This is one of those good news/bad news stories. I'm typically very fond of Yashica lenses, and I had always heard good things about the DS-M series; so when a 50/1.4 presented itself at a good price, I promptly bought it. But when it arrived, I wasn't terribly happy about that decision, for several reasons. The first impression wasn't all that positive; the overall build quality seemed to be a step down from the lovely DX lenses. Then - and I understand this is very common with the DS-M series - the rubber focus ring immediately detached itself. OK, I said, I can fix that. So I screwed the lens into my flanged M42->K adapter (there's no auto/manual switch, so for use on a DSLR, a means must be contrived to keep the aperture pin depressed), and discovered that, because of the way the aperture mechanism works, the adapter flange didn't depress the pin far enough to enable the entire range of f-stops - f4 was about as low as I could go. I searched in vain for a simple way to remove the lens mount, so that I could modify the auto-aperture system. Finally, growing more and more frustrated, I unscrewed the rear element, and the pin mechanism was revealed. But getting at it, and figuring out how to disable it, was, to say the least, challenging. After half a dozen unsuccessful efforts, borrowing nearly every tool from my other hobby - fountain pen restoration - I finally managed to work a length of wire insulation around the pin, keeping it depressed. Feeling better about things, I carefully reglued the focus ring, and set out to take some pictures - not really hoping for much, after all that. Well, that's the bad news. The good news is that the lens turns out to be optically excellent, with plenty of sharpness, wonderful color and lots of character. I still don't think its build quality matches that of the earlier Yashinons, but I'm delighted to say that (in my view at least) the results justify all the effort.