Canon EOS R6 Mark II Mirrorless Camera with 24-105mm f/4-7.1 Lens - Manual (Page 214)

Non-Canon Flash Units
Sync speed
Sync speed for non-Canon compact flash units varies by shutter mode.
[ : Shutter mode] Setting Sync Speed
Mechanical 1/200 sec. or slower
Elec. 1st-curtain 1/250 sec. or slower
With large studio flash units, the flash duration is longer than that of a compact flash unit
and varies depending on the model. Before shooting, confirm that flash sync is
performed correctly by taking some test shots at a sync speed of approx. 1/60 sec. to
1/30 sec.
Caution
Using the camera with a dedicated flash unit or flash accessory for cameras of
other manufacturers poses a risk of malfunction and even damage.
Do not attach a high-voltage flash unit to the camera's multi-function shoe. It may
not fire.
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