If you have a set of old M42 thread mount, manual focus Asahai, Takumar, or Vivitar lenses, and a newer Pentax digital camera like a K10 or K20, this little ring will allow you to mount your lenses in the KAF bayonet mount camera body. There are good and bad points to this mount adapter. First the good:

1. The machining is not great, but adequate to the task. It's a little rough looking, but the threads and the bayonet do fit properly.

2. The price is reasonable, in that it does allow you to continue to use obsolete lenses that you may have originally paid hundreds of dollars for.

3. This mount is a true "internal" adapter ring with no surface flange, so you can acheive infinity focus. Some other M42 to KAF adapters on the market have a 1 mm thick flange that offsets the lens just enough that you cannot focus it at infinity.



The bad points:

1. This adapter has a spring loaded tab that locks it into place in the camera body. If you lose the little tool that comes with the adapter, you will probably not be able to remove the ring from the camera body. I recommend removing the locking tab (it's attached to the ring with a tiny screw), which allows you to leave the ring attached to the lens instead of the camera. Removing the locking tab also means that you no longer have to use the key-tool to remove the ring, so it's not a disaster if you lose or misplace it. In my K20, the adapter ring's bayonet tabs are a fairly tight fit, so little or no danger of the ring backing out by itself.

2. I don't think that this ring is made of a very wear-resistant alloy, so I feel that there is a possibility of the threads or bayonet jamming at some point. Use this ring with caution, and for heaven's sake don't force it the first time; If you feel an undue amount of friction at the first-time use, either in the threads or the bayonet, back off and see if the threads or bayonet are simply dirty or if they are rough and badly machined.

3. Acheiving sharp focus with these old lenses in the viewfinder of a modern DSLR camera, can be an exercise in frustration, especially at wide open aperture. If your camera has a zoom-able Live View mode, like the K-7, and you are shooting from a tripod, you will get better results with live view.



Recommended only if you have a really nice or expensive (specialty M42) lens that you can't afford to replace with an auto-focus lens. I use mine with an old Asahi 50mm f1.4 "M" lens.