topic Re: EF-100-500MM Control Ring not working via EOS R5 in EF & RF Lenses

EF-100-500MM Control Ring not working via EOS R5

JNT — Sat, 01 Aug 2026 16:47:11 GMT

Hello,

I have the R5 with the RF-100-500MM. I cannot get the control ring on the lens to accept a function, ISO. I found the control ring functions in the menu, but it will not assign it. Any help would be greatly appreciated.

Re: EF-100-500MM Control Ring not working via EOS R5

shadowsports — Sat, 01 Aug 2026 20:37:45 GMT

Greetings ,

What shooting mode are you in? Are you using a Custom Fn. mode by any chance or do you have other button customizations currently?

Is this a new lens, used lens. What is its history?

Re: EF-100-500MM Control Ring not working via EOS R5

Waddizzle — Sat, 01 Aug 2026 23:04:16 GMT

What is the factory default control for adjusting ISO? Have you reprogrammed that control for another function? The camera will not accept or allow for two controls controlling exposure settings.

Personally, I would not use a lens control to adjust camera settings. Lens controls should control the lens, not the camera. That’s just my school of thought. For example, what’s going to happen if you use a lens without the control ring?