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

EOS R + Speedlite 600EX-RT & 600EX II-RT Flash going off but images are underexposed


Mid-session this morning, using double speedlites and a triggered flash (all Canon).  At one point, the photos were crisp and bright.  Flashes were working.  Next point, flashes continued to work, but the photos are not showing the result of a flash being used.    

Nothing changed in how I was taking the photos, but suddenly the photo output changed drastically.

Would this be a camera body issue or a speedlite issue?




What camera?

What flash?

What trigger and method of triggering? Optical? Wireless?

The equipment I’ve been using is this:

Eos R camera body

St-e3-rt trigger




What mode do you have the speedlites in?  And where were they set up in relation to the camera?

e.g. if one of the lights' flash is directed even partially to the lens, and you're using ETTL, the pre-flash will be measured which leads to the image being overexposed, so the chosen flash power will be lowered.  For speedlites that are aimed towards the camera like this, you'll need to set the power on that flash manually.


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

The lights were about six feet away from me on either side facing the subjects. I was shooting in manual mode. 

What made me concerned is that the speedlites were flashing and laminating the subject, then, while still flashing when I triggered the shutter, the subject was unlit. It was as though I was shooting without flash at all. 

As far as I know there is no official support for flash on the EOS R. In fact, if you're doing flash photography the R is your worst option of all of Canon's cameras bar none. When I first got mine I had tons of problems with it with every brand of flash out there. I ended up getting a 600EX II but it honestly never really worked right in ETTL mode. I'm of the mind that R camera's don't do ETTL correctly and they are incapable of doing it correctly. This is why Canon didn't want to switch to mirrorless and they only did it because of Sony. By twisting Canon's arm they created this cluster**** and now we're all paying the price. Thanks a lot Sony!

My friend's mom who is a wedding photographer has never had overexposed pictures. When using the original EOS R and using off camera speedlites or on camera flash. And there's support from Canon regarding current product. This sounds like a setting is incorrect or not communicating correctly.


Current Gear: EOS 5D Mark IV, EF F/2.8 Trinity, EF 50mm F/1.8 STM, EF 85mm F/1.8 USM, 470EX-AI & 600EX II-RT

Retired Gear: EOS 40D


Thanks for joining the conversation, Bwalker617!

So that the Community can help you better, we need to know exactly which Canon camera and Speedlite models you're using. That, and any other details you'd like to give will help the Community better understand your issue!

If this is a time-sensitive matter, click HERE search our knowledge base or find additional support options HERE.

Thanks and have a great day!


There are a few multi-multi reply posts on here that talk about the canon radio flashes losing link. I don't know that there has been any definitive solution yet.

click here to view the press release