Some cameras allow an external flash, or hot shoe, to be mounted while in a professional studio, a photographer will use freestanding flash units, or strobes, which are either powered by the mains or connected to battery packs. The photographer synchronized them with the camera with the help of a cable or radio signal. Some are triggered by light, i.e. one flash can be synchronized with the camera, which triggers the other flash units.
Current camera flashes are either flashtubes, which combine a tube filled with xenon gas with a high voltage charge to emit a flash of light, or microflashes. Microflashes are high-voltage flash units which give a flash of light with for a sub-microsecond. They are frequently used by engineers or sometimes for examining fast moving objects or reactions.
Although they don't yet have the power to replace xenon flashes, LED flashes have been used in camera phones. The major advantage of LED over xenon is its ability to operate at a low voltage, on a tiny scale and with increased efficiency.
Current camera flashes are either flashtubes, which combine a tube filled with xenon gas with a high voltage charge to emit a flash of light, or microflashes. Microflashes are high-voltage flash units which give a flash of light with for a sub-microsecond. They are frequently used by engineers or sometimes for examining fast moving objects or reactions.
Although they don't yet have the power to replace xenon flashes, LED flashes have been used in camera phones. The major advantage of LED over xenon is its ability to operate at a low voltage, on a tiny scale and with increased efficiency.
Traditional flash lighting gives a harsh, one directional light, which is why professionals use softboxes and umbrellas. A flash is also used as filler light to illuminate part of a scene or subject that would otherwise be in shadows. Bounce flash is where the flash is pointed at a reflective surface like a wall, ceiling or umbrella and reflects light onto the scene. When used indoors is can light a whole scene more softly and naturally than a direct flash, although it will need more power when bounced. Bounced light can be also directed onto a subject by the use of bounce cards which can be attached to a flash unit.
A common problem with built in camera flashes is red eye. This happens because the retina reflects red light back towards the light source, which is why pictures taken in front of a subject often exhibit this. Red eye reduction (a pre-flash to make irises contract) now found on some cameras helps, but the best way to deal with it is to separate the flash unit from the camera, or by using bounce flash.
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