Shutter is used to control exposure, that is, the light passing into the camera. There are two types of design.

The first one is between-the-lens shutter made by leaf shape metal blades. It's opening and closing from and towards the center are controlled by two sets of spring, which tension is set for the timing. Due to its limitation to 1/500 sec. and its cost, only used in 4x5 and 120 format camera.

The second one is focal plane shutter for 135 camera. It is installed before the focal plane; that is why it is so named. It has been derived from the drop shutter, a very old design. There are two curtains; each controlled by a spring. The exposure time is controlled by the width between these two curtains. Basing on the effectiveness and in comparison with the between-the-lens shutter, a time is named. The shutter speed is not a real movement measurement, but its relative exposing value.

The curtain is made of cloth or light metal, with the cloth for horizontal travel and light metal for vertical travel. The maximum speed of horizontal travel is limited to 1/2000 sec. Vertical travel with a shorter distance, 24 mm instead of 36mm, and with light metal the opening can be changed to sections, therefore the speed can be raised to 1/4000 sec. or faster.