I have as low a budget as you can imagine. At the moment I'm looking at some old Nikon lenses, I've also heard from some friends that Pentax K lenses are a bargain but are they any good? I'm not aware of Pentax's reputation. Are there any others worth really looking into? Obviously there are I just want to know which. I want a 50mm next but with a decent focus ring and manual aperture, which I'm assuming most vintage lenses have, it's just the worry of not being able to get a follow focus on there.