Real World Digital Photography, 2nd edition

The Shutter

The shutter is a complicated mechanism that precisely controls how long the light passing through the lens is able to continue on to the film or digital sensor at the back of the camera.

With a film camera, the shutter remains closed to prevent light from exposing the film until a picture is taken. With a digital camera—depending on the type of sensor used—a shutter in the traditional sense may not even be necessary. Because the imaging sensor in a digital camera is an electronic device rather than a light-sensitive chemical, it can be turned on and off electronically, eliminating the need for a mechanical shutter to control the flow of light. Some sensors still require the use of a shutter, but many digital cameras don't use a mechanical ...