EOS 90D struggles to focus against bright backgrounds with Sigma lens

[AmateurIrishman]

Hello all. Amateur landscape and wildlife photographer here. Posting this here and a sigma forum looking for answers.

I recently upgraded from a Canon T7 to a used 90D. Not quite ready to drop the money on an RF setup. Fantastic camera, especially paired with my Sigma 17-50 f/2.8. Currently using the sigma 150-600 contemporary for wildlife. Good lens, works well for the most part and I like the extra reach with the crop sensor. However, I am having a very frustrating issue. Not sure if it is an issue with the lens or camera body, both are updated to latest firmware.

When shooting or tracking moving subjects against a bright sky or background, the lens will slowly chatter sometimes all the way down to minimum focus and lock up there. With the lens cap on it seems to behave normally—searching to infinity and back.

I’ve tried C1 set to smooth AF priority, (also did the microadjustments which improved sharpness and overall IQ quite considerably) and playing around with the tracking sensitivity—no improvement. One odd thing I’ve noticed is that when I move the AF points away from the center this problem does not occur, which may be a temporary workaround, but still frustrating.

Any advice would be greatly appreciated. 

[deebatman316]

Is the Sigma standard zoom lens mentioned the Sigma 17-50mm F/2.8 DC OS HSM lens? Is this the lens pictured below.

 

[AmateurIrishman]

Yes. But my apologies, I should’ve stated that it happens mostly with my sigma 150-600. Funny enough, I tried it with my standard just before. Pointed it at the sky- locked up at minimum focus. Moved the af point to the right and it hunted for something to lock on to as expected. Very frustrating when shooting wildlife with the big lens… 

[deebatman316]

I used to own the Sigma 17-50mm F/2.8 DC OS HSM Lens with the EOS 40D. But when I tried using it on the EOS 90D it had focus pulsing issues and had OS issues too. What you have to remember is that particular lens was released when most cameras had 9 AF points. The EOS 90D has the 45 point AF system originally released in 1998 with the EOS-3 film body. It would also be seen in the EOS-1V and later EOS-1D series Digital SLR cameras. Now I’ve never used any of the Sigma 150-600mm lenses. I’ll ping my colleagues who own that lens and camera. To see if there’s any known issues with that setup.

[March411]

Welcome to the community AmateurIrishman.

I owned the 90D for quite some time and several sigma lenses. I did have issues with my lenses racking/hunting as you described for wildlife and when there was a lack of contrast separation. I worked with both Canon and Sigma to resolve the challenges and the recommendation from both groups ensured my firmware was current.

A Sigma dock is required to look at the lenses current configuration so I picked one up. It is a handy little tool and allows you to tweak your lenses as well as complete updates. If you need one and live in the states let me know, I can send you mine and I just gave my last Sigma lens to my daughter.

Several of the lenses required updates and that was resolved as well as updating my 90D. 

Canon also suggested using the 9 point AF selection (or greater), I was using spot and moved to 9 point.  There were also times when skies were high and clear that I used zone.

These adjustments did resolve the majority of the racking/hunting challenges I was having with my 60-600mm and 100-400mm. Now all that being said, my RF lenses do exhibit some of the same challenges under similar conditions. Not nearly as often but there are occasions when it takes a bit of time to grab a lock. Yesterday I was trying to grab a shot of a Hawk with high skies and my RF100-500mm mounted on my R5 was a bit challenged.   

[AmateurIrishman]

Thanks for the info. I do have the dock. I’m actually impressed with how sharp it is now that I did the fine tuning… I also changed C1 to “smooth AF priority”. 

Glad to hear I’m not the only one having this issue. As long as you don’t think anything is seriously wrong with the camera body or lens.

Another thing I might try is setting the focus limiter on C2 to somewheres around 4m, so it doesn’t completely lock up focus at 2.8 like it’s doing now.

one more thing - I saw somewhere that the EOS iTR face priority setting in the camera can make it hard to lock on to certain subjects (I’m having issues with moving subjects, even when not shooting in low contrast situations). I may turn it completely off, wondering if that will help. Would love to hear your opinions on that. 

-JFD  

[March411]

JFD, I do use  focus limiting on my telephoto's and macro lenses with good results. It does reduce travel if the lens is racking. It's good that you have the dock, check the firmware and update it if there is one available. 

Are you using AI servo and back button focus? Have you adjusted the tracking sensitivity? I used -1 and a friend of mine swears by -2, says it's very sticky. 

This video is a bit long and wordy but may be helpful.

[Waddizzle]

Make sure your lens firmware is up to date.  The Sigma OS has always seemed to struggle with Canon AF.

Personally, I disable the Sigma OS. Problems solved. 

[AmateurIrishman]

Yes to both BBF and AI servo. Im hoping to go out and shoot some birds this weekend, so I will play around a bit more with the tracking sensitivity and see what works best. 

Any suggestions for accel/decel tracking and AF point auto switching? Thanks. 

-JFD

[LeeP]

I had a Sigma 17-35 that I loved on my Digital Rebels, but the minute I put it on my R100--with Canon EF/RF adaptor--the lens chattered incessantly. On my R8 it chattered and the vignetting was insane, so the lens went  bye bye that fast and replaced by a Canon 15-30 RF. Problem solved. And yes, I know that is not a response to the poster's question, but just an observation.