eye. this neurophysiological phenomenon is called metamerism and is the reason your eye can experience a full spectrum of colors even when it is being stimulated by only a mixture of red, green, and blue photons.


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