EOS R6, EF 100-400mm f/4.5-5.6L IS II USM: Extender EF 1.4X III Switches To Manual Focus

[wushuyvr]

Hi everyone,

I’m having an issue with my Canon R6. I’m using it with an RF to EF Adapter, a 1.4 Extender iii, and an EF100-400 mk ii lens. When I first turn the camera on, everything works perfectly, and it focuses as it should. However, after a few shots, it suddenly switches to manual focus (MF) on its own.

Has anyone else encountered this problem? Any ideas on why it’s happening or, better yet, how to fix it? I’d appreciate any insights!

[deebatman316]

Does the lens work correctly with the teleconverter removed. Also if you have a DSLR will it work correctly on there. Does the camera still report aperture when this happens or does it report F/00 or F--.

[wushuyvr]

Hi deebatman316,

when I take off the extender, the ef100-400 mk ii works and focuses as it should. That’s why I’m thinking the issue is with the extender.

[deebatman316]

Does it work on a DSLR camera properly. To remove the adapter from the picture.

[p4pictures]

If you can, then try swapping the mount adapter out for another one. I have seen odd issues with a Canon mount adapter in the past myself. 

[ebiggs1]

"I’m using it with an RF to EF Adapter, a 1.4 Extender iii, ..."

Both are Canon brand accessories? If not that is your problem.