Canon 600EXII-RT Instruction Manual page 87

Setting the focus mode switches of the lenses attached to the slave
cameras to <MF> and taking the picture with manual focusing is
recommended. If focus cannot be achieved with autofocus, linked
shooting is not possible with the corresponding slave camera units.
There is a short time lag between the release of the slave camera unit
and the release timing of the master camera unit. Perfectly simultaneous
shooting is not possible.
You can fire the Speedlite during linked shooting when P.Fn-06-1 is set
(p.119), but the appropriate exposure may not be obtained or uneven
exposure may result if you fire multiple Speedlites simultaneously during
linked shooting.
When [Flash firing] in [External Speedlite control] or [Flash control]
is set to [Disabled] (p.54), linked shooting cannot be performed.
If performing linked shooting is not possible with a Live View image
displayed and P.Fn-06-0 set (p.119), set [Silent LV shoot] on the master
camera unit menu to [Disabled]. If [Mode 1] or [Mode 2] is set, the slave
camera units may not be released depending on the camera model
used.
The transmission distance may be shorter depending on the conditions
such as the positioning of slave flashes, the surrounding environment,
and weather conditions.
The linked shooting function is the similar function as the linked shooting
featured by the WFT series of wireless file transmitters. However, linked
shooting cannot be performed in combination with the WFT series file
transmitters. Moreover, the release time lag differs from linked shooting
performed using the WFT series.
Linked Shooting Using Live View Function
Linked shooting in Live View is not possible when a Speedlite set to P.Fn-
06-0 (p.119) is attached to one of the cameras below and set as the master
camera unit.
Perform linked shooting after switching Live View shooting to viewfinder
shooting or set the Speedlite to P.Fn-06-1.
EOS REBEL T6S/760D, EOS REBEL T6i/750D, EOS REBEL T5i/700D,
EOS REBEL T4i/650D, EOS REBEL T3i/600D, EOS REBEL T2i/550D,
EOS REBEL T1i/500D, EOS REBEL XSi/450D, EOS REBEL XS/1000D
Linked Shooting with Radio Transmission
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