I haven’t posted for awhile. I’ve been busy with more demanding tasks.
I think I’ve done enough research into the Canon ETTL interface and I believe I now can build a prototype that connects to the Camera and provides control of one or more additional flashes, wired or wirelessly, including other Canon ETTL flashes. My understanding is that the Canon flash IR mechanism doesn’t really work too well (high noise, low range, etc.), and this interface would potentially allow the use of RF for communication and allow >4 ETTL flash units over a larger distance. I believe my solution should have a interface that connects to the camera’s ETTL hot-shoe (call it the “master”) and a remote interface that provide an effective ETTL hot-shoe for connection to each flash (call them the “remotes”) you want to control. The master would be able to set the different remote flash intensities and control remote flash occurrence. I don’t see any reason for limiting the number of remotes other than the user interface on the “master” to setup the different remote parameters. This interface should also allow the high-speed sync mode to work correctly with the camera for any flash.
This would be similar to the commercial pocket wizard, but would take advantage of the ETTL interface and ETTL flash controllability.
I hope to finish the prototype soon.