Canon EOS Rebel T3i 18-55mm IS II Lens Kit - Manual (Page 197)

197
Custom Wireless Flash Shooting
The built-in flash can also be added to wireless flash shooting explained
on pages 195-196.
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.
1
Basic settings:
Flash mode : E-TTL II
E-TTL II meter. : Evaluative
Wireless func. : [0+3]
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.
Fully-automatic Shooting with the Built-in Flash and
Multiple External Speedlites
A B
[1All and 2] [1 (A:B) 2]
COP
Y