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Occasional Contributor
Posts: 17
Registered: ‎11-14-2012

Custom function setting on 600 EX RT with external battery pack

 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.

Frequent Contributor
Posts: 63
Registered: ‎11-24-2012

Re: Custom function setting on 600 EX RT with external battery pack

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.



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