ZS:

SLR lenses for M-42 screw thread

 

The manually focusable ZS lenses (for M-42 screw thread) are equipped with a push pin in order to close the aperture. Furthermore, they are equipped with a locking switch to change from manual to automatic aperture control. Due to this, the lens can be comfortably stopped down to working aperture when used with an adapter. The aperture priority can be used as well.