TTL Converters & Flash Triggers
Getting the right exposure from your strobes underwater is essential. Sometimes that means you need an accurate exposure, and for quick sujects you need accurate timing. TTL converters and Flash Triggers help underwater photographers use their strobes effectively. A TTL converter is an electronic device that helps your camera communicate with your underwater strobe. TTL converters tell your strobes how to fire. It allows the strobe to accomplish the equivalent of "automatic mode" for a strobe. A signal is sent from the camera to the strobe through the TTL converter. The TTL converter "tells" the strobe the best exposure setting for the lighting situation and you end up with properly exposed photos. TTL converters by themselves are usually connected to the camera and strobe via eletronic sync cord.
Flash triggers, on the other hand, tell a strobe when to fire (i.e. they trigger the flash). Flash triggers usally send an LED signal to the strobe from the camera. When the shutter button is press, the flash trigger will instantaneously flash an LED optical signal. The optical signal travels through fiber optic cables attached to the outside of the housing and to the strobe which then fires. Flash triggers are great for underwater photographers who want the housing safety and convenience of using fiber optic cables, but don't want to increase recycle times due to a pop up flash. Using a flash trigger will let you fire as quick as the camera can fire. Therefor, you are only limited by your strobe's recycling speed and not your camera's. Most flash triggers can only be used when the strobe is in manual mode. However, some flash triggers are also TTL flash triggers. This means that they can be used with your strobes TTL mode. This allows the strobe to fire at the right exposure as well as quickly.