topic Re: EOS R5 + EF-EOS R Adapter: RF lenses work perfectly, but no AF and no shutter with any EF lenses in EOS DSLR & Mirrorless Cameras

EOS R5 + EF-EOS R Adapter: RF lenses work perfectly, but no AF and no shutter with any EF lenses

FlorianM — Thu, 02 Jul 2026 13:19:12 GMT

Hi everyone,

I'm hoping someone has seen this before, because I'm running out of ideas.

My equipment

Canon EOS R5
Firmware: 2.2.1
Canon Mount Adapter EF-EOS R (original Canon, brand new, purchased from Amazon)
Canon RF 14-35mm F4L IS USM
Canon EF 24-105mm F4L IS USM (Mark I)
Canon EF 100mm L (also tested)

The problem

The RF 14-35 works perfectly. I've changed only last week from the 90D to the R5 so I don't have any other RF-lenses.

However, every EF lens I have tested behaves the same way when mounted via the Canon EF-EOS R adapter.

Symptoms:

The camera recognizes that a lens is attached.
Aperture is displayed correctly and can be changed (e.g. f/4 → f/8).
Live View works normally.
The EVF works normally.
Autofocus never starts.
Pressing AF-ON does nothing.
Half-pressing the shutter button does nothing.
Fully pressing the shutter button does not take a picture.
The AF box stays white (occasionally it briefly turned red once, but never focused).

Things I have already checked

Camera firmware updated to 2.2.1
Camera settings reset to factory defaults
Original Canon adapter (not third-party)
Adapter contacts and camera contacts look clean and undamaged
Multiple EF lenses tested (same behaviour)
RF lens works perfectly on the same camera
One Shot and Servo AF both tested
Manual Focus tested (camera still does not release the shutter)
Shutter priority is enabled (not focus priority)
Different batteries tested
Different AF methods tested

Something I noticed

When I mount the RF 14-35 and open the Firmware menu, the camera displays the lens information.

When I mount the EF 24-105 through the adapter, no lens information is displayed in the Firmware menu, even though the aperture is recognized and can be adjusted.

My question

Has anyone ever seen this behaviour?

Is there any setting I may have overlooked, or does this point to a defective Canon EF-EOS R adapter?

Since the RF lens works perfectly, I'm currently wondering whether the adapter could have an electronic fault even though basic communication (aperture control) still works.

Any ideas would be greatly appreciated!

Thanks a lot,
Florian 🙂

Re: EOS R5 + EF-EOS R Adapter: RF lenses work perfectly, but no AF and no shutter with any EF lenses

stevet1 — Thu, 02 Jul 2026 14:53:00 GMT

FlorianM,

You say that the adapter is brand new.

My suggestion is that you look into returning it to Amazon and see if you can get a refund.

I you are able to, then I would purchase an adapter directly through Canon, or a reputalbe Canon reseller like B& H or Adorama.

Steve Thomas

Re: EOS R5 + EF-EOS R Adapter: RF lenses work perfectly, but no AF and no shutter with any EF lenses

SignifDigits — Thu, 02 Jul 2026 20:39:10 GMT

I agree with Steve. Out of curiosity, did you successfully register the adapter on the Canon site? Amazon sales sometimes result in grey market items begin delivered instead of US market products. Usually a grey market item cannot be registered in your account.

Re: EOS R5 + EF-EOS R Adapter: RF lenses work perfectly, but no AF and no shutter with any EF lenses

Waddizzle — Fri, 03 Jul 2026 14:12:34 GMT

“

Something I noticed

When I mount the RF 14-35 and open the Firmware menu, the camera displays the lens information.

When I mount the EF 24-105 through the adapter, no lens information is displayed in the Firmware menu, even though the aperture is recognized and can be adjusted.“

I agree with Steve. Try to get a refund. And do not settle for an exchange. I know Amazon can be very difficult when it comes to getting a refund. They won’t let you cancel an order once you place it. Confirm who the vendor was the you selected and which vendor actually provided it, if you can.

About your comments above, the Canon EF EOS-R accessory is a mount adapter, not a lens adapter. Leave it on the camera. Make sure to turn off the camera when changing lenses. <— This is last is crucial.