Ring flash

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A ring flash, invented by Lester A. Dine, in 1952 originally for use in dental photography^{[citation needed]}, is a 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. When the subject is very close to the camera, as is the case in macro photography, the distance of the flash from the optical axis becomes significant. For objects close to the camera, the size of the ring 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.

Ring flashes are also very popular in portrait and fashion photography. In addition to softening shadows which can be unflattering to models and bring out unsightly wrinkles, the unique way that ring flashes render light give the model a "glowing" appearance which is often sought after by some magazines like Maxim^{[citation needed]}.

Macro ring flash usually consists of two parts: a shoe-mount unit mounted on a hot shoe, and a circular 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 circular flash unit. For larger ring flash units like those used for fashion photography, power is usually delivered by a power pack which can be battery or AC powered. Some ring flashes however, like ones made by Alien Bees, are constructed like mono lights where the light and power are contained in one unit. Within the circular flash unit, there can be one or more flash tubes, each of which can be turned on or off individually. Some ring flashes have focusing lamps for helping low-light focusing. Ring flash diffusers 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.