Chapter 9: Working with Flash
When you pair the EOS 5D Mark III with the new Canon Speedlite 600EX-RT, or other Speedlites, a new world of light and control opens up. You have the option for wireless E-TTL (Evaluative Through-the-Lens) flash with radio transmission for multiple flash shooting. The radio transmission overcomes many of the previous restrictions of wireless optical flash, and it opens the door for much greater flexibility in the placement of Speedlites. Of course, if you have earlier Speedlites, then you can use optical transmission for wireless multiple flash photography with or without the Speedlite 600EX-RT.
The 5D Mark III enables you to control functions of the flash directly from the camera menu. You can set the metering, flash sync speed in Aperture-priority AE () shooting mode, flash exposure compensation, bracketing, shutter synchronization, flash ratio, and Custom Functions for compatible EX-series Speedlites.
Deciding Whether to Use Flash