A burst of artificial light used to provide all or some of the illumination for an image. Most cameras have built-in flash units, while some allow a separate flash unit to be attached via the hotshoe, or used off-camera. In studio work, large
standalone flash units or strobes use mains power, and are triggered by a flash sync cable or radio signal. Flash durations are usually between 1/200 to 1/1000 sec and have a colour temperature of around 5,500-6,000k.