I just bought this lens (MC Cosinon-T 200/4 Cosina), I paid $7 plus $8 shipping, it looks in great shape, clean, almost new and when I move the aperture lever, it opens it fine. It focus well, but when I try to stop it down with the green button, it cannot be stopped down. It always shoot with wide open. I know the aperture is working because it manually open and closes. I a using the Pentax K5. Any advice?
PS. I also bought the same lens from a pawnshop for $1, but it was damaged, the focus was loose, and the aperture lever did not open the diaphragm.
I really appreciate your advice, the photos wide open are OK, as far as i can see in the short period of time at night.
Here is the lens.
Last edited by Pepe Guitarra; 07-09-2012 at 09:11 PM.