I recently came into possession of a very nice old M42 mount Pentax-M 135mm lens. I sent off for and received an adapter, but when installing the combo, I discovered that the lens will not focus to infinity. If won't even come close! More like about 6-8 feet is maximum. It's as if an extension tube had been installed. After looking at the adapter and studying it for a while, it would seem to my untrained eyes that the lens, when attached to the adapter, SHOULD be set back INTO the body somewhat, like it would if the body had a threaded mount. Does that make sense? In other words, the lens, when fitted to the adapter is far to far forward for it to focus properly. Would I be correct in assuming that I got either the wrong adapter or one that was not the one I really needed? Or was it just a cheapo and I got my money's worth?