Thanks for the helpful comments everyone. I've learned a lot. And it seems my troubles may not be quite over, as I've also bought a couple of wides, 35/3.5 and 28/3.5, both Super Takumars. If infinity focus is more critical for wides, I might run into more trouble. However there are no problems like this that can't be solved, so I'll see what happens with them. At the moment I'm torn between the internal adapters like the Adapter K, and those that stay on the lens. As Mike said, it's easier when using both PK and m42 lenses.

I measured mine this morning and it's only 0.62mm in thickness - hard to imagine anything thinner, and possible even thinner than the ones above. It seems that the genuine Adapter K is the best option. I'm assuming that this one stays in the camera and that other m42 lenses screw into it, rather than having a separate adapter for each lens? As I've just purchased a couple of wide angle m42 lenses (not yet arrived) and this would probably work out cheaper.

Thanks, I had the same comment from Fotodiox - they suggested that I return it and ask for a replacement. They said: "Most of our adapters focus to infinity before the infinity focus mark on the lens, if this is not the case maybe the is an issue with the adapter". I'm a bit surprised they admitted the possibility the adapter may be the problem.

Just found the answer to my question. I saw the Shop tab on the menu bar. I'll try there for a Pentax Adapter K.

Thanks Mike and John. I was pretty sure the fault was with the adapter. I note that some adapters get around this problem by incorporating a lens element to achieve infinity focus, namely the Fotodiox adapter for Nikon cameras. This utterly defeats the purpose in my opinion. I would never compromise the performance of fine lenses by putting cheap glass in the optical path.

Can I ask if there is a place online where one can buy Pentax accessories. Our local agent in Australia has been useless for decades, and from all accounts continues to be so.

Many thanks,

Barry

Hi all, I'm new here and haven't been able to find help with this via a search, so here is my question: I have just bought a Super Takumar 50/1.4 in m42 thread mount. I recently learned what a legend this lens is. I just received a Fotodiox m42-Pentax K mount adapter so that I could use the lens on my MX. To my disappointment I found the lens wouldn't focus at infinity. My Takumar 50/1.7 works perfectly on the camera of course. My feeling is that the adapter, although thin, is too thick and holds the 50/1.4 too far out from the mount to allow infinity focus. The lens itself appears superb; focuses smoothly right to the infinity mark. Has anyone here had this specific problem? What is the consensus - lens, camera or adapter? I've sent off an email to Fotodiox and haven't had a reply, but I'd be surprised if they said it was their adapter. Thanks for your thoughts.

Barry