Canon Speedlite 430EXIII-RT Instruction Manual page 96

Troubleshooting Guide
Radio Transmission Wireless Flash Shooting
Wireless shooting does not work.
When using a "Speedlite 430EX III", which is not equipped with the
radio transmission function, wireless flash shooting using radio
transmission is not available. Perform flash shooting using the
optical transmission wireless slave function.
The slave unit does not fire.
Set the master to <'M> and the slave to <'x>
(p.50).
Set the transmission channels and wireless radio IDs of the master
unit and slave unit to the same numbers (p.50-52).
Check that the slave unit is within the transmission range of the
master unit (p.46).
The camera's built-in flash cannot be used as the master unit in
radio transmission wireless shooting.
430EX III-RT does not support </> auto external flash metering (p.65).
The slave unit does not fire or unexpectedly
fires at full output.
Run the transmission channel scan and set the channel with the
best reception signal (p.52).
Position the slave unit at a location with possible clearest view of the
master unit.
Face the front side of the slave's main body toward the master unit.
Pictures are overexposed.
When using autoflash shooting with three firing groups A, B, and C,
do not fire with firing group C pointed toward the main subject (p.61).
When shooting in a different flash mode set for each firing group, do
not fire with multiple firing groups set to <a> or </>
pointing toward the main subject (p.65).
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