Using Wireless Flash - Canon EOS 70D Instruction Manual

Using Wireless FlashN
The camera's built-in flash can work as a master unit with Canon
Speedlites with a wireless slave feature via optical transmission and
wirelessly trigger the Speedlite(s) to fire.
Be sure to read about wireless flash photography (optical transmission)
in the Speedlite's instruction manual.
Slave Unit Settings and Position
Regarding your Speedlite (slave unit), refer to its instruction manual and
set it as follows. The settings other than the ones below for the slave
unit's control are all set with the camera. Different types of Canon
Speedlite slave units can be used and controlled together.
(1) Set the external Speedlite as a slave unit.
(2) Set the external Speedlite's transmission channel to the same
channel as set on the camera.*
(3) If you want to set the flash ratio (p.210), set the slave unit ID.
(4) Position the camera and slave unit(s) within the range shown
below.
(5) Face the slave unit's wireless sensor toward the camera.*
Indoors
Outdoors
Example of Wireless Flash Set-up
Approx.
80°
1
Approx.
10 m
(32.8 ft.)
Approx.
7 m
(23.0 ft.)
Approx. 5 m Approx. 7 m
(16.4 ft.) (23.0 ft.)
2
203