5D Mkiii problems with multiple 600EX-RT's

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The Stal
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5D Mkiii problems with multiple 600EX-RT's
2 months ago

Hi everyone. I've looked everywhere for people having the same issues as me but have found nothing so here goes...

I am a professional wedding photographer using two 5D Mk3's and 600EX-RT's. For receptions I use two off camera (with Bolt battery packs) and one on camera. On camera set to E-TTL, both off cameras in manual mode. On the master flash I use Group mode.

For several wedding in a row now I will have all three flashes not fire when I'm shooting in somewhat rapid succession. It's most noticeable during bridal party introductions. (I'd say one shot every 1-3 seconds). Sometimes it's every other shot, sometimes it's a couple of shots in a row. Sometimes it will fire 2 or 3 times in a row and then not fire.

I've tried with both cameras using a different flash as the master. No difference.

Firmware is up to date.

Off camera flashes are set to draw power from the pack in the custom function menu.

I manually scan and set the channels. They're full signal (and not too far away generally)

Custom channel ID's (not that it matters)

I've talked to Canon and the guy didn't know what to tell me. If it was a signal problem the on camera flash should still fire. When they don't fire it's always all of them, not just one or two. I'm pretty sure it's not a recycle problem. I put fresh batts in for the reception. I've tested this at home and can not re-create the problem. They all work flawlessly.

I also seem to have no issue when just using the on camera flash solo not connected to the slaves.

I do use rechargeable batteries. (Watson, Duracell and Energizer) and I also shoot to the SD card as well as the CF card. Usually both MRAW. (I know the SD card slot limits speed)

It seems it's a camera to master flash communication problem. Is it possible that the slow buffer speed is blocking communication somehow to the flash?

I can't believe it has to do with the rechargeable batteries. If I wait longer between shots the flashes are a lot more consistent. They then fire 95% of the time at least.

Has anyone had this issue? If it's happening with different flashes on different bodies it has to be something with the camera?

Thanks in advance for any input.

Canon EOS 5D Canon EOS 5D Mark III
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