Canon SPEEDLITE 580EXII Mode D'emploi page 40

The Speedlite's zoom setting will be set automatically to 24mm. It is possible to
change the master unit's zoom setting. However, note that the master unit
transmits wireless signals to the slave unit(s) with the preflash. Therefore, the
flash coverage must cover the slave unit's position. If you change the master
unit's zoom setting, be sure to test the wireless flash operation before shooting.
If the slave unit's auto power off takes effect, press the master unit's test
firing button to turn on the slave unit.
A test flash cannot be fired while the camera's operation timer 4 or 0 is active.
The slave unit's auto power off time can be changed. (C.Fn-10 → p.27)
The time during which the slave unit's auto power off can be canceled by
the master unit can be changed. (C.Fn-11 → p.27)
Master Unit's Flash ON/OFF
You can disable the master unit from firing so that only the slave unit(s)
will fire a flash.
Even if you disable the master unit's flash firing, it will still fire a preflash to
transmit wireless signals.
Press the <G> button
1
so that the display blinks as
shown on the left.
Disable the master unit's flash
2
firing.
Turn the <9> dial to select <Q>,
then press the <8> button.
The icon will change to <Y>.
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