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Any updates for wireless issue with 600-EX-RT series and EL-1 Speedlites?


Does anyone know if Canon has addressed the wireless link issue with the RT flashes? I'm surprised Canon hasn't released some sort press release apologizing and acknowledging that their RT flashes no longer work anymore and that they are looking into some sort of fix or send in program?


Product Expert
Product Expert

Dear jhamm15,

Let's verify a few things if we could.

  1. Ensure that there is one unit configured as the sender, and the other units are configured to as receivers.
  2. Check that all the units are configured to use the same channel and confirm same wireless radio ID between the sender and the receiver units.
  3. Check that the sender unit on the hotshoe has a solid and consistent connection. Check that local, non-wireless flash use works properly with a unit on the camera’s hotshoe. Also, you can check to see if the sender and receiver can successfully test fire when the sender is not on the camera’s hotshoe but will later drop the connection.
  4. Please try using different channels. This is an attempt to eliminate RF interference in the local environment. Please note that different channels could be required in different shooting locations.
  5. If the above steps are correct and there are still issues can you try using the optical method to trigger the off-camera flash units if you're up to it.             

    If you are still experiencing issues once the above steps have been completed, are you able send your equipment into the FSC for investigation?

    • You would want to label your equipment. This can be done with anything from post-it notes to pieces of painter’s tape but whatever you use make sure  it is something that can be removed without marring the surface of the equipment. Each unit should be sent in as it was configured (do not change any settings or reset the equipment), and labeled with:
      • If the unit is configured as the sender or receiver.
      • The channel the unit is configured to.
      • If applicable, the group the unit is assigned to.
      • To reiterate: Do not reset/alter the equipment’s settings.
    • Please write up a description of the issue you are experiencing, including if you are using radio or optical triggering, the camera body being used (if not being included), distance between sender and receiver, and if possible, a description of the environment (are there radio or cell towers nearby, is the location residential or commercial, etc.).
    • Send the equipment to the Costa Mesa FSC. 


      Canon Factory Service Center
      123 Paularino Ave
      Costa Mesa, CA 92626-3311
    • Include all the flash equipment used.
    • If it has been verified that the flash equipment will drop connection even when not mounted on the hotshoe of the camera, including the camera body can be considered optional.

Product Expert
Product Expert

Hello jhamm15,

One other thing I wanted to mention is that equipment sent to the Factory Service Center will be inspected to see if cause can be determined. Once the inspection/testing is completed, we will provide you with an update, or repair as necessary.


I'm currently still performing experiments when I can.  I have six 600 EX-RT units (original version) along with the original version 1 of the ST-E3-RT.  I have not updated firmware at all on any of this equipment over the years.

The first time I witnessed the constant link dropping was a couple months ago.  All times prior (granted, I only do flash work a few times a year) worked a-ok.   I was outdoors in my backyard at the time.  Four flash units were in a deep 43" umbrella and my camera was within 8 feet of them.   Constant drops of at least 3 of the four units.  Had to cycle the power on flashes as well as the ST-E3-RT.  Could maybe take a couple shots and then no more until I cycled power again.

I tried to think of what the cause could be; my best guess being some type of interferance.   Other than the equipment being older, I have on my person an Apple Watch and iPhone.  iPhone is the latest model and Apple Watch updated every other year.

The other day in my office, also had one link drop.  But couldn't replicate it.  This I found odd as the amount of WiFi traffic in my office is massive and I had on my person the same watch and phone.

If I get any closer to figuring out what may be causing this, I'll be sure to write up a post on these forums.

Question for you... did the flashes always exhibit the dropped connections for you?  Or did they previously work well and then some date later, started to fail more often?

Going out on a complete limb, but perhaps its due to more cell towers in areas as compared to years ago?  More folks in general having WiFi in their homes if shooting in residential areas?


EOS 5D IV, EF 50mm f/1.2L, EF 135mm f/2L, 600EX-RT (x6), ST-E3-RT
EOS C70, RF 24-70 f/2.8L IS, EF-EOS R 0.71x


Yes this started happening somewhat last season, and now this year the RT wireless system barely works or sometimes at some event/venue spaces will not work at all. I have been using the RT flashes since around 2013, and they used to work solid and worry free. It must be cellular 5G rollout or newer WI-Fi technology? There was a wedding I did last year in Hartford, CT, Bond Ballroom which is an event space on the top floor of a high-rise, and i’m pretty sure there were cellular antennas on the roof. My flashes were going crazy with green link LED and the flash ready icon on each channel pulsing on and off. First time I ever saw that, or had a major reliability issue with my 600-ex-rt flashes. Fast forward now and I plunked down $3,000 on 3 of the new EL-1 and they just don’t work wirelessly.

Found video on my phone of this weird incident. It is a Yongnuo trigger, but this happened on my Canon 600ex-rt sender flash as well that night. Never had issues with the YN-E3-RT II trigger in the past, everything used to just “work” in the past. 

Thanks for this additional info.  It does seem like the issues are tied to increasing interference from extra tech everywhere.

Definitely a bummer to hear that the newer EL-1 units have the same issues.  I don't know though if this is perhaps a hardware issue (vs say something that could be tuned with firmware).   Here's hoping Canon makes their radio communications more solid going forward.

It would be quite expensive, but I may try an experiment in building a copper mesh box where I could have both the camera with transmitter and a few flashes inside it.   The mesh should sheild external RF signals.    Then, just a matter of finding a location where the problem occurs repeatedly, then put things in the box and try to replicate.   Such an experiment would then really point to external RF being the culprit.


EOS 5D IV, EF 50mm f/1.2L, EF 135mm f/2L, 600EX-RT (x6), ST-E3-RT
EOS C70, RF 24-70 f/2.8L IS, EF-EOS R 0.71x

Not applicable

Has anyone tried turning off their cellphones when this link drop occurs (as a test)?


Have done all of the trouble and more as listed above.

I bought 5 600’s and 2 ST-E3 RT Transmitters.

use all of the above with 2 Gripped 5D Mark III’s for over ten year with no issues at all. January 2023 “Link Drop” 

Now any situation, combination of units paired with a transmitter, “Link Drop” within two to five minutes. Wouldn’t interference block from becoming “Linked”?

had units sent to VA service and repair to have Firmware updated, only to have the Transmitters updated as they are now sender not Master..

regarding “Link Drop” still happens….

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