Ok, I'm confused.
1. Can a 600EX-RT control a 580EX II (optically)? And, the reverse?
2. Can an ST-E3-RT control a 580EX II?
3. Can an ST-E2 control a 600EX-RT?
When I say, "control", not just trigger but pass E-TTL information?
I keep reading that the ST-E3 will only work with the 600EX-RT. Does that really mean Canon has no way to allow any interoperability with their previous flagship 580EX II?
Maybe they should come out with an ST-E4-RT/O...............one that could control the 600EX & the 580EX II
But, do I also understand that the Yonguno 622C's actually can control both the 600EX and 580EX II with E-TTL data? (A 622C on camera, a 622C on a 600EX-RT and also a 622C on the 580EX II)
Seem strange if I'm correct that the ST-E3-RT wouldn't have been designed to work with the 600EX-RT (probably RT) and 580EX II (optically)?
Or, is this why I see a lot of 580EX II's being sold? Does this imply most are going to the new RT control?
If this has been discussed before, please just point me to a better thread or documentation that explains the interactions/capabilities.