focal plane shutter

Definition: Mechanism for exposing photodetector or film to light for a precise period of time. * Consists of two sets of opaque roller blinds or blades which traverse the film-gate at constant speed with a slit of adjustable width: a narrow slit provides a short exposure, a wide slit provides a long exposure. * The slit may run vertically or horizontally, progressively exposing the film or detector.

Related Terms: shutter time, shutter speed

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