While i am a specialized Pentax user, I also use other brand lenses with other kind of mounts.
Especially M42 and PK* lenses.
To do this, you need an adapter to convert M42 to K* mount ( * also referred as PK mount )
PK* lenses can be mounted without an adapter, but also with this type of lenses, there are many different kind of mounts -> electrical contacts, an A setting on the lens, a switch for manual/auto, metal latches in the mount and hand controlled apertures
Doing this for a while now, i came across a few problems.
But also if you have another brand of camera, you’ll need adapters and can come across coupling problems either electrical or mechanical.
For this I started this topic, and I will complement the article depending on problems I encounter.
Link to the new topic https://www.digicrea.be/the-classic-camera-project/old-lenses-on-new-cameras/