Canon Speedlite Transmitter ST-E3-RT

Off-camera flash transforms portraits and events, and radio makes it dependable. The Canon Speedlite Transmitter ST-E3-RT mounts on the camera’s hot shoe and controls Canon’s RT-series Speedlites by radio, so flashes hidden behind softboxes, placed around corners or used in bright sun still fire reliably at up to about 30m with 360° coverage.

It commands up to 15 Speedlites in up to five groups across 15 channels, setting E-TTL II, manual or stroboscopic output from one screen, with flash ratio control from 1:8 to 8:1 and high-speed sync on compatible cameras. Receivers include the Speedlite 600EX II-RT, 600EX-RT and 430EX III-RT, so it grows with a lighting kit.

Running on two AA batteries for around 10 hours of continuous use and weighing just 110g, it sits far lighter on the camera than a full-size flash used as a master. This is the original version of the transmitter; later versions added functions this model does not offer, so the features listed here describe exactly what you get.

Technical Specifications:

• Transmission: Radio, 360° coverage
• Range: Approx. 30m
• Channels: 15
• Groups: Up to 5
• Maximum Speedlites: 15
• Flash Modes: E-TTL II / E-TTL, manual, stroboscopic
• Flash Ratio: 1:8 to 8:1
• High-Speed Sync: Yes, with compatible cameras
• Compatible Speedlites: 600EX II-RT, 600EX-RT, 430EX III-RT
• Power: 2 x AA, approx. 10 hours continuous
• Version: Original (Ver. 1)
• Dimensions: 67.4 x 61.5 x 77.4mm
• Weight: 110g (without batteries)