The Speedlite Transmitter ST-E3-RT (Ver.3) provides continued support of Canon camera's that feature a standard hot shoe (not compatible with multi-function shoe equipped cameras). Many of the most popular features carry over to version 3, such as wireless rear curtain synchronization to capture ambient light trails and convey a sense of speed for moving subjects. An expansive minimum output range (down to 1/8192 power), and FE Memory as part of the radio transmitter so you can lock-in an E-TTL flash exposure level, even in complex multi-flash set-ups, and continue to use it for the same scene or subject. Radio controlled, two-way wireless transmission up to 98.4 ft., up to five groups or fifteen individual Speedlites, a dot matrix LCD with backlighting, intuitive controls and more.