To Remove Lens: (A) Extend lens by turning helicoid to closest focus position. (B) Press bayonet lock with thumb, and twist to left. (counterclockwise), Remove lens by pulling straight out. To Mount Lens: (C) Line up red dots on lens and mount. Insert gently to full stop. Twist to right (clockwise) until bayonet lock snaps closed. The interchangeable lens system of the Zenca Bronica Model S2 can be used with earlier model bayonet type Bronica cameras, The screw thread (diameter 57mm, pitch 1mm) shown in picture (C) is new with Model S2 and permits extension tube set and certain very long telephoto lenses to be mounted.