De Vries–Rose law

The De Vries–Rose law or Rose–de Vries law is a principle of vision science named after Hessel de Vries and Albert Rose. De Vries discovered it in 1943 from considerations of quantum efficiency, and Rose developed the idea substantially a few years later. The law says that for visual targets seen against a background luminance ${\displaystyle B}$, subject to certain assumptions, the threshold contrast should be inversely proportional to ${\displaystyle {\sqrt {B}}}$ (i.e. contrast sensitivity is directly proportional to ${\displaystyle {\sqrt {B}}}$). In reality it holds only approximately, at luminance levels between the regimes of "dark light" and Weber's Law.