I will soon be purchasing a Pentax K200D, I have been on eBay buy older film cameras, I now have a ZX-L, ZX-7 and a K1000. So that leads me to start looking for lenses. EDIT: (The K1000 has a 50mm 1:2 and I got a Pentax 35-80/4 AF with the ZX-7) I see many I like, not knowing much yet, I am noticing that a lens with a lower apeture number seems to be desirable? Like a 28-70/2.8-4.5 is better than a 28-70/3.5-5.6 ? Is this correct? I find a few primes made by Pentax that are very affordable, as well as some older manual focus lenses, but when I get to choosing something in autofocus, the price goes up considerably if the lens is a Pentax. I see Sigma lenses with similar specifications for MUCH less, I'm sure you get what you pay for, but do you get some bang for your buck with a Sigma? (or any other brand for that matter).