Originally posted by twitch All those lenses are manual focus only. There is a nice feature on all Pentax DSLR's though called "catch in focus" (CiF) which helps greatly getting in focus images. If I knew how CiF worked I'd explain it, but because I only own AF lenses I have no idea, but it's meant to be the cat PJs to the MF lenses owners.
If you have a manual focus lens, you can put the AF/MF switch on the camera either to MF and use the lens like a normal MF lens, or you can put it on AF.
If on AF, the shutter button won't work unless the center AF sensor (others don't work for some reason) confirms that there is something in focus.
So there is a strategy just to wait for the subject to move into focus while holding down the shutter button, or if the subject is too slow, to turn the focus ring slowly in the right direction until the subject is in focus and the AF sensor triggers the shutter.
i have some manual lenses, but i never really tried that method of focusing.
PS: you should also think about viewfinder magnification: all the entry level bodies (k-x, k-r) have pentamirror VF with smaller magnification which aren't as fun to use for manual focusing, so in your case an used "higher-end" body like k20d and k7 (i'm not sure about older bodies) may be better if you don't want to spend too much money
(my experience is based on a k7 and a k110d)