A mechanical shutter is a physical device inside a camera that regulates the duration for which light strikes the image sensor or film. It typically consists of one or two sets of blades, referred to as “shutter blades” or “curtains,” which open and close for a predetermined period. This period is called the exposure time, and by adjusting it, the photographer influences whether a fast-moving object in the picture will be sharp or, conversely, motion-blurred. In digital cameras, we most commonly encounter the focal-plane shutter (or slit shutter), positioned directly in front of the sensor, which exposes the image progressively by the movement of a narrow slit between the blades. Less common is the leaf shutter (or central shutter), which is built into the lens.
