Showing results for 
Show  only  | Search instead for 
Did you mean: 

Canon radio-controlled flashes failing in use - Senders and receivers disconnecting



I am spreading the news about the failure of communication between Canon "Sender" (Master) flashes and Canon "Receiver" (Slave) flashes.  Since around 2020 the communication between Master and Slave flashes can be broken by a public radio wave of some kind.  I’m not an EE, so I can’t tell you what the source of the problem is, but I can tell you that I have tested equipment all over the greater Seattle area, and about 80% of the time the Slaves disconnect from the Master in under 20 minutes of being turned on.   The shortest time to disconnect happens in 60 seconds with most disconnects occuring in 8-12 minutes.  I’ve only tested this in the greater Seattle area, but I suspect that if you are in a major urban area you will experience this failure.

I’ve tested this with Canon 600EX RTs and with a new R3, RL-5, and ST-E10, so it’s happening to the latest Canon equipment. 

You can read about what I’ve tested here:




I web-searched for "Canon flashes and 5G interference" and found a lot of material.

Results show only two Canon links, to threads on this forum, and many articles about 5G interference all over the place.

It seems that 5G causes problems with many portions of the radio spectrum. Canon flash is one victim that may be insignificant compared to the others.

Here's one of the papers:



Thanks for the info.  It is not insignificant when using these is how I feed my family. And the fact that Canon is commiting advertising fraud is also not insignificant.


Not trying to belittle your (and every other Canon flash system user's) problem at all.

Compared to problems with weather satellites, GPS and national security, and aviation altimeters, though,  I'd say general photography ranks low on the scale of critical international importance. Canon isn't the only victim of a a too-crowded radio spectrum with not-enough separation of apportioned frequency bands. Everyone has to be trying to figure this out.

This isn't helpful.  This problem has been going on for at least two, if not three years.  And over all the years of using electronic equipment that makes use of the 2.4 GHz band (10+ years now), only Canon's Speedlites have failed in these latter years.  All my other devices from Apple, Nintendo, Pioneer (to name a few) have not dropped communications like the flashes did for me during 2022 to 2023.

So clearly the onus is on Canon to address this.

Trust, is also an issue here.  I was a huge proponent of working with all Canon gear as much as possible to include lighting.  If this was something that was addressed say with the EL-1 and EL-5, I'd chalk it up as the 600-series just being too old.  And I'd be a-ok with that and suspect many others would agree.  But when the latest-gen of Speedlites have the same issues and there's no response from Canon, trust is eroded.

I predict that we'll see more and more photographers move to other brands.


Camera: EOS 5D IV, EF 50mm f/1.2L, EF 135mm f/2L
Lighting: Profoto Lights & Modifiers

Thanks for the link to the Congressional Research Report. It definitely supports the adverse findings many people have reported here in the Canon User Forum. There is no doubt the Canon RT Flash system is susceptible to Radio Frequency Interference. This appears to have started 2 to 3 years ago based on the timing and frequency of reports. Over the same timeframe there does not appear to be a similar trend developing for other brands.

The thing that is troubling is that Canon is surely aware of this issue now yet remains silent. Furthermore, they continue to introduce new and more expensive products into the market that use the same aging RT communications system which continues to demonstrate that it is unsuitable for its intended purpose, wireless communication and control.

As others have mentioned, I too have been a devoted Canon customer for many years. But I have to say this situation has shaken my faith in the brand and Canon's customer commitment. It casts a dark shadow on all their other products for me. It costs a company a lot of time and money to acquire a customer as any marketer will tell you. Once a loyal customer is lost, they seldom, if ever, return. Hopefully that won't happen here, and Canon will wake up and address their problem with this product family.

I still have faith in Canon in general and do indeed plan to keep using and purchasing their cameras and lenses.


Camera: EOS 5D IV, EF 50mm f/1.2L, EF 135mm f/2L
Lighting: Profoto Lights & Modifiers


The issue of “Link Drop” started for me last year at this time. 
Never had an issue when first bought in 2012 until last year.
5 600 EX-RT and 2 ST-E3 Transmitters. any scenario in any combination, 600 as a Master and others as slaves, one 600 or all 5, either Transmitter, change ID and Channels…….…

sent units into CPS for updated Firmware. Only transmitters updated as now Sender and Receiver. 600’s never updated…. ”you got it…. “ Link Drop”……

Now when going on sight with Fingers and Toes crossed.

there are lots of people in the same boat... which is sinking fast.  Very disappointing that even the new EL-5 and EL-1 suffer from the same flaw.


it is not likely that a firmware update could fix this problem. This is a hardware issue, not a software issue. Products have to be re-engineered to use radio frequencies that 5G won't interfere with.