What I would like to do
600EX or ST-E3 on camera, Cells IIc on a bracket or similar. using 5D3.
I think a hot shoe from PC port should trigger the Cells IIc but will I be able to use H sync mode?
How would I best set this up?
The Cells IIc has to have the hot shoe connections to get the FP-sync signal.
I've done some testing with YN-622 as the on camera trigger with 600EX-RT on top and then the Cells IIc on a YN-622 receiver.
Doing it this way eliminates the 600EX-RT/5DIII benefits since the YN-622 is the master.
For x xync with pass through to the 600EX-RT use the Strato II multi from Phottix.
The 600EX-RT or STE3 on the transmitter on camera will work as normal, even when the transmitter is turned off.
However, even if the shutter speed is raised above x-sync it fires at x-sync when there is a Cells-IIc in the receiver.
So far, the only options for FP-sync with both speedlites and Cells-IIc has been an ETTL triggering system such as YongNou, Phottix, Pixel, or Pocket Wizard.
They all are 580EX-II based ETTL technology so the 600EX-RT becomes a 580EXII with a built in radio.