Shutter priority refers to a setting on some cameras that allows the user to choose a specific shutter speed

Shutter speed

In photography, shutter speed is a common term used to discuss exposure time, the effective length of time a camera's shutter is open....

 while the camera adjusts the aperture

Aperture

In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...

 to ensure correct exposure

Exposure (photography)

In photography, exposure is the total amount of light allowed to fall on the photographic medium during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value and scene luminance over a specified area.In photographic jargon, an exposure...

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

Aperture priority

Aperture priority, often abbreviated A or Av on a camera mode dial, is a setting on some cameras that allows the user to choose a specific aperture value while the camera selects a shutter speed to match. The camera will ensure proper exposure...

 where the user picks an aperture with the camera selecting the shutter speed to match, or program mode where the camera selects both.

Shutter priority with longer exposures is chosen to create an impression of motion. For example, a waterfall will appear blurred and fuzzy. If the camera is panned with a moving subject, the background will appear blurred. When photographing sports or high-speed phenomena, shutter priority with short exposures can ensure that the motion is effectively frozen in the resulting image.

Shutter priority is often abbreviated as S (with Nikon, Minolta, Konica Minolta, Sony, Olympus, Sigma) or Tv (for "time value" with Canon, Pentax, Leica) on a camera mode dial

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 SLR-like cameras, support modes, selectable either by a dial or from a menu. On point-and-shoot cameras which support modes a range of scene types is offered. On dSLR...

.