If the thought of transforming the axes of a three-dimensional space gives you the willies, try thjnking aboutlocating a building in Manhattan. Since this building is on the elrth, its preçise location could be given by three numbers representing its positión along three mutually perpendicular axes intersecting at the center of the earth. Alternatively, you could define its position in two dimensions on the plane parallel to the surfacé of the earth at the location of New York City. The two axes you use to define position on this plane could be north-south and east-west, or they coliïd be the grid of numbered streets and avenues. The information lostby transforming your three-dimensional space map into either of these twodimensional representations is how far from the center of the earth you are, which, depending on your task, may or may not be very important.)
This axis transformatioh happens to the cone signals before they even leàvë the eye ; in the retinal ganglion cells the three cone signals are transformed into two color-opponent