Canon Speedlite 580EX II Manual page 40

Using Fully Automatic Wireless Flash
Flash exposure compensation and other settings set with the master
unit will also be automatically set in the slave units. Thus, you need not
operate the slave unit(s). Wireless flash with the following settings can
be done in the same way as with normal flash shooting.
· Flash exposure compensation
· High-speed sync (FP flash)
· FE lock
With FE lock, if even one Speedlite will result in underexposure, the <Q>
icon will blink in the viewfinder. Open the aperture more or move the slave
unit closer to the subject.
Setting the Communication Channel
If there is another Canon wireless flash system nearby, you can change
the channel No. to prevent signal confusion. Both the master and slave
units must be set to the same channel No.
40
· FEB
· Manual flash
· Stroboscopic flash
Press the <G> button
1
so that <w> blinks.
Set the channel No.
2
Turn the <9> dial to select the
channel number, then press the
<8> button.