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600 EX II-RT's dropping signal



We are wedding photographers who have used Canon 600EX II- RT's for years now. We use them for receptions and lighting the dance floor, speeches, and creative shots. We have never had issues with connectivity until around 2019/2020. All the sudden since, it has been getting worse and happening at more and more venues. We have found our flashes will not stay connected via radio transmitters at certain venues. We do channel searches, place our flashes in different areas, etc, same issue. We will connect for 2 min, then it will disconnect out of no where. We use mainly another 600 EX II RT as the trigger (master) and other 600 EX II RT as slaves. We honestly are sick of it and are thinking of ditching Canon. We haven't heard of any other flash brands having any issues. Only hesitancy we have is that we have already 8 of these purchased from years of buying them and don't want to have to replace them all with a different brand. Has Canon came up with a fix for this or bettering their flash products? I see this is a known issue and it seems the only "solution" is use Line of Sight. Which won't work for how we use them most the time. ANY HELP PLEASE?


I think 2.4 is definitely over saturated in the past few years and now we are screwed. Canon needs to make a different option, otherwise I will definitely need to switch to another company soon 


Same exact issue with my Canon EL-1 flashes as well as 600ex first gen flashes. I called Canon CPS last week to complain finally and they acted like I was the only soul to have this issue. Wireless dropping started about the same years too. I’ve been using Canon RT system since around 2013 and used to work pretty decently. 

I went with Godox, no problem at all and a 4th of the cost.


So disappointing to see that this isn't a user error but a Canon gap in functionality. I invested in a 600EX for the purpose of being able to add remote flash to my camera bag (R6) and it is NOT reliable with the Canon ST-E3. This is a significant investment and unacceptable that Canon dismisses the problem. 

Dmbjo: It’s not just the ST-E3, it’s like all of canon’s RT flash eco system. It’s like Canon’s radio system is out of date and everything interferes with its RF performance. I swear it has to be like 5G cellular and/or newer Wi-Fi standards that drown it out. I had to switch to Godox Speedlites this wedding season for slaves (which is less than ideal). When I’m richer I’m gonna switch to Profoto’s A series speedlites. I still use my EL-1’s for on camera, but completely stopped using Canon RT because it is pretty much crippled now and useless.


I am experiencing exactly the same problem. I have an ST-E3-RT-II and three 600EX II RT's. I have tried all the suggestions I can find in this forum but so far there is no solution. I contacted Canon technical support yesterday about the issue. I was told Canon has very few reports of such behavior which I find surprising given the number of reports here in Canon's own Customer Forum and given the many reports I've seen elsewhere on the Web. I have been a Canon user for years but have to say this issue has caused me to reconsider my customer loyalty going forward. Does anyone have more recent information or know if Canon has acknowledged this issue?

Here is a YouTube video that shows exactly the issue:

I highly doubt any additional effort will be put into this issue, as these flashes and transmitter are being phased out. 

Not sure if anybody is experiencing this with the new flash and transmitter.

Agreed.  Things seem to be getting worse over time as well.  This past weekend, I experienced constant link drops in my basement which in the past has been a location that I hadn't experienced any issues.


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