Fire compatible Speedlite flashguns over distances of up to 30m Radio-frequency control provides reliable operation even when direct line of sight is not possible Radio frequency remote flash trigger Fire selected Speedlites from 30m away Part of the E-TTL II flash system Controls up to 15 flashguns Remote camera triggering Weather sealed against dust & moisture A radio-frequency flash trigger aimed at professional photographers using off-camera flash Reliable off-camera flash control Control compatible Canon Speedlite flashguns over distances up to 30m 24 G Hz radio frequency triggering operates reliably even when shooting outdoors & around corners – direct line of sight not required Multiple flash photography Create intricate multi-flash lighting set ups triggering up to 15 Speedlite flashes with a single camera-mounted Speedlite Transmitter ST-E3-RT E-TTL II flash metering makes exposure control easy Remote camera control Trigger an EOS camera fitted with a Speedlite Transmitter ST-E3-RT from a second unit or from a compatible Speedlite flashgun such as the Speedlite 600EX-RT Up to 15 cameras can be triggered at once for synchronised shooting Easy to use design The Speedlite Transmitter ST-E3-RT is sealed against dust & moisture to the same degree as professional EOS cameras & L-series lenses It features an easy to read back-lit LCD control screen & is powered by two AALR6 batteries