By far the worst lens I have ever used. Took me 10 minutes to figure out it was a total dud. Does not focus at all in the mid ranges. hunts like hell to focus all other times. I've never seen a lens this bad. I just ordered a 80-200 AF-D to replace it. Perhaps when the Pentax version comes out these issues will be fixed. I could tell at the house the AF was slow but I was assuming it was the extreme low light, and close focus. Bottom line, this is a dud, unless I just happened to get a bad copy that matched the reported problems on the other review sites.