If you read my previous post about the back focus problems I experienced with my new Sigma 24-70mm lens, you will know that I ended up sending it back to Sigma for a recalibration. I also didn’t send it back with my camera as requested.

The lens was with Sigma slightly longer than I expected but as I was mostly under lockdown, I wasn’t in a massive rush to get it back. As long as when it was returned it worked as expected I would be happy. The last time I sent a lens in for a service it was back with me in just under a week. This time it took just under three weeks.

Those of you who pay attention will know that means that I’ve had the lens back for a few weeks now. I admit that I’m a little late writing this update. Life has gotten busy recently, for one reason or another, which I won’t bore you with.

As soon as I received the lens back from Sigma, I unpacked it and checked out the service report they include with any lens you return for service or repair. The report indicated that they had replaced the MF sensor, whatever that is. They had then recalibrated and checked the lens before returning it to me. A quick google returned nothing obvious for the MF sensor but I’m assuming it has something to do with the manual focus mechanism.

I eagerly attached the lens to my D850 and checked out the auto focus to see if the focus hunting issue when fully zoomed in at 70mm had been resolved. Initial tests were good, no hunting, but as I moved the camera around with the camera set in AF-C mode, I was quickly disappointed. The camera started focus hunting again when zoomed in at 70mm and the focus distance was close to the camera.

I decided to break out the tripod and do a quick auto focus fine tuning. It was at that point I remembered something important. Before sending the lens back to Sigma I’d already done some auto focus tuning with the lens on my D850. As part of that process I made a manual adjustment of -10 to be able to complete the fine tuning using the Sigma USB dock. My camera had remembered this adjustment.

I erased the stored adjustment for the Sigma 24-70mm and re-tested the lens. To my relief, the issue was resolved. No more focus hunting and the focus looked a lot more accurate than it did before servicing. I did a quick automatic focus adjustment using the built-in feature of the D850 and that also worked and returned a value of -4. Not a massive adjustment and it did improve the focus accuracy at 70mm.

I am planning to do a full calibration on the lens now I’m happy it’s working as designed. I just need to find a few hours to do it. Overall, I’m happy with the Sigma 24-70mm now and hopefully I can get out and get some good shots with it. Once again, excellent service from Sigma UK which will definitely influence my future purchasing.

There are bad copies of lenses out there from all manufacturers, it’s just nice to know that if I do need to send a Sigma lens back, they don’t need my camera body to go with it. I don’t doubt that if I had returned my camera body with the lens, the focusing would be spot on and I wouldn’t need to take the time to fine tune it. I just don’t feel comfortable trusting any courier with £3500 worth of gear.

Thanks for stopping by and taking the time to read this post. If you have any comments, feel free to drop me a line below.

Have a good one.