- Advanced Features: E-TTL Compatible Since it is compatible with E-TTL auto flash functions, groups of 550EX Speedlites are able to take advantage of High-Speed Sync, FE Lock, Flash Exposure Bracketing, and Pre-flash evaluative metering.
- Built-in AF-Assist Beam: The AF-Assist Beam automatically fires in low-light and low-contrast situations to assist the camera's auto focusing system.
- Sets and Controls Flash Ratios: Transmitter ST-E2 sets and controls all functions of its Speedlite 550EX slave units. Flash ratios,for example,are controllable between 2 Speedlite 550EX groups.
- High Speed FP Flash: High Speed FP (Focal Plane) flash for synchronization at all shutter speeds is available, even the EOS-3s top speed of 1/8000. Larger apertures can be used to obtain better background blur. And fill flash can be used for moving subjects in daylight. Weight:3.5 oz./100 g (Including battery).