The shutter is a device, mechanism or electronic function in a camera, be it still or video, which limits the amount of time in which light is exposed on the focus area or plane, whether that be an electronic light detector or a frame of film. Typically it consists of a thin mechanically driven plate that moves in and out of the path of light. Often it sits just in front of the focal plane or focusing area.
Being able to control the shutter speed determines a number of effects in the resulting image:
- The most important being that of the ability to stop or freeze action. Typically, the faster the shutter speed, the less obvious the effect of motion blur, especially of subjects moving at high speed. High shutter speeds also generally limit the amount of light falling on the focus area, useful for controlling exposure in brightly lit environments.
- Slow shutter speeds are useful in situations where there is a need to boost or increase the amount of light falling on the focusing area, as in low-light conditions. A drawback to this though is an increase in motion blur, especially if the camera is not mounted on a stabilising device like a tripod. Slow shutter speeds also can be used for artistic effect, as when there is a need to suggest the motion of a subject.