Aperture priority, often abbreviated ''A'' or ''Av'' (for aperture value) on a camera

mode dial A mode dial or camera dial is a dial used on digital cameras to change the camera's mode. Most digital cameras, including dSLR and mirrorless cameras, support modes, selectable either by a rotary dial or from a menu. On point-and-shoot camera ...

, is a mode on some cameras that allows the user to set a specific

aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...

value (

f-number An f-number is a measure of the light-gathering ability of an optical system such as a camera lens. It is calculated by dividing the system's focal length by the diameter of the entrance pupil ("clear aperture").Smith, Warren ''Modern Optical ...

) while the camera selects a

shutter speed In photography, shutter speed or exposure time is the length of time that the film or digital sensor inside the camera is exposed to light (that is, when the camera's shutter (photography), shutter is open) when taking a photograph. The am ...

to match it that will result in proper exposure based on the lighting conditions as measured by the camera's

light meter A light meter (or illuminometer) is a device used to measure the amount of light. In photography, an exposure meter is a light meter coupled to either a Digital data, digital or analog calculator which displays the correct shutter speed and f-nu ...

. This is different from manual mode, where the user must decide both values,

shutter priority Shutter priority (usually denoted as S on the mode dial), also called time value (abbreviated as Tv), refers to a setting on cameras that allows the user to choose a specific shutter speed while the camera adjusts the aperture to ensure correct ...

where the user picks a shutter speed with the camera selecting an appropriate aperture, or

program mode Most digital cameras support the ability to choose among a number of configurations, or '' modes'' for use in various situations. Professional DSLR cameras provide several manual modes; consumer point-and-shoot cameras emphasize automatic modes ...

where the camera selects both.

Uses

Depth of field

As an image's

depth of field The depth of field (DOF) is the distance between the nearest and the farthest objects that are in acceptably sharp focus (optics), focus in an image captured with a camera. See also the closely related depth of focus. Factors affecting depth ...

is inversely proportional to the size of the lens's aperture, aperture priority mode is often used to allow the photographer to control the focus of objects in the frame. Aperture priority is therefore useful in

landscape photography Landscape photography (often shortened to landscape photos) captures the world's outdoor spaces, sometimes vast and unending and other times microscopic. Landscape photographs typically capture the presence of nature but can also focus on human-ma ...

, for example, where it may be desired that objects in foreground, middle distance, and background all be rendered crisply, while shutter speed is immaterial. To obtain this large depth of field, a narrow aperture (identified by a ''high'' f-number, e.g. f/16 or f/22) is necessary. Aperture priority mode also finds use in

portrait photography Portrait photography, or portraiture, is a type of photography aimed toward capturing the personality of a person or group of people by using effective Photographic lighting, lighting, Painted photography backdrops, backdrops, and poses. A portr ...

, where a wide aperture (identified by a ''low'' number, e.g. f/1.4 or f/2.8) and therefore smaller depth of field may be desired to throw the background out of focus and make it less distracting.

Shutter speed

Another common use of aperture priority mode is to indirectly affect shutter speed for a desired effect. In landscape photography, a user might select a small aperture when photographing a

waterfall A waterfall is any point in a river or stream where water flows over a vertical drop or a series of steep drops. Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf. Waterfalls can be formed in seve ...

, so that the camera will select a slow shutter speed (to allow a sufficient amount of light to reach the

film A film, also known as a movie or motion picture, is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, emotions, or atmosphere through the use of moving images that are generally, sinc ...

sensor A sensor is often defined as a device that receives and responds to a signal or stimulus. The stimulus is the quantity, property, or condition that is sensed and converted into electrical signal. In the broadest definition, a sensor is a devi ...

for proper exposure), thereby causing the water to blur through the frame. At the contrary, a larger aperture allows to shorten the shutter speed reducing the hand jitter by taking a picture without a tripod or, in alternative, a lower ISO to enhance the image quality by reducing the noise. When shooting a portrait in dim lighting, the photographer might choose to open the lens to its maximum aperture in hopes of getting enough light for a good exposure while maintaining the shortest possible shutter speed to reduce blur.

References

Camera features {{Photo-stub