Originally posted by dokblues Hi: Can anyone tell me which other makers such as canon ,nikon,etc can be adapted to k mount??
Have never looked into other lens compatibality before.
In general, adapters exist for lenses that have a larger register distance (lens-to-film distance) than the donor camera. Canon EOS and Olympus 4/3rd cameras have very short register distances, which is why there are myriad adapters for other mounts. (There is a mount allowing Pentax K lenses to both Canon EOS and 4/3.) For Pentax K mount cameras, there are commonly only two adapters - one for M42 (Pentax screw mount) lenses, and one for Pentax 645 (medium format) lenses. Pentax designed the K mount with the same register distance as their popular M42 mount, deliberately making the mount compatible via a simple adapter. These can be found all over. The 645 Lens adapter is somewhat rarer but still fairly common.
In theory, and if you are brave, you can adapt either the Nikon F mount or Leica R mount lenses to fit your Pentax. This is because they are 1mm (Nikon) and 2mm (Leica R) longer from lens-to-film than the Pentax. Both of these would require taking off the original mount and replacing it with a 'donor' Pentax mount because there is not enough space to contain the bayonet on the Nikon/Leica R lens and still sit flush in the Pentax K mount. I've done such modification with some Nikkors but the Leica R lenses are too expensive for such experiments.
It is also possible to fit a Nikon lens cleanly inside the Pentax mount, but it does not lock (and some AI lenses don't even fit) and could easily come off depending on the lens.