Shutter speed

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Shutter speed can have a dramatic impact on the appearance of moving objects. Changes in background blurring are apparent from the need to adjust the aperture size to achieve proper exposure.

The shutter speed dial of a Nikkormat EL

Slow shutter speed combined with panning the camera can achieve a motion blur for moving objects.

A photo of street at night (exposure time 30 seconds)

A pinwheel photographed at three different shutter speeds

[edit] Introduction

Factors that affect the total exposure of a photograph include the scene luminance, the aperture size (f-number), and the exposure time (shutter speed); photographers can trade off shutter speed and aperture by using units of stops. A stop up and down on each will halve or double the amount of light regulated by each; exposures of equal exposure value can be easily calculated and selected. For any given total exposure, or exposure value, a fast shutter speed requires a larger aperture (smaller f-number). Similarly, a slow shutter speed, a longer length of time, can be compensated by a smaller aperture (larger f-number).

Slow shutter speeds are often used in low light conditions, extending the time until the shutter closes, and increasing the amount of light gathered. This basic principle of photography, the exposure, is used in film and digital cameras, the image sensor effectively acting like film when exposed by the shutter.

Shutter speed, or more literally exposure time, is measured in seconds, but often marked in reciprocal seconds. A typical exposure time for photographs taken in sunlight is 1/125th of a second, typically marked as 125 on a shutter speed setting dial. In addition to its effect on exposure, shutter speed changes the way movement appears in the picture. Very short shutter speeds are used to freeze fast-moving subjects, for example at sporting events. Very long shutter speeds are used to intentionally blur a moving subject for artistic effect.^[1]

Adjustment to the aperture controls the depth of field, the distance range over which objects are acceptably sharp; such adjustments generally need to be compensated by changes in the shutter speed.

In early days of photography, available shutter speeds were somewhat ad hoc.^[2] Following the adoption of a standardized way of representing 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 shutter speed by one step resulted in the identical exposure. The agreed standards for shutter speeds are:^[3]

• 1/1000 s
• 1/500 s
• 1/250 s
• 1/125 s
• 1/60 s
• 1/30 s
• 1/15 s
• 1/8 s
• 1/4 s
• 1/2 s
• 1 s

An extended exposure can also allow photographers to catch brief flashes of light, as seen here. Exposure time 15 seconds.

Each standard increment either doubles the amount of light (longer time) or halves the amount of light (shorter time). For example, if you move from 1 sec to 1/2 second, you have effectively halved the amount of light entering the shutter. This scale can be extended at either end in specialist cameras. Some older cameras use the 2:1 ratio at slightly different values, such as 1/100 s and 1/50 s, although mechanical shutter mechanisms were rarely precise enough for the difference to have any significance.

The term "speed" is used in reference to short exposure times as fast, and long exposure times as slow. Shutter speeds are often designated by the reciprocal time, for example 60 for 1/60 s.

Camera shutters often include one or two other settings for making very long exposures:

• B (for bulb) — keep the shutter open as long as the shutter release is held
• T (for time) — keep the shutter open until the shutter release is pressed again

The ability of the photographer to take images without noticeable blurring by camera movement is an important parameter in the choice of slowest possible shutter speed for a handheld camera. The rough guide used by most 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 mm camera with a 50 mm normal lens, the closest shutter speed is 1/60 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 longer shutter speeds can be used without blur. If a shutter speed is too slow for hand holding, a camera support — usually a tripod — must be used. Image stabilization can often permit the use of shutter speeds 3–4 stops slower (exposures 8–16 times longer).

Shutter priority refers to a shooting mode used in semi-automatic 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 Speed Priority Auto Exposure, or Tv (time value) mode.

[edit] Creative utility in photography

Sparklers moved in a circular motion with a exposure time of 4 seconds

In photography, shutter speed is a common term used to discuss exposure time, the effective length of time a shutter is open;^[2] the total exposure is proportional to this exposure time, or duration of light reaching the film or image sensor.

Shutter speed is one of several methods used to control the amount of light recorded by the camera's digital sensor or film. It is also used to manipulate the visual effects of the final image beyond its luminosity.

Images taken with a lower shutter speed invoke a visual sense of movement. Exposure time 3 seconds.

Slower shutter speeds are often selected to suggest movement in a still photograph of a moving subject.

Excessively fast shutter speeds can cause a moving subject to appear unnaturally frozen. For instance, a running person may be caught with both feet in the air with all indication of movement lost in the frozen moment.

When a slower shutter speed is selected, a longer time passes from the moment the shutter opens till the moment it closes. More time is available for movement in the subject to be recorded by the camera.

A slightly slower shutter speed will allow the photographer to introduce an element of blur, either in the subject, where, in our example, the feet, which are the fastest moving element in the frame, might be blurred while the rest remains sharp; or if the camera is panned to follow a moving subject, the background is blurred while the subject remains sharp.

The exact point at which the background or subject will start to blur depends on the rate at which the object is moving, 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.

When slower shutter speeds, in excess of about half a second, are used on running water, the photo will have a ghostly white appearance reminiscent of fog. This effect can be used in landscape photography.

Zoom burst is a technique which entails the variation of the focal length of a zoom lens during a longer exposure. In the moment that the shutter is opened, the lens is zoomed in, changing the focal length during the exposure. The center of the image remains sharp, while the details away from the center form a radial blur, which causes a strong visual effect, forcing the eye into the center of the image.^[4]

The following list provides an overview of common photographic uses for standard shutter speeds.

• 1/8000 s: The fastest speed available in production SLR cameras as of 2009. Used to take sharp photographs of very fast subjects, such as birds or planes, under good lighting conditions, with a ISO number of 1,000 or more and a large aperture lens.^[5]
• 1/4000 s: The fastest speed available in consumer SLR cameras as of 2009. Used to take sharp photographs of fast subjects, such as athletes or vehicles, under good lighting conditions and with an ISO setting of up to 800.^[6]
• 1/2000 s and 1/1000 s: Used to take sharp photographs of moderately fast subjects under normal lighting conditions. 1/1000 s is the slowest speed that will reliably prevent image shake in unstabilized handheld shots.^[7]
• 1/500 s and 1/250 s: Used to take sharp photographs of people in motion in everyday situations. 1/250 s is the fastest speed useful for panning; it also allows for a larger aperture (up to f/11) in motion shots, and hence for a narrower depth of field.^[8]

The Whirligig ride during night at SFGAm at an exposure time of 0.8 Seconds.

• 1/125 s: This speed, and longer ones, are no longer useful for freezing motion. 1/125 s is used to obtain greater depth of field and overall sharpness in landscape photography, and is also often used for panning shots.
• 1/60 s: Used for panning shots, for images taken under dim lighting conditions, and for available light portraits.^[9]
• 1/30 s: Used for panning subjects moving slower than 30 miles per hour (48 km/h) and for available light photography. Images taken at this and slower speeds normally require a tripod or other camera support to be sharp.^[10]
• 1/15 s and 1/8 s: This and slower speeds are useful for photographs other than panning shots where motion blur is employed for deliberate effect, or for taking sharp photographs of immobile subjects under bad lighting conditions with a tripod-supported camera.^[11]

• 1/4 s, 1/2 s and 1 s: Also mainly used for motion blur effects and/or low-light photography, but only practical with a tripod-supported camera.^[12]
• 1 minute to several hours: Used with a mechanically fixed camera in astrophotography and for certain special effects.^[13]

[edit] Cinematographic shutter formula

Motion picture cameras used in traditional film cinematography employ a mechanical rotating shutter. The shutter rotation is synchronized with film being pulled through the gate, hence shutter speed is a function of the frame rate and shutter angle. With traditional shutter angle of 165° or 180° the film is exposed for 1/48 or 1/50 second at a standard 24 frame/s.^[14]

Where E = shutter speed (reciprocal of exposure time in seconds), F = Frames per second, and S = Shutter angle:^[14]

, for E in reciprocal seconds

Digital video cameras do not have mechanical shutter and allow setting shutter speed directly in time units. Professional video cameras often allow selecting shutter speed in terms of shutter angle instead of time units, especially those that are capable of overcranking or undercranking.

[edit] References

• Doeffinger, Derek (2009). Creative Shutter Speed: Master Your Camera’s Most Powerful Control. Wiley. ISBN 978-0-470-45362-9. 

[edit] Footnotes

[edit] See also

Wikimedia Commons has media related to: Shutter speed

• exposure
• shutter
• f-number
• exposure value