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I've got a Canon 580EX (original, not the II) flash, and now I'm interested in adding a slave flash. I stopped by a camera store this evening to look at the 430EX II, but the salesman advised me that:

  • an important difference between the xxxEX and xxxEX II flashes is that the latter uses a new communication protocol

  • due to the previous point, the 580EX won't reliably trigger a xxxEX II slave; it'll probably work some of the time, but it won't be dependable

  • ETTL only works with multiple 600EX RT units; lesser units don't communicate about exposure

  • most photographers use Pocket Wizards specifically because they preserve ETTL

All this came as quite a shock as I've always understood that a big advantage of Canon's system is that the body and Speedlite work together, etc. It seems unlikely that Canon would update their line in a way that's not backward compatible. So I went home and reviewed the manuals for the various units. It's pretty clear that the guy simply doesn't know what he's talking about on the third and fourth points; all the Speedlites seem to support wireless ETTL-II. But what about the first two points -- can I expect my 580EX to work well as a master with a 430EX II slave?

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1 Answer

Were you at BestBuy by any chance? It sounds like the guy wanted to sell 600EX-RTs. As far as I know, the optical sync system has never changed, at least in a compatibility breaking way. The new RT system supports some features that the optical system didn't support, but it only works between RT units which are currently only the 600EX-RT.

I don't have an older unit to test with, but I would expect that at worst, some control features that the newer flash supports might not be available, but I believe the basic firing protocol has been the same since the start of the system.

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It was Ritz Camera, actually. Thanks for confirming what I suspected -- that the 580EX should work fine. –  Caleb Jul 24 '13 at 14:11
I know that I can control my older 420EX with a 580EX II, so the protocol couldn't have changed to make it incompatible. –  Robin Jul 24 '13 at 17:23
@Robin - while I believe you are correct, I'd highlight that your test case doesn't prove anything as the system is one way communication, so a newer flash might send out data than and older flash ignores, but it could be possible for a newer flash to expect information that wouldn't be sent out by an older master flash, but it would be silly not to have the newer flash be able to fire on an older version of the protocol, and that's assuming there has even been any change or update. –  AJ Henderson Jul 24 '13 at 17:30
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