Canon 5D Mark III and Flash charging when reviewing photos Home » Forums » Photography » Lenses

My second letter to Canon was:

Thanks for some useful information not related to my question.

You wrote "Whenever you have a Speedlite on the camera, it will try to refresh its charge"

and this should be true EXCEPT when the 'Review Photos' button is pressed, as was the case on the 5D Mark II.
Just last night I spent twenty minutes looking through my photos, not noticing my flash was forced on the whole time. Dead batteries the next day. But the main problem is always having to turn on/off the flash in the field to review photos while waiting for wildlife. Again, not true with the 5D Mark II.

And Canon did not have a useful response, which is included here in part. I had hoped for a firmware fix.


Thank you for taking the time to reply. I understand that you are concerned about your flash charging the capacitor while waiting for your next shot. I can address this.

You would need to do it one of two ways. You can save battery power by setting the auto sleep mode on the flash, however, when it wakes back up you would have to wait a few seconds for the flash to charge up before you fire. Or you can leave the sleep option off and the flash will wait charged and ready to fire, which in turn would drain the battery.

The sleep setting would be a Custom Function on the flash. For the Speedlite 580EX it is C.Fn 04, for the Speedlite 580EX II it is C.Fn 01 and for the 600EX RT it is also C.Fn 01.