Canon EOS 70DN Basic Instruction Manual page 362

3 Setting the FlashN
2 Flash exposure compensation
Wireless functions
198
The same setting as step 3 in "Flash
Exposure Compensation" on page 190
can be set.
With wireless flash photography (via
optical transmission), you can use the
built-in flash to control an external
Speedlite.
For details, see "Using Wireless Flash"
on page 203.