The TTL Flash Commander for Canon from Geekoto is capable of sending 2.4 GHz TTL signals to control the flash at distances up to 164'. The Commander offers 16 channels and 4 groups for complex setups or to avoid interference from other shooters. It also supports High Speed Sync with shutter speeds as short as 1/8000 second to control bright backgrounds or shoot at wide apertures for shallow depth of field. The Commander also supports stroboscopic flash and provides +/-3 EV flash exposure compensation. The Commander is powered by two separately-purchased AA batteries.