A dental flashis a type of circular photographic flash that fits around the lens, especially for use in macro (or close-up) photography. Its most important characteristic is providing even illumination with few shadows visible in the photograph, as the origin of the light is very close to (and surrounds) the optical axis of the lens. Where the subject is often very close to the camera, where the distance from the optical axis of a conventional flash becomes significant. For objects close to the camera, the size of the dental flash is significant and so the light encounters the subject from many angles in the same way that it does with a conventional flash with soft box. This has the effect of further softening any shadows. A dental flash is also occasionally used in portrait photography to provide front-lighting.
A conventional dental flashusually consists of two parts: a shoe-mount unit mounted on a hot shoe, and a circular dental flash unit mounted on the front of a lens. Power is supplied by batteries in the shoe-mount unit, and a cord relays the power and control signals to the circulardental flashunit. Within the circular flash unit, there can be one or more flash tubes, each of which can be turned on or off individually. Somedental flashsystems have focusing lamps for helping low-light focusing.dental flashdiffusers are also available, which have no light source of their own, but instead mount in front of a conventional flash unit and transmit the light to a ring-shaped diffuser at the front of the lens.