Aperture

On this lens, aperture is not automatic diaphragm, and because of darkness, focusing is too hard unless aperture is at open aperture. So,

1. Set a desiable aperture value on the aperture ring against at the triangle figure shown in the red circle.
2. Turn the lever in the blue circle till it stops.
   (By this, aperture blades open at open aperture.)
3. And at the same time, focus the subjet.