I'm looking at a bellows for my A350. What I'm thinking is getting an old SR mount bellows and using an alpha to MD adapter for the camera and an MD lens. How do I stop down the aperture on the MD lens? When you move the aperture ring, does that actually move the aperture or (when attached to an SR mount camera) just set a stop that the camera mechanicals stops down just before the shutter opens? - Thanks, TF