The camera's shutter speed, the lens's aperture or f-stop, and the scene's luminance together determine the amount of light that reaches the film or sensor (the exposure).
Reducing the aperture size at multiples of one over the square root of two lets half as much light into the camera, usually at a predefined scale of f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, and so on.
[citation needed] In addition to its effect on exposure, the shutter speed changes the way movement appears in photographs.
Soon this problem resulted in a solution consisting in the adoption of a standardized way of choosing aperture so that each major step exactly doubled or halved the amount of light entering the camera (f/2.8, f/4, f/5.6, f/8, f/11, f/16, etc.
For example, for handheld use of a 35 mm camera with a 50 mm normal lens, the closest shutter speed is 1⁄60 s (closest to "50"), while for a 200 mm lens it is recommended not to choose shutter speeds below 1⁄200 s. This rule can be augmented with knowledge of the intended application for the photograph, an image intended for significant enlargement and closeup viewing would require faster shutter speeds to avoid obvious blur.
Image stabilization on digital cameras or lenses can often permit the use of shutter speeds 3–4 stops slower (exposures 8–16 times longer).
[citation needed] Shutter speed is one of several methods used to control the amount of light recorded by the camera's digital sensor or film.
For instance, a running person may be caught with both feet in the air with all indication of movement lost in the frozen moment.
The exact point at which the background or subject will start to blur depends on the speed at which the object is moving, the angle that the object is moving in relation to the camera, the distance it is from the camera and the focal length of the lens in relation to the size of the digital sensor or film.
Motion picture cameras used in traditional film cinematography employ a mechanical rotating shutter.