All Pentax K mount lenses made from about 1975 will fit current Pentax DSLRs.
There are a few incompatibility problems where other manufacturers have made their versions of the K mount, have a look at the bottom of this page -
http://www.robertstech.com/compat.htm
- but although I have read about these problems I've not heard of anyone who has had a problem.
As said, if it is an "A" lens, ie has an "A" after the highest f number then the camera will control the aperture. If not, then the lens will normally work at full aperture, but there is a workaround. This has useful information on the use of old K mount lenses -
http://www.robertsdonovan.com/?p=1181
You'll lose auto focus and this may be something that makes the use of an old lens too inconvenient. It is not as easy to manually focus with a DSLR as it was with 35mm film SLRs(normally there is no split screen), but with a bit of work it can be done.
The shot here was taken with a K5 and a 30 year old Sigma 70-210mm zoom.
There are plenty of old K mount lenses going for very little and as the IS is in the camera body with Pentax, all of these lenses become IS lenses.
A risk you take with old lenses is that they may fail, as my Sigma zoom has just done.
However, if you have some lenses and like the K30 it is a way of getting a bit more out of the lenses and the the current deal on the K30 is good.
Dave
