Abstract: In a double-beam photometer comprising a light source providing a light beam, detector means, a sample area, optical means for guiding the light beam as a measuring light beam through the sample area onto the detector means, means for guiding the same light beam as a reference light beam onto the detector means while avoiding the sample area, and chopper means disposed in a splitting location for splitting the light beam into the measuring light beam, which are combined into one path of rays in a recombination location, after the measuring light beam has passed through the sample area, with the splitting location and the recombination location being spatially close to each other. The chopper means has a single chopper which simultaneously effects the splitting and the combination of the measuring and reference light beams.