The nonlinear relationship between brightness, hue and saturation in human vision becomes clear if, in addition to the pupil as brightness regulator, the inverted retina is interpreted as a cellular multilayer phase grating optical 3D chip, i.e. as a chromaticity and brightness regulator. Both regulators are optical information preprocessors which determine the signal input into the photoreceptors and thus represent the basis for subsequent electrical information processing in retinal neural networks. Data from the interference-optical 3D phase calculation (von Laue equation) are compared with experimental data on phenomena in human vision which are critical to this question, to show the interdependence of brightness, hue and saturation. This gives new insights into the function of the pupil, the Purkinje shift, the Bezold-Brucke phenomenon, the Stiles-Crawford aperture effects I/II and the saturation effects in human vision, all of which can be derived from a single pupil/retina/photopigment equation.