Center Surround Field refers to a two-tier system that detects an edge. This can be represented by a two input XOR gate where 1 = white, and 0 = black.
P Q
1 1 0
1 0 1
0 1 1
1 1 0
Since there are three colors, , [green XOR blue] implies <0, 1,1> as represented by the thin strip in the figure.
If an object sweeps past XOR inputs, a series of 1’s and 0’s are generated. An object that is closer generates a longer cycle since there is, apparently, a longer input series.
Ape Town 