The basics of exposure – Canon A-1 User Manual
Page 54
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The Basics of Exposure
This
section
contains
some
terms
and
definitions which will be used throughout
this instruction booklet.
The amount of exposure is a matter not only
of the amount of light allowed to strike
the film but also of the amount of time
the light is allowed to strike the film. The
camera
has
two
mechanisms
to
control
exposure,
the
diaphragm
and
the
shutter.
The
diaphragm
consists
of
blades
which
open
and
close
to
certain
size
openings
called apertures. The size of the aperture
determines the amount of light which will
fall on the film. The various size apertures
tire indicated by a set series of numbers
called
f/stops
or
f/numbers.
Each
f/stop
represents
some
amount
of
light
that
is
allowed to pass through the lens. The smaller
numbers are called large f/stops while the
larger
numbers
are
called
small
f/stops.
This is because the larger numbers represent
smaller apertures and allow less light to pass