Originally posted by res3567 I recently found and dusted off my Super Tak M42 55mm 1.8. I have a T-mount adapter for my 500mm 8.0.
Just to be absolutely sure about this, you
do have two adapters,
don't you? M42 and T-mount have different pitches and so if you try to use one with an adapter for the other you are likely to mess up the thread (hopefully,
not the thread of the Super Tak).
Quote: I tried to mount the duo on my K10D and found that the lens will not screw all the way in the adapter and as a result the lens will not focus properly.
Ugh, that sounds like you are screwing the lens into the wrong type of mount. I hope you stopped before you did any damage to the lens thread.
Quote: I have searceed on EBAY and found thinner adapters ranging in price from $8 to $44. What is the best bang for my buck?
Again, I am not sure what you mean by "thinner adapters". The best adapter is the genuine Pentax adapter (use it
only with M42 lenses). I have found that the Kood adapter is a good copy, but it is important with the Kood (not the Pentax) that you remove the spring and screw that holds the spring. If you remove the spring then there is a danger that you can unscrew the lens as you focus, so this is not the best option, hence why the Pentax adapter is the best choice. In the UK the genuine Pentax adapter sells for about £25 used, which is the top of the range you quote in dollars. The Kood adapter is more like £10. (I think I paid £12 new.)
Whatever you do,
do not buy an adapter that has a flange that sticks out. The entire adapter must sit within the camera's K-mount and the face of the adapter must be flush with the front face of the K-mount on the camera. If you get an adapter with a flange then you'll not be able to focus at infinity.
Make sure that you do not get the T-mount and M42 mount adapters mixed up. It may be a good idea to keep the T-mount adapter permanently on the 500mm (even superglue it there) so that you never again have a chance of getting it on your Takumar.
Richard