The Viper Wireless Group Flash Trigger for Canon Cameras from hahnel provides multi-group wireless flash control to Canon cameras. It operates with a 2.4 GHz frequency with a range of 328'. The system uses Digital Channel Matching to quickly and reliably connect up to three groups of receivers with a transmitter and avoid interference from other devices.
Flash output can be set via the transmitter for each group from 1/1 to 1/128 with intermediate stops of ±0.3 and ±0.7 for more exacting control over your lighting. This is all shown on the transmitter's backlit LCD display. Additionally, a manual mode is available for setting options on the flash itself and there is a pass-through hot shoe on the transmitter for TTL control of a mounted flash.
The receiver features both 2.5mm and mini-USB ports for connecting to flash units and the mini-USB ports on both units can be used for external power or firmware updates. Both the transmitter and receiver unit runs on two AA batteries.