The term TTL literally means ‘through the lens’ and stands for the light metering mode and flash duration of an SLR camera, which operates ‘through the lens’. Digital SLR cameras (DSLR) use a slightly different way of measuring the surrounding light and now days this light measuring mode is called iTTL (Nikon) and eTTL (Canon). TTL will measure the surrounding light and will send the necessary information to the strobe to allow a precise flash duration that will produce a perfectly exposed shot.

Digital SLR cameras use a digital TTL protocol (iTTL and eTTL) which does not match the older ‘analog’ TTL protocol of most underwater strobes. Therefore an electronic ‘translator’ is required to translate the camera’s eTTL or iTTL protocol into an analog TTL protocol. Hugyfot housings can be equipped with such a TTL converter which allows the use of most ‘analog’ TTL underwater strobes in combination with a digital camera. Note that there are underwater strobes available which already have a built-in TTL converter.