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. 

[March411]

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@AmateurIrishman wrote:

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

-JFD

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Sorry JFD I do not, never used that functionality on my 90D.

Since you have the dock did you hit the Sigma site to see if you had the latest firmware for the 150-600mm. If you are going out this weekend it my be worth doing the update. And I am jealous, I used to hike several times a week and have been hung up for 5 weeks rehabbing a bum hip. If you get some good grabs post some images here so I can live vicariously through you!

And good luck this weekend!  

[AmateurIrishman]

Firmware is updated to version 2.03. As far as I can see from sigma, that is the latest version for this lens. Not sure if there is a way to re-update it, or if that would even help. I’m no geek when it comes to this firmware stuff… 

I think the iTR being set to face priority may have been causing some of my issues with locking on. The YouTube video did mention something about that…

Going to spend a good part of my outing playing around with the tracking settings and try turning the OS completely off for flight shots as someone else mentioned. (I also have the OS customized to dynamic mode on both C1 and C2. Come to think of it this could be a big part of my problem.) Thanks again, I will keep you posted. 

[March411]

JFD, I looked also and the firmware update is fairly recent 8.20.2020, Ver.2.03 Contemporary
150-600mm F5-6.3 DG OS HSM (Canon EF mount).

Was this version loaded on the lens or did you update to this version? If you just loaded it you should see some improvements depending on how old the version was prior, Sigma had several updates for Digital SLR cameras in their firmware bundles and some specific to AF.

[AmateurIrishman]

This is the version already loaded onto the lens…

[AmateurIrishman]

Well anyway I had a little time yesterday to play around with the big lens.

I think the face priority may have been the culprit. I also changed the OS on C1 from dynamic to standard. From what I can see it is locking on to moving subjects a lot better than it was… Remains to be seen. 

[AmateurIrishman]

 

[March411]

Looks pretty clean JFD! The eye and the wing in the foreground look good but I didn't pixel peep 😉

How does the full size image look?