topic Re: EOS R5 Mark II + RF 600mm F4 L IS USM switching to manual focus in EOS DSLR & Mirrorless Cameras

EOS R5 Mark II + RF 600mm F4 L IS USM switching to manual focus

Smews — Mon, 15 Dec 2025 13:43:12 GMT

I have started having issues using my Canon R5 Mark ii with the RF 600mm F4 L IS USM lens. Occasionally, it switches to manual focus mode, by itself. I.E. I do not change the lens switch or any other setting, but auto-focus stops working and the viewfinder shows manual focusing aids. Turning the camera off and on does not fix it. However, turning the focus ring does! (I don't remember changing any settings that might cause this and I do not remember it happening before the last week.) Any ideas what could be the problem, before I send them to Canon to be fixed, only to be told it is a user error?

Re: Canon R5 Mark ii + RF 600mm F4 L IS USM switching to manual focus

Waddizzle — Sat, 13 Dec 2025 18:48:01 GMT

Your lens is capable of entering a “manual override” focus mode. That’s all I know.

Re: Canon R5 Mark ii + RF 600mm F4 L IS USM switching to manual focus

Anonymous — Sun, 14 Dec 2025 10:04:16 GMT

Maybe the camera looses (partial)contact with the lens, try cleaning the contacts. See if the metal rings on camera/lens are still firmly attached.

Re: Canon R5 Mark ii + RF 600mm F4 L IS USM switching to manual focus

Waddizzle — Sun, 14 Dec 2025 13:31:43 GMT

“ Maybe the camera looses (partial)contact with the lens, try cleaning the contacts. See if the metal rings on camera/lens are still firmly attached. “

Unless you can see debris on the contacts, cleaning them rarely works. In fact, you are likely to damage the gold plating if you are not careful.

The lens has a switch that can disable AF temporarily, putting it into a manual focus mode.’

Re: Canon R5 Mark ii + RF 600mm F4 L IS USM switching to manual focus

Anonymous — Sun, 14 Dec 2025 13:48:37 GMT

'The lens has a switch that can disable AF temporarily, putting it into a manual focus mode.’

But the OP says: ' I do not change the lens switch or any other setting' although it could be a defect in the switch. These switches are very hard to accidentally move. With heavy lenses there's more change of a bit of play/bad contacts.

Re: Canon R5 Mark ii + RF 600mm F4 L IS USM switching to manual focus

Anonymous — Sun, 14 Dec 2025 13:55:04 GMT

Or or you talking about these buttons? This works only as long as you press the button. I own the RF400 2.8, functionally the same lens(they even share the manual) and I've never managed to accidentally press one, they are to far forward(or my arms are too short😄).

Re: Canon R5 Mark ii + RF 600mm F4 L IS USM switching to manual focus

Waddizzle — Sun, 14 Dec 2025 14:11:54 GMT

Yes. The “AF Stop” button(s).

Re: Canon R5 Mark ii + RF 600mm F4 L IS USM switching to manual focus

Smews — Sun, 14 Dec 2025 15:19:22 GMT

Those buttons are far to distant to accidentally press 😀

Also, the AF/MF switch is not easy to move accidentally, either.

I will check the contacts for anything obvious, but I have switched in/out my RF 1.4x TC a few times, so my guess is that should have resolved a contact issue.

I think the biggest clue is that it is fixed by manually altering focus. But I have no idea what that could mean.

I have plans for the next few weeks, so I will live with it and hope it does not get worse and, if it does not miraculously fix itself, it looks like it will all be on the way to Canon in the New Year to take a look!

Thanks for the suggestions.

Re: Canon R5 Mark ii + RF 600mm F4 L IS USM switching to manual focus

Anonymous — Sun, 14 Dec 2025 18:42:44 GMT

Those buttons are far to distant to accidentally press

Also, the AF/MF switch is not easy to move accidentally, either.

I agree, my answer was to Waddizzle.

I think the biggest clue is that it is fixed by manually altering focus. But I have no idea what that could mean.

That partly why I was thinking play/loose contact, as soon as you grab/move the focussing ring you're altering pressure on the lens and contacts.

Re: Canon R5 Mark ii + RF 600mm F4 L IS USM switching to manual focus

Smews — Sun, 14 Dec 2025 19:10:06 GMT

Hmm. Next time it happens, I'll try to remember to just try moving the camera/lens join and see if that works. Would confirm the hypothesis and the need to go back to Canon to be fixed.

Re: Canon R5 Mark ii + RF 600mm F4 L IS USM switching to manual focus

Waddizzle — Sun, 14 Dec 2025 21:49:49 GMT

“ I will check the contacts for anything obvious, but I have switched in/out my RF 1.4x TC a few times, so my guess is that should have resolved a contact issue. “

A teleconverter? That’s new.

Does the issue appear with or without the TC installed? Let’s test and use the lens without it. Maybe you have a faulty TC.

Re: Canon R5 Mark ii + RF 600mm F4 L IS USM switching to manual focus

Smews — Mon, 15 Dec 2025 06:46:09 GMT

Sorry I did not mention it originally, but it happens both with and without the TC, so did not think it important. Of course it would probably be cheaper to fix if it was the TC 😀

I will be doing some testing to see if there is any pattern, etc.

Re: EOS R5 Mark II + RF 600mm F4 L IS USM switching to manual focus

Smews — Wed, 11 Feb 2026 17:49:22 GMT

I thought I would follow-up in case anyone else has the same problem.

I found time to send the complete setup to my Canon Service Centre and it is now fixed. Actually, there was nothing wrong with it 😀. The other thing I neglected to mention was that the lens has a Lens Coat camo-cover on it. It appears that the covers over the focus ring and the focus preset ring had moved, such that moving the focus ring also moved the preset ring and held it in position. Apparently doing that switched to manual focus mode and caused the problems I had been seeing. (Hence turning the focus ring the opposite direction freed up the preset ring, enabling auto-focus again.)

Simple fixes are rearranging the ring covers or turning the preset function off.

All a bit embarrassing, but glad it was nothing serious wrong.