topic EF-S 17-85mm f/4-5.6 IS USM Focus moves erratically but can't lock in in EF & RF Lenses

EF-S 17-85mm f/4-5.6 IS USM Focus moves erratically but can't lock in

timtom64 — Sat, 13 Jan 2024 16:13:59 GMT

Hello all. Suddenly, whenever put into auto-focus mode, this zoom seems to go a bit crazy as it erratically attempts to focus on something, but it cannot. It just keeps moving erratically but never finds a home. Does anyone have trouble-shooting suggestions? Thank in advance!

Re: 17-85 Zoom Lens Auto-focus issues

Tronhard — Fri, 12 Jan 2024 05:38:47 GMT

Hi and welcome to the forum:
Can you offer some more detail please?
What camera are you using this with?
Has anything at all changed with the camera recently?
What kinds of objects are you attempting to focus on and is that different from previously?
What shooting mode - Av, Tv M etc., are you shooting in?

Re: 17-85 Zoom Lens Auto-focus issues

stevet1 — Fri, 12 Jan 2024 10:07:46 GMT

timtom64,

Does this happen with any other lens, or just this one?

Steve Thomas

Re: EF-S 17-85mm f/4-5.6 IS USM Focus moves erratically but can't lock in

ebiggs1 — Sat, 13 Jan 2024 16:37:05 GMT

More info is probably not needed and about the only troubleshooting thing you can do is a full reset of your camera. Hope it is misbehaving. You can try the lens on a different camera, too. Try other lenses on the offending camera/lens combo.

Remember the lens does not focus. The camera tells the lens when it is in focus. If you don't know how to do the full reset consult your manual. Do that first.

Re: 17-85 Zoom Lens Auto-focus issues

timtom64 — Sat, 13 Jan 2024 16:10:13 GMT

Hi Trevor. Thanks for your reply. I was using it on an 80D, and nothing much has changed. The problem pops up no matter what I try to focus on. And the problem persists no matter what shooting mode I'm in.

Re: 17-85 Zoom Lens Auto-focus issues

timtom64 — Sat, 13 Jan 2024 16:11:01 GMT

Hi Steve. All of my other lenses still work perfectly. Thanks for your reply.

Re: 17-85 Zoom Lens Auto-focus issues

timtom64 — Sat, 13 Jan 2024 16:13:24 GMT

I will try this lens on another body but I'm not optimistic because my other lens work fine on my 80D. I just purchased an R6, and I bought the adapter, so I'll give that a shot pretty soon. I hear you about the lens doesn't focus. I'm thinking maybe it could be dirty contacts? It makes sense for me look into the best way to clean the lens contacts. Thanks for your reply.

Re: EF-S 17-85mm f/4-5.6 IS USM Focus moves erratically but can't lock in

ebiggs1 — Sat, 13 Jan 2024 16:46:37 GMT

"I will try this lens on another body but I'm not optimistic ..."

I hear ya but these things are all you can do to troubleshoot. At least it makes you feel better thinking you did something. I don't know how old your particular lens is but it is a very old design around 20 years or so. You can look for a good used one as they aren't expensive. The EF-S 17–85mm was a step up in IQ along with build quality and focal range compared to the standard kit lens EF-S 18–55mm lens

Re: EF-S 17-85mm f/4-5.6 IS USM Focus moves erratically but can't lock in

timtom64 — Tue, 16 Jan 2024 23:24:23 GMT

OK THIS JUST IN......... I let the camera sit face down without a lens or battery for almost a week, and now it seems to work just fine! Yay! Very stoked. Thanks for your help, everyone. And to anyone else who encounters the same problem, open that camera up and let it sit and dry and know..... THERE IS HOPE!!

Re: EF-S 17-85mm f/4-5.6 IS USM Focus moves erratically but can't lock in

crumhorn — Mon, 25 Aug 2025 15:42:35 GMT

Did you purchase this lens as a refurb or used?

I bought this lens used about a month and a half ago. Verified no damaged by the photos and the seller claimed it was fully functional. When I received it, the lens was a good shape with no issues with the glass. I tested it out very briefly for a couple of days and saw the erratic issue with the AF. Both times I was inside with the first shooting outside the window. But on the third day I took it outside and the AF worked flawlessly every time. I must have focused 300-400 times and every time it worked. And I haven’t had an issue since. I wondered if using it inside the house was the issue with indoor lighting but so far the issue has not returned, even if shooting inside. So, do you have this issue regardless of being inside or out?

Re: EF-S 17-85mm f/4-5.6 IS USM Focus moves erratically but can't lock in

normadel — Wed, 27 Aug 2025 06:29:00 GMT

There are numerous things that can account for trouble autofocusing. Some are:

1. How the focus area is set.If multiple focus points are being used and the field has near and far subjects;

2. If the subject being focused on lacks any texture, contrast or is too dark. There can be big differences between indoor and outdoor scenes in this regard.

3. Your subjects indoors are too close for the lens you are using. All lenses have a minimum focus distance.

Is your indoor lighting bright or dim? This can be widely variable. The camera doesn't know whether it is indoors or outdoors. It knows light brightness and subject focusability.

Re: EF-S 17-85mm f/4-5.6 IS USM Focus moves erratically but can't lock in

timtom64 — Wed, 27 Aug 2025 12:50:10 GMT

The issue persists whether I shoot inside or out. All my other lenses work great. I have since purchased an R6 so I think I'm just going to give up on this lens since I now have another lens that covers the same range. But if anyone pops in with a possible solution, I'm all ears. Thank you, everyone.

Re: EF-S 17-85mm f/4-5.6 IS USM Focus moves erratically but can't lock in

timtom64 — Wed, 27 Aug 2025 12:53:31 GMT

Sorry for the confusion, all. I'm reading through this thread and realize I must have posted a solution to a problem I had with another camera that got wet. Which also means I must not have posted it to the right thread. Uggg.