Got my hands on a Porst 135mm f1.8! A lovely fast lens, well suited to my taste in exotic glass. A little soft wide open, incredibly difficult to focus, so shooting a series in rapid succession and picking the best. This is the PK version, and the Pentax to Canon chipped (for focus confirm) adapter needed significant back focus adjustment, and is still way off at minimal focal distance. When the lens arrived from Germany, the focus mechanism was very stiff, and hardly moved at the infinity end. Fortunately this has loosened but with use. Conclusion: New favourite for street photography and low light.