Autofocus defect 4 times - Sigma art lenses on Canon R8

[Leanne16]

Hi,

I'm new here, I registrated so I could ask a question about my Canon R8 and my Sigma lenses. English is not my native language, but I hope you can still follow it.

I've been shooting with the R8 for a few years now. Initially, I used a simple kit lens and the Canon EF 50mm 1.8, both  I still had from my previous Canon (a basic SLR). To use the old lenses, I got a Canon EF-RF mount adapter. This worked fine, but I was lacking some sharpness, so I decided to buy some other lenses. These became the Sigma 50mm 1.4 ART and the Sigma 105mm 1.4 ART. I was very pleased with both, especially the 105mm.

Unfortunately, the 105mm's autofocus suddenly stopped working. I was shooting (indoors, no unusual conditions), but the lens couldn't find focus. It made chattering noises and kept searching for focus. Manual focus worked fine. I tried the lens on other bodies, but the autofocus didn't work there either. It was still under warranty, so I received a different 105mm. After a few months, the same problem reappeared, again "suddenly." The lens couldn't focus again and was making a tremendous amount of noise. Then I had the lens repaired at Sigma (that was in July 2025), and it's been working fine ever since. Sigma told me it was a "coincidence" that I had the exact same problem twice with two lenses.

But it got even weirder. One day, the 50mm lens also started making that noise, searching for focus for a long time. The autofocus continued to work a little, but I sent it in for repair anyway because the noises sounded very strange. I've had the lens back from repair for a month now, and last week the autofocus stopped working completely. It seems the motor is broken now; the autofocus doesn't do anything and doesn't make any noise. Manual focus is still working.

I find it very strange that I've already had this problem with the autofocus on a Sigma lens four times. Could there be a problem with my body, that it's essentially destroying the lenses? Unfortunately, I'm not technically savvy at all. I really enjoy taking great pictures and like it when everything just works, but I know very little about the internals of lenses and cameras.

Does anyone recognize this problem? And what would you recommend? Should I switch to Canon L lenses (I went for Sigma mainly for price reasons and because the sharpness is amazing). Or should I get a different body so I can keep using Sigma? I'm not sure. I do find it very daunting to photograph special moments; I really need more gear to keep on hand, in case the lenses fail.

Thanks for reading!

Sincerely,

Leanne

[shadowsports]

@Leanne16,

I doubt there's anything wrong with your R8 or that it is "destroying" lenses.  Sounds like you've had to run of bad luck. 

It's good that you're using a Canon brand adapter. This is recommended.  

I guess you're buying these lenses used?  Are you buying them from a reputable source or privately?  Do you have a Sigma USB dock, and is the firmware up to date?  

If a lens is completely dead, you probably don't need to spend much time with it troubleshooting. One thing you may want to consider is performing a reset of your camera settings, both main and custom to ensure there isn't a setting that might be affecting your lens performance.  

Canon : Product Manual : EOS R8 : Resetting the Camera https://share.google/Vy5TpcT97PJAoza4A

The process is two-step one for main and one for custom.  This is always recommended when unexpected behavior occurs. It is part of the troubleshooting process.

[deebatman316]

Hi @Leanne16 welcome to the forums. I highly recommend following @shadowsports advice. This sounds like a lens problem since the lens contains the AF motor. Older camera systems housed the AF motor in the camera body. Canon never went this route instead each lens has its own AF motor built in.

[ebiggs1]

"I find it very strange that I've already had this problem with the autofocus on a Sigma lens four times. Could there be a problem with my body,..."

I think this too much of a coincidence. I would look elsewhere.  You didn't offer very much detailed info. Perhaps how you use the lens(s). Your shooting style. How your camera is set. I would do a complete reset.

" the 50mm lens also started making that noise,... I sent it in for repair ... I've had the lens back from repair..."

Wow, I believe you are the only person I have ever heard of that has had a Canon EF 50mm 1.8 repaired.

[Leanne16]

Thanks for your replies!

@ shadowsports, I did indeed buy used lenses , but both from a reputable source; a camera shop. I also had a one-year warranty at both shops. I don't have a Sigma USB dock, so the firmware might not be up to date. Do you think that can cause problems with autofocus like this? 

I followed the steps to reset my camera, thank you. But that is to prevent future problems, you mean? Because it doesn't make a lens any less damaged?

@ebbigs1, Most of the time I'm shooting with kids, outside. The shutter speed varies a lot but is actually always above 1/250, aperture between 1.8 and 5.6. ISO as low as possible, usually between 100 and 800. I always hold the camera with both hands outstretched, the strap around my neck. I don't know what might affect the operation of the lens?

And actually it's not a Canon EF 50mm 1.8 that I had repaired but the Sigma 50 mm 1.4 Art 😉

[March411]

@Leanne16, how's it going? Are you in the states? If not where are you located?

I have a dock I no long use that I could send your way @ no cost if the shipping isn't going to be a challenge.

[LeeP]

I had a 15-30mm Sigma that was 100% a chatterer so I'm not surprised. I too was using it with a Canon-brand EF-to-RF converter. Because it vignetted with my R8, I replaced it with Canon's budget-friendly 15-30mm RF. I have a feeling it's a Sigma issue.

[shadowsports]

Hopefully some of these options / suggestions will work for her.  

I owned many sigma lenses and all worked flawlessly.  I only had one left by the time I went mirrorless, but even it worked well in photo mode.  It was just in cinema OS where it was a few milliseconds slower to focus.  Barely noticeable.  

@Leanne16, you should absolutely verify your Art, Contemporary or Sport lenses are running up to date firmware if you are using on a mirrorless body.  For best possible performance and compatibility

Again however, there was a nothing on the R8 that would "destroy" the AF on a Sigma lens.

Of course it's always possible to get a bad or lower performing copy of any lens, but by in large, every Sigma lens I owned was top notch.  I have absolutely no hesitation recommending them.  Quality, performance and build is all there.  

The sigma USB docks are inexpensive and definitely worth the investment if you have a few of their lenses.  I'd buy or borrow one. @March411 has offered his 🙂

[ebiggs1]

"... it's not a Canon EF 50mm 1.8 that I had repaired but the Sigma 50 mm 1.4 Art"

Well that does make more sense for sure. The FW upgrade is a must. I can also confirm that all my SIgma lenses and that is/was a very large number, have worked very well to exceedly well. In fact two of my most used lenses to this day are Sigma lenses but I am using a 1DX and 1D Mk IV.

Your decision to use more wide open apertures shouldn't effect AF but it could cause OOF images. Don't confuse the two. They are not related.

[ebiggs1]

"I find it very strange that I've already had this problem with the autofocus on a Sigma lens four times."

So do I so, I have to repeat ...........

"I think this too much of a coincidence. I would look elsewhere." Sand, dust, water or saltwater can cause immediate damage and/or lead to fungus resulting in lens damage. The lens(s) may simply be worn out when buying used lenses. Not to mention dropping the lens, etc.