Canon EOS 5D MARK IV Instruction Manual page 290

D Flash Photography
Non-Canon Flash Units
Sync Speed
The camera can synchronize with non-Canon compact flash units at
1/200 sec. and slower speeds. With large studio flash units, the flash
duration is longer than that of a compact flash unit and varies
depending on the model. Be sure to check before shooting if flash
sync is properly performed by test shooting at a sync speed of
approx. 1/60 sec. to 1/30 sec.
PC Terminal
Cautions for Live View Shooting
If you use a non-Canon flash unit with Live View shooting, set [z6:
Silent LV shoot.] to [Disable] (p.312). The flash will not be fired if it
is set to [Mode 1] or [Mode 2].
If the camera is used with a flash unit or flash accessory dedicated to
another camera brand, the camera may not operate properly and
malfunction may result.
Do not connect to the camera's PC terminal any flash unit with an output
voltage of 250 V or more.
Do not attach a high-voltage flash unit to the camera's hot shoe. It may
not be fired.
A flash unit attached to the camera's hot shoe and a flash unit connected to
the PC terminal can both be used at the same time.
288
The camera's PC terminal can be
used with flash units having a sync
cord. The terminal has locking
threads to prevent the cord from
falling off.
The camera's PC terminal has no
polarity. You can connect any sync
cord regardless of its polarity.