Canon EOS REBEL T4I Instruction Manual page 37

Custom Wireless Flash Shooting
Fully Automatic ShOoting with the Built,in Flash and
Multiple External Speedlites
The built-in flash can also be added to wireless flash shooting explained
on pages 231-232.
The basic settings are shown below. By changing the [Firing group]
setting, you can shoot with various wireless flash setups of multiple
Speedlites complemented with the built-in flash.
Basic settings:
Flash mode : E=TTL U
E-TTL II meter. : Evaluative
Wireless func. : [_+-:--_ ]
Channel : (Same as slave units)
2
Select [Firing group].
®_Select the firing group, then set the
flash ratio, flash exposure
compensation, and other necessary
settings before shooting.
[_AII and _] ["_ (A:B) ,_]
233