Most 50mm lenses from the film era (actually most lenses of any focal length) have to be stopped down somewhat to achieve their sharpest performance. I have an adapter with three different positions for aperture control. Open, somewhere in the middle, and stopped down. I bought this for use with relatively modern lenses that do not have their own aperture ring, but were designed originally to be adjusted via the camera. Does 'stopping down' the aperture via the adaptor have an effect on the lens sharpness performance similar to stopping down using the aperture blades within the lens itself? Is it optically the same in effect (leaving aside the difficulty of working out what f/stops the adapter settings are equivalent to, which is a different issue)?