A leaf shutter is a type of shutter used in some cameras and lenses. Leaf shutters operate using a number of identically shaped blades (called leaves, hence the name) that have the ability to entirely close the light path (they are in many ways similar than as diaphragms used in apertures, except that leaf shutters are designed to close all the way).
Leaf shutters have a number of specific advantages over focal plane shutters:
• They are small and silent
• They allow flash synchronization at all shutter speeds
• fast moving objects do not produce a rolling shutter -effect
Leaf shutters also carry some disadvantages:
• Leaf shutters cannot reach as fast shutter speeds as focal plane shutters can
• If leaf shutters are in the camera (not in the lens), then leaf shutters typically place restrictions on maximum aperture and constrain lens designs.
• If leaf shutters are in the lens, then each lens needs its own leaf shutter (and is a pain to service)