The Canon Speedlite Transmitter ST-E2 is a dedicated E-TTL (II) wireless autoflash transmitter that can control an unlimited number of 420EX, 430EX, 550EX and 580EX flashes, in two separate groups; A and B.
The ST-E2 sets and controls all functions of its slave units. The flash output ratio between groups A and B can also be adjusted from 8:1 to 1:1 or from 1:1 to 1:8.
Under low-light or low-contrast conditions it emits an AF-assist beam linked to the EOS-3's 45 focusing points.
Note: 420EX/430EX can not be used as the master slave to trigger other flashes.
