Quote: Oh, and I was thinking, I saw that some guy once put alot of extension tubes back on a m42 lens so that the camera wouldnt crop the image, will this work?
The extension tubes will limit how far you can focus, and so aren't really useful for what you want.
I've had good results with a Pentax smc-A 28mm f/2.8 - reasonably easy to focus, and has a decent DOF. With a 24mm you'd get more of the same...
Whatever the brand, if it has a K-A mount your shooting will be faster as the metering and stop down stuff is all taken care of. In some ways the M42 lenses are MORE convenient than the M K mounts, as you can leave the camera on AV and simply click the aperture ring down to where you want it... The K mount will stop down for you but you'll have to meter manually, which can slow things down a bit (depending...)
Do you have the kit zoom? If you do, which focal length(s) do you like for the kind of shooting you do - I'd look into a prime of similar length. OTH if the kit doesn't go wide enough for you, then look for one of the ultra wides.