A flash produces an instantaneous flash of light (typically around 1/1000 of a second) at a color temperature of about 5500K 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 either refer to the flash of light itself, or as a colloquialism for the electronic flash unit which discharges the flash of light.
In lower-end photgraphy, flash units are commonly built directly into the camera, while higher-end cameras allows separate flash units to be mounted via a standardized accessory mount bracket. In professional studio photography, flashes often take the form of large, standalone units, or studio strobes, that are powered by special battery packs and synchronized with the camera from either a flash synchronization cable, radio transmitter, or light-triggered, meaning that only one flash unit needs to be synchronized with the camera, which in turn triggers the other units.
Types of flashesEdit
Electronic xenon flash lampEdit
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 (typically 1/1000 second). The majority of consumer cameras have this type of flash built in.
"Microflashes" are high-voltage flash units designed to discharge a flash of light with an exceptionally quick, sub-microsecond duration. These are commonly used in scientific photography for examining extremely fast moving objects or reactions, famous for producing images such as bullets tearing through balloons.
Magnesium powder flashEdit
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 shutter. The bulb could only be used once, and was too hot to handle immediately after use. "Flash cubes" of 4 bulbs were introduced for the Kodak Instamatic camera that allowed taking 4 images in a row as the cube automatically rotated 90 degrees to a fresh bulb upon firing.
A flash is commonly used indoors as the main light source where there is not enough other light for a desired shutter speed. A fill flash is a low powered flash mixed with ambient light, and is often used to illuminate shadows on the side of a subject facing the camera. Another technique, bouncing a flash, involves pointing a flash upwards off of a surface, often a white celling, where it is reflected back onto the subject. Bouncing creates a more natural light effect and lessens shadows and glare but requires more flash power than a direct flash.
List of camera flashesEdit
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