Originally posted by zx-m I thank you for the prompt response, Zewrak, as I was initially puzzled by this lens.
Your comments were very helpful, as I think I have figured out the matter. Yes, it does have a switch, marked "A," and when I switch it to the A side, the lens closes down (or opens up) properly. Actually, there are stops either way, but they are different than stops on more modern lenses...less distinct.
Regards,
Glen
Well I don't know that particular lens. But I suppose that if you are in manual mode you want it to move quickly and easily, since you will turn it while having it on the camera. Because focus can be hard to achieve at high aperture, since the image gets dark. So therefor you focus first wide open and then turn the aperture down.
On one of my lenses (Helios 44-2) for example there are two rings, one that sets the aperture and one that opens and closes the lens to the aperture you set with the first ring. The second ring has no resistence at all.
If you have "A" set, it means that the lens should be wide open while you focus and close down when you hit the shutter release button. When you have the "M" mode it should close down even if the lens is not mounted to a camera (the pin in the mount should not have any function when in M mode). Test it by setting the A setting and close the aperture as much as possible and then push the pin in the back, then it should close.