Editing Shutter speed (section)

==Introduction==
[[File:Shutter Speed Fan.gif|left|thumb|upright|Different shutter speeds for a CPU fan. Shutter speeds from first to last: 2&nbsp;s, 1&nbsp;s, {{frac|10}}&nbsp;s, {{frac|100}}&nbsp;s, {{frac|200}}&nbsp;s, {{frac|500}}&nbsp;s, {{frac|1000}}&nbsp;s, {{frac|2000}}&nbsp;s, {{frac|4000}}&nbsp;s]]{{Inline citations|date=May 2023|section}}
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 (photography)|exposure]]). [[Exposure value]] (EV) is a quantity that accounts for the shutter speed and the f-number. Once the sensitivity to light of the recording surface (either film or sensor) is set in numbers expressed in "[[Film speed#ISO|ISOs]]" (e.g. 200 ISO, 400 ISO), the light emitted by the scene photographed can be controlled through aperture and shutter-speed to match the film or sensor sensitivity to light. This will achieve a good exposure when all the details of the scene are legible on the photograph. Too much light let into the camera results in an overly pale image (or "over-exposure") while too little light will result in an overly dark image (or "under-exposure").{{Citation needed|date=May 2023}}

Multiple combinations of shutter speed and f-number can give the same exposure value (E.V.). According to [[exposure value]] formula, doubling the exposure time doubles the amount of light (subtracts 1 EV).  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. For example, {{f/|8}} lets four times more light into the camera as {{f/|16}} does. A shutter speed of {{frac|50}}&nbsp;s with an {{f/|4}} aperture gives the same exposure value as a {{frac|100}}&nbsp;s shutter speed with an {{f/|2.8}} aperture, and also the same exposure value as a {{frac|200}}&nbsp;s shutter speed with an {{f/|2}} aperture, or {{frac|25}}&nbsp;s at {{f/|5.6}}.{{Citation needed|date=May 2023}}

In addition to its effect on exposure, the shutter speed changes the way movement appears in photographs. Very short shutter speeds can be used to freeze fast-moving subjects, for example at sporting events. Very long shutter speeds are used to intentionally blur a moving subject for effect.<ref>{{cite book | title = The Complete Guide to Night and Low-Light Photography | author = Lee Frost | publisher = Amphoto Books | year = 2000 | isbn = 0-8174-5041-6 | url = https://books.google.com/books?id=IugNeG0vIMcC&pg=RA1-PA142  }}</ref> Short exposure times are sometimes called "fast", and long exposure times "slow".{{Citation needed|date=May 2023}}

Adjustments to the aperture need to be compensated by changes of the shutter speed to keep the same (right) exposure.

In early days of photography, available shutter speeds were not standardized, though a typical sequence might have been {{frac|10}}&nbsp;s, {{frac|25}}&nbsp;s, {{frac|50}}&nbsp;s, {{frac|100}}&nbsp;s, {{frac|200}}&nbsp;s and {{frac|500}}&nbsp;s; neither were apertures or film sensitivity (at least 3 different national standards existed). 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.), a standardized 2:1 scale was adopted for shutter speed so that opening one aperture stop and reducing the amount of time of the shutter speed by one step resulted in the identical exposure. The agreed standards for shutter speeds are: {{enum |comma=;{{sp}} |and=; and{{sp}} |{{frac|1000}}&nbsp;s |{{frac|500}}&nbsp;s |{{frac|250}}&nbsp;s |{{frac|125}}&nbsp;s |{{frac|60}}&nbsp;s |{{frac|30}}&nbsp;s |{{frac|15}}&nbsp;s |{{frac|8}}&nbsp;s |{{frac|4}}&nbsp;s |{{frac|2}}&nbsp;s |1&nbsp;s }}.<ref name=kahn>{{cite book | title = Essential Skills for Nature Photography | author = Cub Kahn | url = https://books.google.com/books?id=EZhNY--TZjIC&pg=PT21 |isbn = 1-58428-009-3 | year = 1999 | publisher = Amherst Media}}</ref>

[[File:Phatman - Lightning on the Columbia River (by-sa).jpg|thumb|right|upright|An extended exposure can also allow photographers to catch brief flashes of light, as seen here. Exposure time 15 seconds.]]
With this scale, each increment roughly doubles the amount of light (longer time) or halves it (shorter time).

Camera shutters often include one or two other settings for making very long exposures:
* '''B''' (for ''[[bulb (photography)|bulb]]'') keeps the shutter open as long as the shutter release is held.
* '''T''' (for ''time'') keeps the shutter open (once the shutter-release button had been depressed) until the shutter release is pressed again.{{Citation needed|date=May 2023}}

The ability of the photographer to take images without noticeable blurring by camera movement is an important parameter in the choice of the slowest possible shutter speed for a handheld camera. The rough guide used by most [[135 film|35 mm]] photographers is that the slowest shutter speed that can be used easily without much blur due to camera shake is the shutter speed numerically closest to the lens focal length. For example, for handheld use of a 35&nbsp;mm camera with a 50&nbsp;mm [[normal lens]], the closest shutter speed is {{frac|60}}&nbsp;s (closest to "50"), while for a 200&nbsp;mm lens it is recommended not to choose shutter speeds below {{frac|200}}&nbsp;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. Through practice and special techniques such as bracing the camera, arms, or body to minimize camera movement, using a monopod or a tripod, slower shutter speeds can be used without blur. If a shutter speed is too slow for hand holding, a camera support, usually a [[Tripod (photography)|tripod]], must be used. [[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|date=May 2023}}

Shutter priority refers to a shooting mode used in cameras. It allows the photographer to choose a shutter speed setting and allow the camera to decide the correct aperture. This is sometimes referred to as [[shutter priority|Shutter Speed Priority Auto Exposure]], or TV (time value on Canon cameras) mode, S mode on Nikons and most other brands.{{Citation needed|date=May 2023}}