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Speedlite EXII-RT: RF control to the remote Speedlites failing

Question for photographers who use lighting ("flambient"), not HDR...
I use as many as 4 Canon 600 EXII-RT Speedlites for interior photography. One on camera as the Master controlling the other flashes, as required, using RF. I use the other Speedlites to light adjoining rooms and spaces so they don't appear as dark spaces in the photo. It has been a great system, but lately the RF control to the remote Speedlights has been failing and I spend way too much time resetting them (turning them off and on).
Any suggestions would be greatly appreciated.
#Speedlite 600 EXII-RT

Product Expert
Product Expert

Hi jmaurophoto,

I'm sorry to hear your speedlites are losing their radio frequency connection. There are a couple of things to try with an issue like this.

The first thing would be to load new batteries in all of the flashes to see if the same thing happens. If the batteries in one of the flashes are losing charge, or are unable to provide power as well anymore, it can cause the full group to lose connection. It would be best to try new batteries for this rather than trying recharged batteries. Overtime as batteries are recharged multiple times they can lose the ability to hold as much charge and that can cause issues like this as well.

The other thing is that there could be interference on the channel you currently have all the speedlites set to. We would recommend having the transmitter flash do a channel scan to see which one has the strongest signal. Then set all the flashes to that channel to see if the same thing happens. Information on how to do a channel scan is on page 65 of the speedlite manual. If you need a copy of the manual it is available HERE.


Hello Hazel. Thanks so much for staying on this. I always use charged freshly eneloop batteries. The ones that I am using are fairly new. I will try new alkaline batteries and see if that helps. I have been using the scan feature in an effort to find the best signal. Just yesterday I was experiencing the same thing. I had to reset each of the flashes for nearly every photograph. I waste more time doing that. It means my time on site is nearly doubled. I will try fresh alkaline batteries, but I honestly don't think that will work. It's so aggravating and frustrating because they used to work great. Thanks again.

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