topic Re: EF 70-200mm f/2.8L IS III USM constant focus noise in EF & RF Lenses

EF 70-200mm f/2.8L IS III USM constant focus noise

PhotoDad — Sun, 22 Feb 2026 04:48:29 GMT

My r6ii with rf-ef adapter and 70-200 f2.8 iii lens is now making a constant noise that sounds like it's struggling to find the focus. I've never heard it before. I have bbf set. Even with lens set to manual focus, the focus motor seems to be running.

Re: EF 70-200mm f/2.8L IS III USM constant focus noise

PhotoDad — Sun, 22 Feb 2026 04:48:50 GMT

Sorry... Posting from my phone which was glitchy and accepted the post before I was finished.

I tried a second lens .. Worked great. It's the lens itself and not the camera body. Any thoughts as to why it's continuously trying to focus? I tried it on an old rebel xti. Same issue but to a lesser degree.

Re: EF 70-200mm f/2.8L IS III USM constant focus noise

SignifDigits — Sun, 22 Feb 2026 12:47:41 GMT

Does it still make the noise with the Stabilizer off? Could just be the normal sounds of stabilization that you're just now noticing. If it's still making the noise with the Stabilizer switched off what are all 4 switches on your lens set to? With AF switched on the lens off the only thing that should be making a noise is stabilization, I think/hope, and with that off electronic sounds should stop. If not, then we can go through the "More camera shooting settings - Servo, One-Shot or Auto?, Make sure your connectors are all clean and making contact, etc." kind of thing, but I suspect you might want to call Canon directly at that point.

Re: EF 70-200mm f/2.8L IS III USM constant focus noise

shadowsports — Sun, 22 Feb 2026 13:37:05 GMT

Greetings,

Check and see if you have Preview AF, formally Continuous AF enabled. The setting would cause the camera to focus continuously without any user action. It could also be related to IS as my colleague pointed out. 🤔

https://cam.start.canon/en/C012/manual/html/UG-05_AF-Drive_0070.html

Re: EF 70-200mm f/2.8L IS III USM constant focus noise

ebiggs1 — Sun, 22 Feb 2026 15:40:18 GMT

"Make sure your connectors are all clean and making contact, etc."

Avoid that advice. It rarely to never, way mostly never, is the problem and if done incorrectly can cause irreparable damage to the contacts. The act of mounting and removing lenses is generally all that is needed to keep the contacts in good nick. There is a super thin gold plating on them that can be damaged if cleaned too often or incorrectly.

However, if you must get a qtip with a small amount of denatured alcohol and rub the contacts gently. Do not use a pencil eraser, never ever, as some folks suggest as it will certainly damage the contacts.

Re: EF 70-200mm f/2.8L IS III USM constant focus noise

SignifDigits — Sun, 22 Feb 2026 16:54:15 GMT

It was not advice, but was mentioned, in my mind, as one of the always-asked-and-mentioned questions/suggestions that usually follow. If he has a noise in the lens with the AF switch off and Stabilizer off IMO the appropriate next step is a call to Canon. I have read your reply enough times to know to never suggest it 🙂 Rick since you mentioned those would those camera setting override the AF off button and still cause the AF motors to engage? I had thought not, but as you know I'm still a rookie here.

Re: EF 70-200mm f/2.8L IS III USM constant focus noise

shadowsports — Sun, 22 Feb 2026 17:27:55 GMT

If you configure BBF and don't change the shutter to metering only the camera will continue to focus if you have Preview AF or Continuous AF enabled. I just threw it out there as possibility. Sometimes people mistake IS noise for the focus motor as you mentioned. Some lenses make more noise than others. 😃

Its under C.Fn 3 shutter button in half press. Change from metering AF start to metering only.

https://cam.start.canon/en/C012/manual/html/UG-09_Custom_0030.html#Custom_0030_3-4

I don't use BBF myself but I do use the AF on button to wake a camera frequently.

Re: EF 70-200mm f/2.8L IS III USM constant focus noise

deebatman316 — Sun, 22 Feb 2026 17:12:32 GMT

@SignifDigits When EF/EF-S lenses are adapted on EOS R Series with Continuous AF/ Preview AF ENABLED the camera will constantly drive the AF motor and IS (if the lens is equipped with it). This also prevents lenses with mechanical focus override from focus being overridden. Since the camera is constantly driving the AF motor. The lens has a clutch to prevent damage to the lens. When trying to turn the focus ring with the camera driving the AF motor you'll feel internal pushback from the lens. This is the lens' clutch protecting the AF motor from damage.

@SignifDigits wrote:

It was not advice, but was mentioned, in my mind, as one of the always-asked-and-mentioned questions/suggestions that usually follow. If he has a noise in the lens with the AF switch off and Stabilizer off IMO the appropriate next step is a call to Canon. I have read your reply enough times to know to never suggest it 🙂 @shadowsports since you mentioned those would those camera setting override the AF off button and still cause the AF motors to engage? I had thought not, but as you know I'm still a rookie here.

@SignifDigits Yes it will. AF Stop functions differently in EOS R Series cameras vs DSLRs. Since the only time focusing happens in DSLRs is when the AF Start button is used. But on mirrorless the AF motor is always active. Continuous AF/ Preview AF should be DISABLED. Its not only a drain on the battery but you cannot override focus on older EF/ EF-S with mechanical focus override. Focus By Wire EF lenses only allow focus override in One Shot AF. This limitation dates back to the first Focus By Wire lens in 1987 (EF 300mm F/2.8L USM) lens.

Re: EF 70-200mm f/2.8L IS III USM constant focus noise

shadowsports — Sun, 22 Feb 2026 17:31:34 GMT

Expert reply @deebatman316 《《《《《

Re: EF 70-200mm f/2.8L IS III USM constant focus noise

deebatman316 — Sun, 22 Feb 2026 17:38:59 GMT

Thanks @shadowsports 😊👍

Re: EF 70-200mm f/2.8L IS III USM constant focus noise

SignifDigits — Sun, 22 Feb 2026 17:51:37 GMT

Thanks Demetrius! I thought I had read in your KB that turning the autofocus switch "Off" on the lens overrode the camera AF settings. I guess I misread and/or misunderstood. Thanks for setting me straight. I find it bizarre behavior but nobody ever asked me to design a camera 🙂

Re: EF 70-200mm f/2.8L IS III USM constant focus noise

deebatman316 — Sun, 22 Feb 2026 18:52:28 GMT

@SignifDigits wrote:

Thanks @deebatman316 ! I thought I had read in your KB that turning the autofocus switch "Off" on the lens overrode the camera AF settings. I guess I misread and/or misunderstood. Thanks for setting me straight. I find it bizarre behavior but nobody ever asked me to design a camera 🙂

@SignifDigits setting the lens AF/MF does override the camera focus setting. The specific camera setting called Preview AF/ Continuous AF causes the lens to focus constantly. Even if the AF Start button isn't being pressed. This will also cause IS to be on constantly too so its recommended to set it to DISABLE. Older lenses were not designed for the AF & IS to be active all the time.

Re: EF 70-200mm f/2.8L IS III USM constant focus noise

PhotoDad — Sun, 22 Feb 2026 23:01:17 GMT

Many thanks to all of these suggestions. The fact that it happened when I've had the lens for 2 years and the camera for 1 and don't typically change the preview af/continuous AF option AND that it occurred on the xti I pulled out of the closet made me think this was a lens issue. I ran through your suggestions and found that I had preview AF disabled; I had Lens drive when AF impossible enabled (but no change when I disabled it); turning off image stabilization on the lens solved the problem. So this raises the next question: if it has never generated this noise before (I've never not shot without IS) is it time to get it serviced? It sounds almost like the motors are ginding a bit as I feel the body vibrating.