Sigma 70-200 2.8 OS AF on 7D

I recently purchased a Sigma 70-200 2.8 OS from another member here and in my initial tests, the AF seemed to hesitate before locking focus.

For example, on one shot AF with the center zone selected and trying to focus on a squirrel, it focused correctly for a fraction of a second, then kept on cycling from the correct focus to a point beyond the squirrel and back, a few times a second. Also, the squirrel just about filled the center AF zone, so it wasn't too small to pick up.

This wasn't the only time it did it, it also did it on many other subjects. Sometimes it would lock focus, but sometimes I would have to manual focus it because it wasn't locking.

Any ideas? I still need to throw it on my XSi and test it out there to see if it still does it.

Thanks for your help!

This is abnormal and should not happen, especially if you've experienced this under various circumstances. Test it on your XSi and if it's the same, it should be returned or sent in for service.
My copy's AF is snappy and accurate on all 3 of my bodies, even with TCs attached.

Okay, I will do some further testing tonight when I get home and go from there. I'd hate to have to return it, but I guess if it isn't working correctly for me, I don't want to spend a lot more money getting it repaired or adjusted.. Any idea how much it would be?

If the lens was purchased from an authorized Sigma dealer by the previous owner then more than likely you can have it repaired under warranty. You only pay shipping to the Sigma facility.

I didn't receive any original purchase information with it. It does have a Mack warranty, but the seller said that would probably do no good because they didn't have the receipts from the sale. I guess I need to give both Sigma and Mack a call tonight to see if they can do anything for me?

viper42391 wrote in post #13975988
I didn't receive any original purchase information with it. It does have a Mack warranty, but the seller said that would probably do no good because they didn't have the receipts from the sale. I guess I need to give both Sigma and Mack a call tonight to see if they can do anything for me?

Yes, I'd do that.

viper42391 wrote in post #13975988
I didn't receive any original purchase information with it. It does have a Mack warranty, but the seller said that would probably do no good because they didn't have the receipts from the sale. I guess I need to give both Sigma and Mack a call tonight to see if they can do anything for me?

Call sigma and they'll tell you its only good for the ORIGINAL owner. It will transfer with receipt if its a gift--it won't fly if you bought it from someone else.

The mack warranty, if good, will be sufficient. It costs $20 to transfer the warranty title over to a new owner, which you can do on your own.

MOkoFOko wrote in post #13976268
Call sigma and they'll tell you its only good for the ORIGINAL owner. It will transfer with receipt if its a gift--it won't fly if you bought it from someone else.

The mack warranty, if good, will be sufficient. It costs $20 to transfer the warranty title over to a new owner, which you can do on your own.

Okay, do you know if Mack will require the original receipt?

Have the lens checked out by Sigma if you can't exchange or return it especially if it doesn't behave on your other body - mine doesn't have any wierd hunting behaviour on either my 7D or 350XT.

I just checked it on both bodies tonight... The only time it hunted (after taking it off and putting it back on to the 7D) was focusing on a glass soda bottle, so I'll give it that. Other than that, I put it on Servo and moved around the house and it locked on to everything pretty quickly.

I'm thinking now that I got it, put it on the camera and didn't take it off until tonight. There may have been a faulty connection between the camera and lens.

On the XSi, the focusing was a tiny bit slower, but it locked there too.

I need to go out and get another real-world test here soon to make sure it wasn't just making me hopeful However, it was pretty dark in my house, so I would think if it were going to hunt, it would have been then.

I will keep you posted on the progress!

Thanks for your help!

I think you should have started with mentioning the clear soda bottle in the first post
That is a confusing AF target with some of the light reflecting and some of the light from objects behind coming through the bottle. No wonder it hunted.
Yeah, go out take a few real world shots (preferably not soda bottles ) and go from there.

I wasn't originally trying to focus on the bottle.. That was the only thing that it hunted on in my test in my house tonight. Before, it was hunting on a stationary squirrel and a building... Less transparent things

Sorry to resurrect an old thread, but I just called Mack yesterday to see what they can do for me.. The original owner had not registered the warranty yet, so I didn't have to pay a transfer fee (win), and they said the original receipt is not required, only a copy of the mack warranty card.

So after the upcoming airshow festivities the next few weekends, I think i will be sending it away to hopefully be adjusted.

It is weird... It seems like it hunts more in the daylight then in darker conditions. When I tested it in my house, it did fairly well, but outside in the daytime, it will sit there and hunt, sometimes never locking focus.

viper42391 wrote in post #14138057
It is weird... It seems like it hunts more in the daylight then in darker conditions. When I tested it in my house, it did fairly well, but outside in the daytime, it will sit there and hunt, sometimes never locking focus.

Some lenses (this one no doubt) support multiple AF motor speeds and would be utilised based on light levels. The faster AF speed probably jumps past the subject back and forth but the slower speed (in low light) might be fine.

Either way, good to hear that you'll be getting it fixed!