Why Do You Need a Special Flash for a Digital Camera?
Most popular digital camera lines have inadequate flash systems and lack a connector for use with an external flash. Ordinary slave units will not work with most digital cameras because these cameras use a very rapid series of pre-flashes (we're not talking about red-eye reduction). The pre-flashes are used to set the white balance of the camera's image sensor chip - not the exposure. A typical slave unit will fire on the pre-flash it senses while the digital camera captures the image on the last flash. Thus, the extra light from the slave does not show up in the digital camera photo. Digi-Slave flash units are specially designed to fire on the correct flash sensed by their built in optical sensor and circuitry, thus solving the digital camera flash problem.
The Digi-Slave RF-50 Ring Flash has built in digital slave circuitry, no electrical connection to the camera is required and the ring flash needs only to be screwed on to the lens threads of your camera. It's great for shadow free macro work such as dental and catalog photography.