Reciprocity (photography)
In photography reciprocity is the inverse relationship between the intensity and duration of light that determines the reaction of light-sensitive material. Within a normal exposure range for film stock, for example, the reciprocity law states that the film response will be determined by the total exposure, defined as intensity × time. Therefore, the same response (for example, the optical density of the developed film) can result from reducing duration and increasing light intensity, and vice versa.
The reciprocal relationship is assumed in most sensitometry, for example when measuring a Hurter and Driffield curve (optical density versus logarithm of total exposure) for a photographic emulsion. Total exposure of the film or sensor, the product of focal-plane illuminance times exposure time, is measured in lux seconds.
Read more about Reciprocity (photography): History, In Chemical Photography, Reciprocity Failure, Schwarzschild Law, The Kron–Halm Catenary Equation, Quantum Reciprocity-failure Model, Astrophotography, Holography
Famous quotes containing the word reciprocity:
“Between women love is contemplative; caresses are intended less to gain possession of the other than gradually to re-create the self through her; separateness is abolished, there is no struggle, no victory, no defeat; in exact reciprocity each is at once subject and object, sovereign and slave; duality become mutuality.”
—Simone De Beauvoir (1908–1986)