11-16-2012 04:45 PM
When using external battery pack with the 600 EX RT you will get better performance from the internal AA’s in the flash if you set Custom Function #12 on the flash to “ 1 “.
This will segregate the AA's from the recharge circuit when it is turned on.
The way that flashes are usually made is that they devote about 10% of the recycle to the flash when an external power source is connected.
This new Custom Function on the 600EX-RT overrides that when it is turned on.
12-07-2012 03:19 AM
C.Fn 12 is also in the 580EXII & 580EX plus I think the 550EX too, maybe even the macro flashes.
If all out fastest recycle speed is the aim, leave this set to 0, the flash will charge from the 8 AA's in the pack and the 4 AA's in the flash, however when they run out you have to change batteries.
If you set this to 1 then the flash charges from the 8 AA's in the pack only, the 4 in the flash run the display & electronics. What this means is that when the external pack is dead you can unplug it and get an assistant to swap out the cells, but you will still have 4 working AA's in the flash in case you need to react quickly. Personally I tend to use it this way as it's better for me to be able to react to a picture rather than have the absolute fastest recycle times. Though from 8 AA's the receycle is pretty fast.