Canon EOS 1D X Mark II - Manual (Page 89)

89
Positioning the Cameras
 If focus cannot be achieved with autofocus, linked shooting is not
possible with the corresponding slave camera units.
 Do not use multiple flash units. Although slight, there is a difference in
the shutter release timing which may cause out-of-sync flash firing and
inadequate exposure.
 Linked shooting is not possible when the slave cameras are set to any
setting other than [Mirror lockup: Disable], or when the Live View
shooting/Movie shooting switch of the master or slave camera is set to
<k>.
 During linked shooting, when you press the AE lock or depth-of-field
preview button, the camera adjusts the focus and meters as if you had
pressed the shutter button halfway.
 Once you have established a connection between the master camera
and slave cameras, the settings are retained even after you replace the
batteries.
 If you will no longer use a slave camera in linked shooting, set
[Connection settings] to [Disconnect] on that slave camera.
 Any cameras compatible with linked shooting, when they have WFT
series transmitters attached, can be used as slave cameras, regardless
of model.