Shutter
The shutter of a camera or of the lens/shutter unit for a camera isolates the film in the camera from light until the shutter will be released. Depending on the shutter type releasing the shutter means to open it for a moment like a diaphragm, like a roller blind, or simply like a sliding door. A wind-up-mechanism or a litte electric servo delivers the shutter movement energy and controls the time of film enlightening. Focal plane shutter means that the shutter is located near the film plane. Most focal plane shutters are of the roller blind type, as light-tight roller blind over the rectangled window over the film plane, with a second roller blind closing the shutter window immediately when the other is opened or just opening. Fast shutter speeds are achieved by letting the light in through a narrow gap between the opening and the closing roller blind.
