topic Re: Canon RF 100-400 Autofocus problem in EF & RF Lenses

Canon RF 100-400 Autofocus problem

Len29 — Mon, 27 Feb 2023 21:01:11 GMT

Hello,

Does anybody have an issue with autofocusing in 400mm with this lens? When I extend the lens to 400mm and try to focus, the lens is not focusing. I have to retract the lens to 100mm and refocus. Only then autofocus works. It happens almost every time in any mode(M,Av,Tv or Fv). Camera Canon R6.

Re: Canon RF 100-400 Autofocus problem

rs-eos — Mon, 27 Feb 2023 21:26:01 GMT

I don't own this lens, but just a couple questions to help troubleshoot:

If you adjust the zoom just a bit less than 400mm, does it then work? i.e. does it fail only when exactly at 400mm?
Any differences if the stabilizer is on vs off?

Re: Canon RF 100-400 Autofocus problem

Len29 — Mon, 27 Feb 2023 21:38:23 GMT

This is my second RF100-400 IS USM lens. Both behave the same, whether IS is ON or OFF. The autofocus is not working when I extend the lens to 400mm and it's out of focus no matter which button I use(back buttons or main release button). I tried to gradually zoom out while holding AF button and sometimes it start focusing at around 135mm. But most of the time I have to retract the lens to 100mm in order for lens to start autofocusing.

Re: Canon RF 100-400 Autofocus problem

deebatman316 — Mon, 27 Feb 2023 21:48:49 GMT

If you have other RF Mount lenses do they work correctly on this camera.

-Demetrius

Current Gear: EOS 5D Mark IV, EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 50 F/1.8 STM, EF 85mm F/1.8 USM, EF 70-200mm F/2.8L IS III USM, 470EX-AI & 600EX II-RT

Retired Gear: EOS 40D & Sigma 17-50mm F/2.8 EX DC OS HSM

Re: Canon RF 100-400 Autofocus problem

Len29 — Mon, 27 Feb 2023 21:57:42 GMT

Update: The "problem" is solved. In the menu; AF; #4; "Lens drive when AF impossible" was OFF. When I changed it to ON, AF is working without any problem.

Re: Canon RF 100-400 Autofocus problem

rs-eos — Mon, 27 Feb 2023 23:24:25 GMT

You shouldn't have to enable that setting to force the lens to focus.

This is sounding like you have an issue with the camera. I would first reset all settings and try things out again. If the issue remains, you probably should look at sending it in for a repair.

Re: Canon RF 100-400 Autofocus problem

Len29 — Tue, 28 Feb 2023 00:03:34 GMT

Thanks, You may be right. My other RF24-105 L f/4 lens is not doing this. But it's not 100-400mm zoom. I'm going to call Canon tech support tomorrow about this, will see what they say.

Re: Canon RF 100-400 Autofocus problem

shadowsports — Tue, 28 Feb 2023 00:11:00 GMT

@Len29,

I think the default is "on" for this setting. I'd have to verify.

Canon : Product Manual : EOS R6 : Customizing AF Functions (start.canon)

Re: Canon RF 100-400 Autofocus problem

Len29 — Tue, 28 Feb 2023 00:49:18 GMT

I just reset the camera setting and the default is "on" for this setting.

from the canon r6 manual below instructions need to be expended:

Re: Canon RF 100-400 Autofocus problem

Len29 — Tue, 28 Feb 2023 21:23:50 GMT

I called Canon tech support today regarding my issue. Their response was: Your lens and camera work within the normal operation. And they suggest using "Lens drive when AF impossible" and "Continue focus search: ON.

Re: Canon RF 100-400 Autofocus problem

jrhoffman75 — Tue, 28 Feb 2023 23:17:19 GMT

@rs-eos wrote:
You shouldn't have to enable that setting to force the lens to focus.
This is sounding like you have an issue with the camera. I would first reset all settings and try things out again. If the issue remains, you probably should look at sending it in for a repair.

That is exactly what the problem is. Long telephoto lens can get grossly out of focus so the camera can't "see" anything to start focusing on. I had the exact same problem with my 1D X MkIII. I had utilized some recommended settings from an online user. Lens wouldn't focus when I was trying to focus on ospreys flying. If I manually focused to get the birds close then it focused OK.

If I switched out of the custom settings back to my basic it worked fine. Took a while to sort out the problem.

Re: Canon RF 100-400 Autofocus problem

rs-eos — Tue, 28 Feb 2023 23:31:30 GMT

Thank you for this added explanation, John! I had assumed incorrectly about the default value of that setting as well.

Re: Canon RF 100-400 Autofocus problem

wgeoghegan — Fri, 09 Jun 2023 20:34:40 GMT

I had no idea that happened while I was taking pictures. Lost lots of shots. I thought the lens was bad.

There are so many choices on the R6 that just understanding what each one means is a struggle. I wish the manual were set up differently so for example if one looked up autofocus everything would be on one or a few pages. As it is currently 19 different pages come up on a search of the manual for autofocus.

Re: Canon RF 100-400 Autofocus problem

wgeoghegan — Fri, 09 Jun 2023 20:37:00 GMT

So, yes I was using the RF 100-400 lens with my R6 and my shots were blurred at 400 mm. My shots at 100 mm were fine.

Re: Canon RF 100-400 Autofocus problem

ebiggs1 — Mon, 24 Nov 2025 16:48:31 GMT

You know this thread is almost 3 years old? Probably no one around any longer.

Re: Canon RF 100-400 Autofocus problem

rgl47 — Mon, 24 Nov 2025 19:25:38 GMT

Answer to your first question is yes. Response to your statement is no, I didn't know no one was around any longer. I was trying to reach or elicit information directly from Ricky, aka rs-eos. Thank you.