One caveat: if it doesn't have an in-lens motor, you'll have problems using it with the Nikon D40...

Thanks for the info....

How do I tell if it has an in-lens motor? The camera I have it on now does auto-focus; does that mean it has an in-lens motor?..

According tohttp://www.popphoto.com/...larphotographyfeatures/3979/new-whirled-order.htmlBut what about the glass made by companies such as Sigma, Tamron, and Tokina?.

Sigma is all over the D40. At this writing, it's website lists 17 lenses ranging from a 10-20mm to a mammoth 800mm that will work fine with the D40, since they have Sigma's HSM motor built in. The downside? These are all pro-level optics; not low-buck kit lenses geared to the beginner..

Tamron has yet to adapt any of it's lenses to the D40. Its Nikon mounts count on the camera's motor for AF. But I'm told that the company is on the case. Tokina is much the same..

For Nikon lenses, you need AF-S or equivalent (Sigma - HSM) if using D40 (or D40X, it seems), or AF-I apparently, if you want autofocus. If you don't mind manual focusing, this is less of an issue. It's also not an issue elsewhere in their line-up, ex. D80...

Dave,.

I had difficulty following the answers you got so I thought I would pitch in as well..

Any Nikon film SLR that is about 6 years old will have an F mount. So the lens will work on any Nikon DSLR. It will give you metering on any Nikon digital SLR. It will give you metering and autofocus on all past and present models except the D40 and D40x..

The lens will become the equivalent of a 42-450mm given the 1.5 x crop..

You do not say what the lens aperture is. If it is more than f5.6 it may compromise the AF system on your digital camera..

If you are looking to buy a cheap SLR your only option is the recently superceeded D50 (replaced by the D40/40x).Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.

Http://PlacidoD.Zenfolio.com/..

Thanks, Chris. That was very helpful (and a very clear explanation!)...