I just got a Cowboy Studio adapter to fit Pentax lenses to the NEX5N. The two lenses I have tried so far are the 43mm Ltd. f1.9 and the 77mm Ltd. f1.8. Both work fine with this setup. The adapter is rather large. That is it is larger than any pancake lens by itself, so the whole rig pushes the lens further out than one would hope. Nevertheless, with the help of the peaking feature, it focuses flawlessly. Here is one taken with the 77mm through chicken wire using peaking to get the rooster in focus and ignore the wire, a difficult task for auto focus. The shutter speed was 1/60th at f1.8 and 320 ISO.