Designed to work with a camera's TTL meter, the 34iAF is a dedicated auto focus flash unit that will operate simply and reliably on auto focus SLR cameras. NISSIN designed the CPU of the flash to communicate with the CPU of today's auto focus cameras to take the guesswork out of flash photography. Just mount the 34iAF in the camera's hot shoe and turn it on. Communication between the camera and flash begins immediately so the flash will operate perfectly with your camera for great flash pictures.