Originally posted by stevewong The problem is not with the adapter {it is fine} - it is with the lens {or your use of the lens}. The little pin in the back of the lens controls whether it responds to the aperture ring; out it is always fully open - it responds to the ring only when the pin is pushed in. Asahi's {company that created Pentax} M42 lenses had a 'man/auto' switch - the lenses acted in exactly this way when switched to 'auto' and always followed the aperture ring when switched to 'man'; this lens seems to always be in 'auto' mode. I suppose you could use a tiny piece of tape to hold the pin in, but I'd be afraid of the tape's coming loose and falling inside the camera. Some original M42 cameras pushed the pin in only as you took a photo; that way, you could focus with the lens fully open {thinnest area in focus}, but got the aperture you asked for when you needed it.