5. Confirm wireless link. Confirm that the <LINK> lights on the 600 EX - RT’s are lit and green and that the AF- assist beam emitter on the receiver is blinking at 1-second intervals. Also confirm that the red flash ready light is lit on the sender unit.
Yet another Speedlite 600EX-RT and Speedlite Transmitter ST-E3- RT innovation is the ability to fire recent EOS cameras remotely, using either of these devices as a trigger. Remote control from your flash? Syl explains in this episode.