Canon EOS 5D Mark III Instruction Manual (en)

 Flash Photography
With an EZ/E/EG/ML/TL-series Speedlite set to A-TTL or TTL 
autoflash mode, the flash can be fired at full output only. 
Set the camera’s shooting mode to <a> (manual exposure) or 
<f> (aperture-priority AE) and adjust the aperture setting before 
When using a Speedlite that has manual flash mode, shoot in the 
manual flash mode.
Sync Speed
The camera can synchronize with non-Canon compact flash units at 
1/200 sec. and slower speeds. With large studio flash units, since the 
flash duration is longer than compact flash units, set the sync speed 
within 1/60 sec. to 1/30 sec. Be sure to test the flash synchronization 
before shooting.
PC Terminal
The camera’s PC terminal can be 
used with flash units having a sync 
cord. The PC terminal is threaded to 
prevent inadvertent disconnection.
The camera’s PC terminal has no 
polarity. You can connect any sync 
cord regardless of its polarity.
Cautions for Live View shooting
If you use a non-Canon flash unit with Live View shooting, set [z4: 
Silent LV shoot.
] to [Disable] (p.208). The flash will not fire if it is set to 
[Mode 1] or [Mode 2].
Using Non-EX-series Canon Speedlites
Using Non-Canon Flash Units