Hello, photographer!

TL;DR: Random unlinking in radio transmission mode while using OCF is a known problem within the Canon flash system and is likely related to a wifi device causing interference with some venues being worse than others. Switch to optical mode when you encounter this (rather than radio mode) and see if it works.

Welcome to my deep dive on a super niche topic. Because wedding photographers are mainly self-taught and the settings we all use are very customized – it can be hard to find someone who runs their system the same as you! And when that system starts to act up or fails in seemingly random situations – it’s even more difficult to troubleshoot. A system that has worked for me for seven plus years started to become unreliable.

You probably found this page because you Googled “Canon flash unlinks” or “Canon flash disconnects after a few minutes” or “Canon wireless flash problem” or “600 EX II-RT drops link.” This problem is on the rise.

What basically happens, in plain English, is that you set your flashes up at home or studio (600 EX II-RT) using radio transmission and they work perfectly. You take test shots. Great.

You then go to a wedding/on location and it doesn’t work!

Sure, it works at first, but then when there is a pause in action of more than just a few minutes, the flash unlinks and shows red on the link indicator.

It might happen at a critical time (bride coming down the aisle, reception intros, champagne spraying night shot). Now you are limited to on-camera only. You get through the reception and go home and troubleshoot – working fine. Hmm, maybe a fluke. Maybe my batteries weren’t charged great.

So you then go to the next wedding. Flashes seem to work! Great! You leave the wedding thinking that solves it.

You go the next wedding. Now you can’t take any off-camera portraits in the church. It just will not work. It’s a winter wedding at night. You go outside the church in the snow and flash is firing perfectly.

You go to a venue and it works perfectly. You go there two weeks later and it won’t work. You go back another two months later and it works perfectly. A year later? Won’t work.


Another thing that may seem to happen is the on cam flash will repeatedly overheat and stop firing especially in ETTL mode while the off cameras unlink.

Sometimes only the ON camera will fire, sometimes NOTHING will fire.

At one wedding, the flash would disconnect every time I walked by a certain pillar (light turned from green to red back to green). The sender/receiver light will sometimes will disconnect if I do a vertical shot. Sometimes the light is still green on the sender but red on the receivers.

Sometimes they will reconnect themselves if I move around but MOST times I have to walk over to the off cameras and turn off my on camera flash, turn off the off camera flashes, turn the off camera flashes back on then turn the on camera back on.

Years ago, if I left the ballroom and went outside, sure, the flashes would disconnect but reconnect immediately when I returned. Not anymore in certain venues.

Once set up/fixed, it will work for 2 shots or 2 hours, but sometimes disconnect.

The chain will be working, but if there is a lull/lag before the bride goes down the aisle or the reception intros start – it stops working.

Multiple ppl have had this issue on Reddit and on the Canon forums. I’m attaching links below:


You try moving the flash. You mess with the ID numbers.

I tried buying all new flashes for $1500 to fix the issue. I bought all new batteries. I bought new chargers. I made sure the hot shoes were tight. I switched my on camera flash to manual mode (instead of ETTL in Grp Mode, which is my preferred style) because sometimes that seemed to fix it and they would all fire together. But the issues seemed to increase in frequency. A certain venue has an all glass wall – could that be it? Making the flash overheat?

Another venue has a big steel beam in it – flashes won’t fire on one side of the wall. Could that be it?

I went to a venue on Tuesday, flashes worked perfectly. Saturday, when the hotel was busy and the venue was filled with people – the flashes didn’t work.

Should I switch flash systems to Godox? I saw on certain forums/Facebook groups that they also have this issue too occasionally (and other issues) Should I switch to Profoto?

What about updating firmware on the flashes?

Should I send the camera in for repair? The flashes themselves? Use external battery packs?

“You should be using Auto for best channel, you should be scanning for best channel every time you change locations, you should be choosing your channel, changing channel does nothing. Use Channel 13.” I’ve heard it all.


I first noticed this issue in 2021 – but finally felt compelled to start Googling and really diving in as it increased more and more throughout 2022 and 2023.

I am no technology expert, but what I THINK is happening is that there is interference from somewhere. It can be a venue’s router, lights controlled by the DJ wirelessly, the photobooth, any kind of interference and with more and more electronic devices out there, the problem may continue to increase.

One photographer was having this issue at his studio of all places. The culprit there was an Apple Home Mini and once unplugged, the flashes began to work properly.

There are also rumors of a Canon rep saying to just move locations if it doesn’t work – which as a wedding photographer won’t work!

Canon has said they are aware of the problem and possibly working to fix it. People have reported the issue with the new flashes Canon has out as well – it’s likely a system issue and not a specific model of flash issue from what I can tell.


Here’s what I have been doing/following to (mostly) solve the issue.

One, I scout venues every single week. I go to the venue and use my flash set up. I allow enough time to have the flashes naturally go to sleep. I see if they stay linked. This is no guarantee they will work on the wedding day due to interference from other vendors and equipment brought in that day – but it helps! I am more prepared.

Secondly, when I encounter an issue, I put all the flashes into optical mode instead of radio. This is a big difference in my settings (and only one set of settings can be saved in the memory of the Canon flashes) so I wrote down the instructions and practiced them several times, doing it as fast as I can. I also have the instructions to do this written on my work armband in case I blank/panic – I just need to follow those steps.

For me, I run my normal wireless flash set up like this:
On cam – ETTL (to accommodate for subjects moving toward and away from me)
Off cams – each separate group – I choose the power – typically around 1/64th – I prefer to set manually as rim light/background separation light.

When I need to, I then turn off the firing on the on-cam to have images lit JUST by the off cam and vice versa.

You can replicate this in optical mode by having each flash in their own group in optical – it seems to work fine.

Where this will not work is taking say, a photo from outside to inside of the couple lit by an optical flash behind them when there is glass and walls between us. That’s fine, I can make it work – I have other ways to light for that rare situation (continuous).

I HAVE heard of this optical trick not working for a photographer at a certain venue here in Pittsburgh – but for me, this has worked almost all of the time.

When you encounter a flash problem, write down the venue and any details you can remember (DJ, lighting, etc) – you may start to see a pattern. I now KNOW of a certain venue where it always happens and have contingency plans for there and am happy to report that my optical workaround worked perfectly there.

My further contingency plan is to switch to Profoto – but I love the small size and ease of the Canon units and the quality I get from them plus I love having everything as a Canon system, so I’m not going that route yet!

I hope this helps – feel free to drop a comment or connect on socials if you are encountering this issue!

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