Comments about Pentax Pentax-m 45-125/4.0 Zoom Lens *58:

This is surprisingly sharp for a K era zoom. It has the SMC coating, so flare is better controlled than you'd expect from an older lens, but it is one of the old K series.

Surprisingly, it's sharp, even wide open. There might be a touch of distortion at 125mm, but you have to look for it.

No electrical contacts, so until Penatx decides to un-cripple the mounts on the digital cameras, you're limited to manual exposure or wide-open aperture priority.

It's a bit of a sleeper, though Pentax lenses have been snapped up quickly lately.

If you can deal with manual exposure, and want a nice alternative to the hyper-expensive 50-135 susper pro lens, go for it. I still use it with the *st D and the K10D.