Agreed: Three is probably a practical limit for current CLS technology. At some point, with more than three remote groups plus an on-camera master engaged, the assorted preflash circuit delays will become intolerable as the milliseconds add up. Faster on-camera and remote unit circuitry and related technology are possible, but at what cost? At some point, consumers will refuse to pay it.
Without the four channel recording oscilloscope that I keep talking about, I am limited to the approximate scaling mentioned earlier in this thread for timing analysis, based on the 1/30 sec shutter time. The unknown here is how constant is my rotational velocity on the D2X capturing the preflash and image capture pulses.
I believe the preflash sequence functions asynchronously, given that a pulse from the on-camera master/commander is used to initiate the exchange with each remote group. The only truly synchronous interval appears to be that between the trailing edge of the image capture pulse and the simultaneous firing of the master and all remotes. This interval is short enough, that very slight differences between remote units (microseconds?) are not a problem.
Think how far we have come from the days of flash powder!
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