Andrei Alexandrovich Gershun (1903-6.12.1952) was a Soviet physicist and a professor (1933). He was a son of A. L. Gershun. He graduated from Leningrad University. From 1920 he worked at the State Optical Institute (from 1934 as head of a laboratory), and from 1946 he was also head of a department at the Leningrad Institute of Precision Mechanics and Optics.
His research concerned physical optics, theoretical photometry and lighting engineering. He developed the general theory of the light field (1936), in which he extended the ideas of a physical field to light calculations for any distribution of centres that emit, absorb and scatter light. He introduced the concepts of the volume density of energy and of the light vector. He solved a number of practical problems in the design of natural lighting and derived the dependence of the illumination coefficient on the geometrical parameters of the source. He introduced the concept of equivalent luminance (1942). He studied the propagation of daylight and artificial light in the depths of the sea and extended the general photometric theory of the passage of light through turbid media. He is the founder of Soviet hydro-optics. He developed a method of visual spectrophotometry in the infrared region.