There are many adaptors on the internet converting M42 lens mount to any DSLR you can imagine. However, not all work well with old lenses from SLRs like Zenit, Practica or Pentax. Functionality differs from one DSLR brand to another and there are also many different types od adaptors. Following table is extract from internet forums and is comprehensive look at M42 adaptor possibilities.
|FFD||Focus to infinity||Focus confirmation||Metering||Anti-shake|
* electronic adaptor
** confirms focus, whether the object is in focus or not
- Canon - buy only adaptors with stop-screw or you can damage your DSLR
- Olympus - focal length and aperture setting only by programming adaptor chip
If you have lots of M42 lenses and you want to shoot with them with your DSLR, then you probably should buy some Pentax DSLR. Quite good functionality is also offered by Canon DSLRs. But it’s important remember, that if you use old M42 lenses you must use manual focus all the time and with many DSLRs also use fully manual mode.