The sensitivity of microphotometers has been im-proved by signal processing, compensating fluctuations in the light source, and by modifying the beam pass. A signal/noise ratio of 4,000 was achieved which allows the detection of invisible variations of light intensities. The spatial resolution of mechanical scanning stages is close to the resolution of the microscope. When equipped with optimal diaphragms the scanning microphotometer can be regarded as a linear imaging system and characterized by a transfer function. It pro-vides digital images of microscopical specimens without loss of spatial resolution but improved contrast.