Color vision

One can attempt to draw an analogy between color vision and signal (or information) processing. In this case one considers a color stimulus as a “signal” made of three inputs (the three cones) and yielding three outputs, corresponding to three channels  [] :

1. The blue-yellow channel: the nerves response results from the antagonistic excitation coming from the addition of R and V cones versus the B cone excitation (output is B-(R+V))

2. The green-red channel yielding a response which opposes the R cones to the V cones (output is V-R);

3. The achromatic (or contrast) channel yielding an additive response coming from the excitation of V and R cones: this signal carries the information about the light level (luminance), notwithstanding the spectral content of the incoming light.

The analogy presented here does not describe the whole physiological process of color vision but is just a simplified result of these processes. In particular the notion of channel is certainly too simple and has to be refined. Color information processing is today described by the opponent color code theory based on many experimental results [] []