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Comment by golergka | Hacker News Reader

> color space is 2D

Human eyes have three different color receptors, each tuned for it's own frequency, so it's already 3d. However, apart from human perception, color, just like sound, can have any combinations of frequencies (when you split the signal with Fourier transform), and may animals do have more receptors than us.

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Humans perceive all stimulation in the same raito of the L, M, and S cones to be the same color, but with different brightnesses. So only two dimensions are nessesary to represent human visible colors, hence HSV or L*a*b* space.

According the opponent process model of colour perception you need three axes to represent all colours: luminosity [L+M+S+rods], red-green [L-M] and blue-yellow [S - (L+M)].

There is a fair point there, but a few things - HSV and Lab are only models, they don’t necessarily capture all visible colors (esp. when it comes to tetrachromats). Brightness is a dimension, and can affect the perception of a color, esp. as you get very bright - HSV and Lab are 3D spaces. Arguing that brightness should be ignored or factored out is problematic and only a small step from arguing that saturation should be factored out too and that color is mostly one dimensional.

You only need to mix two different wavelengths to render any human perceptible color. They give you four parameters to work with (wavelength1, brightness1, wavelength2, brightness2) which makes it an underdetermined system with an infinite number of solutions for all but the pure, spectral boundary of the gamut.

In this sense our hearing is much better than our color vision.

We can distinguish the combination a huge number of frequencies between 20-20000Hz.

But we can only distinguish 3 independent colors of light.

Of course our vision is vastly better than hearing for determining where the sound/light comes from.

Total tangent, but is that because of the wavelengths involved? I imagine a “sound camera” would have to be huge to avoid diffraction (but that’s just intuition), requiring impracticality large ears. Likewise i imagine that perceiving “chords” of light requires sensing on really tiny scales, requiring impractically small complex structure in the eyes?

Anybody know the answer?

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