Sigma 24-70 F/2.8 DG EX Aspherical Focusing Question

I've acquired one of these rather large, heavy lenses in Nikon mount. But I'm not sure if the manual focusing is working correctly. AF seems fine. However when I switch to manual focus by pulling the focus grip back towards the camera, AF still works and upon turning the focus ring - rather stiffly - the AF drive from the camera is still engaged and can be seen spinning.

Does anyone know if this is normal behaviour for these? I can live with it as I nearly always use AF anyway.

Thanks in advance for any comments.

I suspect it's normal, and you have to use the camera body switch to disengage the 'screwdriver' prong from the lens AF drive. Or maybe there's a clutch internal to the lens that's not being disengaged by the sliding focus barrel?

Dunno really, but I bought one of those Sigmas along with a Canon 5D (Mk1) shortly after the camera was introduced. I was well impressed by the camera, but that sample of Sigma lens made it look worse than the 6 Mp Minolta Dimage that was my first venture into digital photography. A Tamron SP 28-75 f/2.8 quickly replaced the Sigma and was a several fold improvement.

use the camera body switch to disengage the 'screwdriver' prong from the lens AF drive.

D'oh! Thanks Joe, correct, how did I miss that? As to quality, I haven't taken any pictures yet, it only came yesterday.

There is another issue with focusing, the action stiffens at short distances, less than 2 feet or so, and It wont AF back out again. Just switch to manual to free it up. And plenty of zooms don't focus that close anyway.

Whatever comes out of it, I only paid £59 plus postage, so I won't be too disappointed. Now to find an 82mm filter ...

There is another issue with focusing, the action stiffens at short distances, less than 2 feet or so, and It wont AF back out again.

That doesn't sound good. It might just be dried grease at that end of the helicoid if the lens was habitually used at long distances. Or it could be a sign of the lens being dropped on its nose.

I once let a Tokina 28-70 zoom slip off the back seat of my car - a drop of about 18" at most onto a carpeted car floor. The rider bushes in the zoom mechanism got cracked and the zoom action stiffened to unusable at about 35mm. I did manage to ease it after dismantling, but that lens was never the same again. No great loss, since it was pretty soft to begin with, and that was on film. But I still can't bring myself to bin that piece of junk.

Or it could be a sign of the lens being dropped on its nose.

I would be more concerned if the sticking was at long distances.

Thanks Hans that's understood. Here's a shot from it:

Looks pretty good John. Congratulations, I think you struck lucky and got a good sample!

Also looks like a (non-gastro) decent pub, and those are getting pretty rare too.

Ah, maybe not. The first item on its website is - "Book a table". What happened to "Walk up to the bar and buy a well-kept, hand-pulled real ale"?