flash photography

Flash photography

A flash is a device used in photography producing a flash of artificial light typically 1/1000 to 1/200 of a second at a color temperature of about 5500 K to help illuminate a scene. One of the main purposes of flash is to illuminate a dark scene. Other uses are capturing quickly moving objects or changing the quality of light. Most current flash units are electronic, having evolved from single-use flashbulbs and flammable powders. More modern cameras often activate flash automatically. Flash units are commonly built directly into a camera. Some cameras allow separate flash units to be mounted. In professional studio equipment, flashes may be large, or studio strobes, powered by special battery packs or connected to mains power. They are either synchronized with the camera using a cable or radio signal, or are light-triggered, meaning that only one flash unit needs to be synchronized with the camera, and in turn triggers the other units. The earliest flashes had of a quantity of flash powder consisting of a mechanical mixture of magnesium powder and potassium chlorate that was ignited by hand. Later, magnesium filaments were contained in flash bulbs filled with oxygen gas, 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.