[DavidSKAF3]

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Is this the autofocus version of this lens? The photo showing the rear has contacts. But it does not say "autofocus" on the barrel like the one in the forum photo.

http://pages.ebay.com/link/?nav=item.view&alt=web&id=331400595623

Sigma 28mm f/1.8 prime lens
Circa 1990's

Thanks,

Dave
http://pages.ebay.com/link/?nav=item.view&alt=web&id=331400595623

[crewl1]

Yes. It looks like it is gone.

[hks_kansei]

I would say that one is autofocus, but I would still check with the seller.

on the bottom left of the mount (near teh bottom most screw) you can see the slotted autofocus connector.

Pentax cameras and lenses of that time period all used a motor in the camera body, with a mechanical connection to the lens.
The contacts are most likely to cater for auto aperture.

[Ole]

Look for either an autofocus drive shaft or two dedicated power contacts located inside the mount (not on the mount itself). Contacts on the mount itself may just mean an "A" lens (auto-aperture, but no autofocus).

[promacjoe]

Look for either an autofocus drive shaft or two dedicated power contacts located inside the mount (not on the mount itself). Contacts on the mount itself may just mean an "A" lens (auto-aperture, but no autofocus).

The 2 contacts inside the camera were not Originally for autofocus. They were for power Zoom. power Zoom did not go over very well, so it was dropped. However for compatibility reasons, The 2 contacts remained in the camera. When the SDM lenses came out, the power contacts were re-used for autofocus.

Note: just because your camera has these two contacts, does not mean that it will work with SDM autofocus lenses. Power is supplied to the autofocus during shutter release. Power for the powers Zoom is supplied by an extra switch. if your camera supports powers Zoom,it will not work with SDM lenses

[DavidSKAF3]

Well I was the high bidder, but I got cold feet near the end and dropped out. I guess whoever won got a great deal on a fast, wide autofocus prime for a mere $132?

Oh well.

Thanks everyone!

[Not a Number]

If you look at the picture of the rear of the lens it has the shaft for the screw-drive at the 7 o'clock position- so it is an autofocus lens

[Just1MoreDave]

Sigma made an AF version of that lens and an MF. Mine says "Sigma MANUAL FOCUS" on it, below the DOF scale.

It's a very sharp lens with OK coatings. The sharpness makes manual focus really easy. Initially I was concerned because the focus ring sweep is quite short. I like the 7 blades. The size is much better than the newer version.