Abstract: A method and apparatus for the photometric measurement of the transmission or reflection of radiation on a test specimen or measuring object, especially for the final automatic inspection or quality control, for instance, of vacuum-deposited discs with respect to uniformly of the coating or the like, comprises a photometer with a chopper disc in the ray path and with at least one detector (sensor) and a detector amplifier (measuring signal amplifier). In order to achieve that the measurement can be employed under production conditions in on-line operation on moving measuring objects reliably for a long time, the invention provides that the measuring signals are numerically determined directly at the output of each detector amplifier by a fast analog-to-digital conversion and are subsequently processed further in two stages exclusively digitally by peak value determination, combined with averaging, within at least two chopper periods to form a transmission or reflection measurement value.