Auto Focus Problem with EF 100-400mm f/4.5-5.6L IS II USM with EF-EOS R Adapter

[CTJohn]

I just returned from a two week African safari and loved the EOS R performance. One issue I had repeatedly was an inability for the camera to focus my EF 100-400II lens once the camera had shut down to save the battery. I would half depress the shutter button to bring the camera to life, but often needed to manually focus the lens near proper focus before auto focus would kick in. I called Canon, and they set up an EOS R with the EF 100-400 lens and they had the same issues in the lab. They said they'll report the issue up the line, but didn't give me resolution. Has anyone else had this issue?

 

[Jonathan Thill]

Saw the same thing with the 100-400MKI on my R, I turned off the power saving and just manually turn the camera on and off now and have not had the issue since.

Not really a fix but works for me

 

[JohnyT]

I saw a similar condition upon trying various EF lenses on my newly acquired EOS R, my 100-400 would not focus. I fussed around a bit and finally cleaned the contacts on the EF 100-400, and voila it works! Happy with the EOS R I like the physical size and fast focus!