A few posts ago, I said that while the colorspaces looked random, they really weren’t, and that there was underlying order. The structure cannot be easily seen just by looking at the numbers themselves, but at how the numbers are obtained.
The story begins sometimes in the 1950s, were transmitting color TV images started to be the next logical step. Someone (not sure who was first, but it may have been Valensi, in the 1930s) proposed that TV color should be encoded in a perceptually friendly way . It was known for a while that the retina had four types of sensors, rods for brightness with no color information, and three other types corresponding to red, green, and blue, but also that in, and beyond the retina, information travels as brightness, yellow-blue and red-green differences [2,3].