There are two types of M42-to-K-mount adaptor:
- The Flange type
- The Recessed type
Don't be like me and get the
wrong type, which is the Flange type. While the flange type is cheap, is commonly available and the flange appears thin, it is still thick enough to prevent focus at infinity.
Get the recessed type. I've got a "Roxsen" 3rd-party version. This is very easy to fit on a K100D Super body, but I find it is difficult to fit or remove this quickly on a K20D. The genuine Pentax M42 recessed adaptor is reported to be easier to fit compared to 3rd-party adaptors.
Here's some pictures I took showing the difference between the two M42-to-K-mount adaptors.
Recessed-type adapter plus insertion/removal key on left – Flange-type on right. Both showing the side that fits to the camera:
Flange-type fitted:
Recessed-type fitted:
Dan.