Small-Format Cameras, Continued
Focal-plane
shutters
Focal-plane shutters are essentially two light-proof cloth or thin metal
curtains in front of the film plane that move across the film in the same
direction. As the first curtain moves from one side to the other, the second
curtain follows. The speed at which the curtains move is called shutter
speed. When a slow shutter speed is set, the second curtain waits a relatively
long time and the space between the first and second curtain is wide.
Shutter
speed dials are located on the camera body and indicate time in fractions of a
second. Shutter, aperture, and mirror work together in a precise sequence
that repeats each time the shutter release trips. Most 35mm cameras have
focal-plane shutters. Focal-plane shutters simplify camera construction and
make interchangeable lenses smaller, lighter, and less expensive than leaf
shutters.
Figure 7-12 shows a focal-plane shutter.
Figure 7-12.—Focal-plane shutters.
Frame
indicator
The frame indicator is a small window near the shutter-speed dial that
displays the number of pictures taken. Each time the back of the camera
opens, the number resets to “0.”
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