19
EXPOSURE CONTROL
The amount of exposure the film receives is determined by a
combination of shutter speed and aperture. The larger the lens
aperture, the more exposure. Likewise, the slower the shutter speed
the greater the exposure. Aperture is expressed in f/numbers with
larger numbers representing smaller apertures and vice versa. For
example, f/8 gives twice as much exposure as f/11.
Camera aperture and shutter-speed controls are calculated so that an
increase of one f/number compensates for a onestep decrease in
shutter speed. For example, 1/250 second at f/4 is the same as 1/60
second at f/8. The table below shows how aperture and shutter speed
are interrelated. All the combinations give the same exposure.
The choice of aperture and shutter-speed combination depends on
the desired results. Use a fast shutter speed to freeze move~ent or a
slow one to create deliberate blur. Small apertures give greater depth
of field, large ones make the main subject stand out in sharp focus
and throw unimportant background out of focus.
Aperture f/2.8 f/4 f/5.6 f/8 f/11
Shutter Speed 1/500 1/250 1/125 1/60 1/30
(Second)
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