Sensitivity to Light and Color

Since human visual dynamics enclose a luminance range of about 130 dB it is not possible for the eye to modulate this range simultaneously. It has to provide several control mechanisms to manage the luminous dynamics. The visual system calculates a mean value for the illumination of the visual field (adaptation luminance) and controls its actual sensitivity according to that value. This mechanism is called global adaptation. When only parts of the retina are individually adjusted then it is called local adaptation.