flash (photography)

In photography, a flash is a device that produces an instantaneous flash of light (between 1/1000 of a second to 1/50,000 of a second) to help illuminate a scene. While flashes can be used for a variety of reasons (e.g. capturing very quickly moving subjects) they are mostly used to illuminate scenes that do not have enough available light to adequately expose the photograph. The term flash can either refer to the flash of light itself, or as a colloquialism for the electronic flash unit which is discharging the flash of light. The vast majority of flash units today are electronic, having evolved from single-use flash-bulbs and inflammable powders.

Types of flashes

The earliest flashes consisted of a wad of magnesium powder that was ignited by hand. Later, magnesium filaments were contained in flash bulbs, and electrically ignited by a contact in the camera shutter; such a bulb could only be used once, and was too hot to handle immediately after use, but the confinement of what would otherwise have amounted to a small explosion was an important advance. For the Kodak Instamatic camera, flash cubes of 4 bulbs were introduced, that allowed taking 4 images in a row as the cube automatically rotated 90 degrees to a fresh bulb upon firing. The later Magicube was noteworthy in that each bulb was set off by a plastic pin striking a pyrotechnic element in the flash, so that a battery was not required. Today's flash units are often electronic Xenon flash lamps. An electronic flash contains a tube filled with xenon gas, where electricity of high voltage is discharged to generate an electrical arc that emits a short flash of light. (A typical duration of the light impulse is 1/1000 second.) As of 2003, the majority of cameras targeted for consumer use have an electronic flash unit built in. A separate flash unit may usually be mounted to a camera via a standardised accessory mount bracket. When using a flash, the eyes of people in photos can appear red, this is caused by the red-eye effect.

Flash (Photography)

Types of flashes

See also