I went through several of these lenses before I found one which would focus properly on a IIIf. I tested the lenses with the camera on a tripod using a newspaper want ad page three feet awat as the target. The lens which did work properly was an 1950's vintage model with the silver barrel, neither of the later black barreled lenses was close to correct focus. I was dealing with a reputable Russian vendor (Alex) who provided a refund with no questions asked for the defective lenses.
The lens which I kept is slightly soft wide open and quite sharp down two stops. I find this a useful combination for portraiture, particulalry at this focal length. This lens performance is somewhat similar to an uncoated 85mm Serenar I once owned.
I wonder if there are three different variants extant for this lens. There are the ones which are grossly out of calibration, probably because a previous owner did some meddling. DAG has been quoted as saying that the focus cam motion of the Jupiter-9 is incorrect for a Leica rangefinder (won't focus properly at all distances) yet there are a number of people, such as those contributing to this thread, who find that their lens does work properly. It may be that the incorrect cam motion on some of the lenses is a manufacturing defect from the factory.
Cambridge Camera at one point recently was offering new Jupiter-9's on Ebay. When I contacted them regarding potential focus problems, they refused to guarantee that the lens would ork properly on a Leica.
