Minolta XG-7 - F U N D a M E N T a L S

EXPOSURE.CONTROL
FUNDAMENTALS
The
two
camera
exposure-control
settrngs
are
lens
opening
(aperture)
and
shutter
speed.
The
size
of
the
aperture
determines
the
amount
of volume
of light
reaching
the
fi
lm from
a
given
subject
and
lighting.
The
shutter
speed
determines
the length
of
time
this
light
acts
upon
the film.
Apertures
are
expressed
in
f-numbers,
which
are larger
for
small
openings
and vice
versa
(e.g.
,
f
116 represents
a small
opening,
f
12 a large
one).
Shutter
speeds
are
expressed
in
seconds
or
fractions
thereof,
which
are
generally
the
reciprocals
of
the
numbers
,
shown
on
shutter-speed
scales
(e.g.
60
=
1/60
sec.,
and
2
=
112
sec.).
At
usual
apertures,
each
f-number
setting
(e.g.,
f/8)
lets
in
twice
as much
f ight
as
the next
numerically
larger
one
(il,1
11
and half
as much
as
the
next
smaller
(f/5.6).
Similarly,
each
shutter
speed
(e.g.,
1/60
sec.)
allows
light
to
strike
the film
twice
as
long
as
the next
higher
speed
(1l12Sl
and half
as long
as
the next
lower
one
(1/30).
The
interval
between
two
standard
f-numbers
(say,
f
/4
and
t15.6l
or
shutter
speeds
(say,
1/15
and
1/30)
is
one
"stop."
Total
exposure
on
the
f
ilm
is
determined
by
the
combination
of
aperture
and
speed.
Other
things
being
equal,'using
the next
smaller
f-number
(i.e.,
giving
one
stop
more
exposure)
will
balance
using
the
next
higher
shutter
speed
(i.e.,
giving
one
stop less
expo_
sure),
and so
on.
A
great
range
of combinations
(e.9.,
f/5.6
at
113O,
f
14 at 1160,f
l2.B at 11125,
f
12 at
11250,
etc.)
wiil
thus
yietd
the
same
total
exposure.
The
specific
combination you
choose
under
given
lighting
conditions
will
depend
upon
the degree
to
which
you
want
the
greater
depth
of field
(see
p.
36)
of
smaller
apertures
and
the
greater
movement-blur
preventing
abili_
ty
of faster
speeds
(p.
28).
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