topic Re: Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera in EF & RF Lenses

Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera

eapples — Fri, 13 Jun 2025 12:16:53 GMT

Hello: The auto-focus feature will not work when I attach my Canon 18-135 lens to my Canon EOS R camera.

I was using that lens on my Canon Rebel dSLR camera, and it worked perfectly.

My Canon 18-55 and my Tamron 70-300 work fine on the mirrorless camera. I am using an adapter with all the lenses. It's only the 18-135 that won't play nice with the mirrorless camera.

I'm content to use manual focus; but, using the auto-focus feature would make life a bit easier.

If you need more information to help me to resolve this dilemma, I will provide it ASAP. Thank you in advance for your help. AND I apologize if I've already raised this issue in this forum.

Re: Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera

shadowsports — Fri, 13 Jun 2025 13:12:46 GMT

Greetings ,

May we know the brand and type of the adapter that you're using? Only Canon brand adapters are recommended.

Re: Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera

deebatman316 — Fri, 13 Jun 2025 14:01:15 GMT

We also need to know the full and complete name of the lens. There are multiple versions of that lens with the same focal length. Some of which if they can’t communicate with the camera. Then manual focus will not work. This is because the focus ring isn’t directly connected to the lens’ focusing elements. Instead the AF motor is used for manual focus. The focus ring is connected to a digital encoder that tells the camera which way the focus ring is being turned. Then the camera sends power to the AF motor so manual focus works. The STM & Nano USM versions of the lens are focus by wire. So no communication with the camera means you can’t control the lens at all.

Re: Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera

ebiggs1 — Fri, 13 Jun 2025 14:40:54 GMT

My guess is that this is probably the cause ....

"May we know the brand and type of the adapter that you're using?"

... using an off-brand adapter. And i would also guess...

"Some of which if they can’t communicate with the camera."

... is not the case because the lens worked on the Rebel DSLR so it did "communicate". So, that contact has to be in the same position.

Re: Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera

eapples — Fri, 13 Jun 2025 14:53:37 GMT

Canon Control Ring Mount Adapter EF-EOS R

Re: Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera

eapples — Fri, 13 Jun 2025 14:56:58 GMT

Canon EFS 18-135

Re: Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera

deebatman316 — Fri, 13 Jun 2025 15:23:32 GMT

“Canon EF-S 18-135mm” is NOT a COMPLETE name. Canon has made 3 different versions of that and they’re NOT the same lenses. A complete name would be “EF-S 18-135mm F/3.5-5.6 IS STM” lens. The full name can be found on the outer ring after removing the lens cap on all versions of the lens. So please identify which model lens you have.

Re: Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera

eapples — Fri, 13 Jun 2025 15:37:17 GMT

OK, I got it...not a complete name. FYI -- I'm still on the left leg of the learning curve.

Canon Zoom Lens, EF-S 18-135, 1:3.5-5.6 IS USM

Re: Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera

deebatman316 — Fri, 13 Jun 2025 15:49:19 GMT

The lens should work on the mount adapter. But if it’s not communicating at all then the lens won’t work at all. No AF, MF, IS or aperture control. MF won’t work because this lens is what’s called “focus by wire”. When you turn the focus ring and the camera is powered up. The lens sends a signal to the camera which way you’re turning the focus ring. Then the camera sends a signal back to the lens to carry out MF. So with no communication nothing will work. Have you tried a different mount adapter to see if it will work? Also does the camera report an aperture or does it say F/00 or F—. Since it works on a DSLR the contacts on the lens should be fine.

Re: Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera

eapples — Fri, 13 Jun 2025 16:32:50 GMT

Manual focus works, no problem. I get an aperture reading -- currently set at f/8.

I'll continue playing with it. I may be doing something wrong without realizing it. I can live with manually focusing the lens.

Thanks for your help.

Re: Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera

deebatman316 — Fri, 13 Jun 2025 16:46:00 GMT

I would check the AF/MF switch and ensure it’s set to AF instead of MF.

Re: Canon 18-135 Lens, with adapter, Will Not Auto-Focus On My Canon EOS R Camera

eapples — Fri, 13 Jun 2025 17:01:12 GMT

AF is my default setting. I use MF mostly for close-ups.

Thanks again for your help.