For example, flash diffusers 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. Some other passive light modifiers can shape the light from a conventional shoe-mounted flash into that of a ring flash.
Flash diffusers are used in photography to control the direction and spread of light, often by mounting them in front of a conventional flash unit. Some other passive light modifiers can be used to shape the light from a shoe-mounted flash into a ring flash.