TTL, E-TTL, i-TTL, ...

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TTL, E-TTL, i-TTL, ...

Digital SLRs do not use the conventional Nikonos TTL protocol, but use their own proprietary version like E-TTL (Canon), D-TTL and i-TTL (Nikon, Fuji). These cameras can generate multiple pre-flashes (sometimes up to 15) as well as a pre-flash with an extended duration. Standard TTL strobes are therefore not capable of working with these cameras. In order to work with these TTL protocols, conversion equipment is required or strobe manufacturers should support them in future models. The Sea&Sea YS-55TTL/E strobe has got Canon E-TTL support and Ikelite is also working on their DS-50 and DS-125 flash systems to support digital TTL protocols (read the Ikelite E-TTL article for more information).

Auto TTL

Some strobes, like the Sea&Sea YS-90Auto for example, offer a special slave mode that claims to automatically adjust the power output to the conditions. This method is based on setting the camera's aperture on the strobe, and the strobe matching its output by measuring the ambient light with its own meter.

This mode may not always be usable given the fact that not all compact cameras show the aperture to the user (nor allow manually setting it). Furthermore, the position of the strobe may cause it to measure area with different brightness than the camera is looking at, and thus still producte over or underexposed photos.

S-TTL / DS-TTL

Strobes such as the Sea&Sea YS-110 TTL and the Inon D-2000 offer these optical slave-TTL types. With S-TTL (Optical Syncro TTL) and DS-TTL (Digital Slave TTL) the external strobe not only watches the start of the camera's internal flash, but also when it stops. When the camera has determined the proper amount of light for correct exposure has been received, it will stops its strobe and therby also the external strobe indirectly.