Originally posted by vonBaloney I think they look at big old zooms (usually worthless) and are impressed by the size and think they are worth something and some small prime they let go for less because it doesn't look like much. But unfortunately mostly people just mark everything way too high.
There are big old zooms that are worth going for though, I recently picked up a Komine made Vivitar Series 1 70-210mm f2.8-4 at a local thrift store. Came in a box with a K1000 with an M 50mm f2 mounted, an M 28mm f2.8 and an M 35mm f2.8. The Vivitar, the 28 and the 35 are all perfect, didn't notice until later that the 50mm has some nasty fungus, but I really didn't care about that one. There was also a Vivitar 2x teleconverter, which I have gutted to make an extension tube, a Vivitar 285HV that is digital safe at 8 volts and some other random stuff like filters and a flash bracket.
I didn't know anything about the Vivitar zoom and didn't know if the flash was safe, but I figured the 28mm and 35mm were worth the asking price of $95, so I jumped on it. When I got home I realized that the Vivitar was more than worth the asking price alone and the nice primes and everything else was just a bonus.
One thing that just occurred to me, the 50mm was the only one with fungus, it was mounted to the camera and in one of those "Eveready" style cases. I would almost bet that is what caused it by trapping moisture, since all of the other lenses are clean. A while ago I picked up a Rexatar 135mm f/2.8, it was in one of the faux leather cases, it also had fungus that caused haze. So I'll be more wary of any lens in a case, especially one that smells like a musty old attic. I should have noticed the fungus in the Rexatar, but I was more interested in the Super Lentar 21mm f3.8 that was being sold with it, identical to a well regarded Vivitar lens, which was totally clean.
If anything, a bad lens, as long as it is cheap enough, can be a great learning experience. You can attempt to fix things like stuck aperture blades, gummy focus helicoids or even try cleaning the fungus out of one. If you fail, it isn't a big loss and you have some spare parts for later. That Rexatar has given up the ball bearing that makes the aperture ring click to replace the one I lost while repairing a tight aperture ring on my Vivitar 200 f3.5.