The Canon ST-E3-RT Speedlite Transmitter can help you take full advantage of all the features on Canon's Speedlite 600EX-RT and 430EX III-RT flashes. The ST-E3-RT makes complex lighting setups simple by facilitating radio-controlled, two-way wireless transmission up to 98.4' away, among up to five groups or fifteen individual Speedlites. It has controls similar to the Speedlite 600EX-RT, including multiple flash metering options, and a variety of flash modes. Compact design with highly reliable construction combined with a clearly laid-out information panel and buttons with back lighting make this an indispensible tool for advanced professional flash photography. The ST-E3-RT represents the next generation in wireless flash systems.

Note: Because it does not have an optical transmission function, the Speedlite Transmitter ST-E3-RT is not compatible with earlier Speedlite models such as 580EX II.

Newly-designed wireless system uses 2-way radio wave communication for enhanced communication among master and slave units. Achieves a transmission distance of up to 98.4' (30 m), all at a 360 degree angle.
Up to 5 groups, or 15 individual flashes can be controlled via 1 transmitter.
Supports E-TTL II flash, manual flash, stroboscopic and auto external flash metering.
Dot matrix LCD panel displays all pertinent information simultaneously and backlit control panel means easy operation.
8 types of custom functions, 3 types of personal functions.
Improved hot shoe contacts for more reliable information transmission and operation.
Slave operation confirmation:
Green Light--Lit: Radio Transmissions Okay
Red Light--Lit: Not Connected
Blinking: Transmission Error/ Too many units
Orange Light--Lit: Sub-master transmission
Blinking: Receiving remote release shooting, linked shooting signal
Not compatible with earlier Speedlite models such as 580EX II