From an evening spent messing around with Custom Function (CFn) settings on the 5D and 430EX, here’s a summary of behaviours:
| 5D 1st curtain (CFn.15=0) | 5D 2nd curtain (CFn.15=1) | |
|---|---|---|
| 430EX 1st curtain E-TTL mode 5 pin connection |
Pre-1st curtain metering flash1 1st curtain main flash |
Pre-1st curtain metering flash1 1st curtain main flash |
| 430EX 2nd curtain E-TTL mode 5 pin connection |
Pre-1st curtain metering flash1 2nd curtain main flash |
Pre-1st curtain metering flash1 2nd curtain main flash |
| 430EX 1st curtain Manual mode 5 pin connection |
No metering flash 1st curtain main flash |
No metering flash 1st curtain main flash |
| 430EX 2nd curtain Manual mode 5 pin connection |
No metering flash 2nd curtain main flash |
No metering flash 2nd curtain main flash |
| 430EX 1st curtain Manual or E-TTL mode 1 pin connection |
No metering flash 1st curtain main flash |
No metering flash 1st curtain main flash |
| 430EX 2nd curtain Manual or E-TTL mode 1 pin connection |
No metering flash 1st curtain main flash |
No metering flash 1st curtain main flash |
1 NB: The metering flash is a short burst from the main flash tube, and so is a very noticeable white light (indistinguishable from a proper flash firing if in front of the camera) and not a pulse from the red AF unit. Note that fast reacting subjects, especially if close to the camera may start to reflexively blink as soon as the pre-flash burst begins.
Setting CFn.07=1 (disable flash) on the 5D is helpful when combined with 430EX CFn.04=0 (emit AF assist) as the flashgun now functions as a low-light focus assist unit for ambient light photography in low-light conditions.
From experiments with a 720nm filter, I am not convinced that the AF-beam from the 430EX is infra-red as stated in the manual, but simply a dark red visible LED.