Other devices are available that project light in a fashion similar to ring flashes. 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. These adapters use diffusers and reflectors to "bend" the light in an arc around the lens axis and then emit the light from that arc. These devices maintain any through-the-lens (TTL) lighting functions that are shared by the camera and flash because the timing of the light has not changed.