A shutter can also be used to allow pulses of light to pass outwards, as in a movie projector or signal lamp.
Camera shutters can be fitted in two positions:
- Central shutters are mounted within a lens assembly, or more rarely behind or even in front of a lens and shut off the beam of light where it is narrow. A leaf mechanism is usually used.
- Focal plane shutters are mounted near the focal plane and move to uncover the film or sensor.
Shutters immediately behind the lens were used in some cameras with limited lens interchangeability. Shutters in front of the lens were used in the early days of photography.