A flash is a device used in photography that produces an instantaneous flash of artificial light (typically around 1/1000 to 1/200 of a second) at a color temperature of about 5500 K to help illuminate a scene. While flashes can be used for a variety of reasons (e.g., capturing quickly moving objects, creating a different temperature light than the ambient light) they are mostly used to illuminate scenes that do not have enough available light to adequately expose the photograph. The term flash can refer either to the flash of light itself or, colloquially, to the electronic flash unit which discharges the flash of light. The vast majority of flash units today are electronic, having evolved from single-use flash-bulbs and flammable powders.
Flash units are commonly built directly into the camera. In addition, many cameras allow separate flash units to be mounted via a standardized accessory mount bracket often called a "hot shoe". In professional studio photography, flashes often take the form of large, standalone units, or studio strobes, that are powered by either special battery packs or connected directly to the mains and synchronized with the camera from either a flash synchronization cable, radio transmitter, or are light-triggered, meaning that only one flash unit needs to be synchronized with the camera, which in turn triggers the other units.