topic Re: Canon 100-400 EF 4.5/5.6 not focusing (auto or manual) in EF & RF Lenses

Canon 100-400 EF 4.5/5.6 not focusing (auto or manual)

SethHarrison — Mon, 29 Aug 2022 19:20:15 GMT

I had to tighten a screw on the lens mount of my 100-400 lens because it was loose and not coupling completely with the camera. After tightening it (and now getting a good fit with the camera), the lens is not focusing, either in autofocus or manual focus) In autofocus, I can hear the motor working when I depress the shutter halfway, but it doesn't focus, and as I said, it also does not focus in manual focus mode. This is happening on two different 1Dx bodies, so I know it's not the camera. Any ideas?

Re: Canon 100-400 EF 4.5/5.6 not focusing (auto or manual)

Tronhard — Mon, 29 Aug 2022 19:38:30 GMT

My first thought is to slightly back off the tight fit you got and see if that makes a difference.

Re: Canon 100-400 EF 4.5/5.6 not focusing (auto or manual)

SethHarrison — Mon, 29 Aug 2022 19:39:49 GMT

I was thinking the same thing. I'll try that. Thanks!

Re: Canon 100-400 EF 4.5/5.6 not focusing (auto or manual)

ebiggs1 — Sun, 04 Sep 2022 16:24:28 GMT

"I had to tighten a screw on the lens mount of my 100-400 lens because it was loose and not coupling completely with the camera."

I think unrelated and just coincidence. It needs service. Call Canon 1 (800) 652-2666

Re: Canon 100-400 EF 4.5/5.6 not focusing (auto or manual)

jrhoffman75 — Sun, 04 Sep 2022 19:13:35 GMT

@SethHarrison wrote:
I had to tighten a screw on the lens mount of my 100-400 lens because it was loose and not coupling completely with the camera. After tightening it (and now getting a good fit with the camera), the lens is not focusing, either in autofocus or manual focus) In autofocus, I can hear the motor working when I depress the shutter halfway, but it doesn't focus, and as I said, it also does not focus in manual focus mode. This is happening on two different 1Dx bodies, so I know it's not the camera. Any ideas?

When you say “not coupling” do you mean the loose screw prevented full rotation of the lens so it wouldn’t click into position?

Re: Canon 100-400 EF 4.5/5.6 not focusing (auto or manual)

Tronhard — Sun, 04 Sep 2022 19:16:59 GMT

You may be right Ernie, but getting the OP to simply take some of the pressure off the lens screw might be a resolution that will be a lot cheaper and more convenient that sending it in for Canon to do the same and charge for it. If that doesn't work, then absolutely invest in a service.

Re: Canon 100-400 EF 4.5/5.6 not focusing (auto or manual)

jrhoffman75 — Sun, 04 Sep 2022 19:30:45 GMT

Hi guys.

If that works Trevor it would still recommend the OP send it in for service. The lens mount is a rigid piece. It is held in by four screws. If everything is to factory spec completely removing one screw shouldn’t make a difference (I just tried this on an old lens that I have on my display shelf).

Re: Canon 100-400 EF 4.5/5.6 not focusing (auto or manual)

ebiggs1 — Mon, 05 Sep 2022 16:16:20 GMT

"If everything is to factory spec completely removing one screw shouldn’t make a difference..."

Of course but if it makes him feel like he did something go for it. Than send it to Canon!

Re: Canon 100-400 EF 4.5/5.6 not focusing (auto or manual)

SethHarrison — Mon, 05 Sep 2022 21:40:18 GMT

Thanks all, CPS has the lens and is taking a look at it.