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11. APERTURE DIAPHRAGM ADJUSTMENT-
The proper opening or
setting
of the lens
aperture can
be determined
by use of an
exposure
meter. It is well to remember that the smaller
the
aperture,
the longer the
exposure.
In other words, if the
aper-
ture is stopped
down
to
the next highest
figure
,
the time
of
ex-
posure must be practically doubled.
For
example,
if the
exposure
meter indicates
an exposure
time of
1/
60 of
a second
with
f/
5.6 aper-
ture
opening, the time must be doubled
if
the
diaphragm
is stopped
down
to
f
/8. This
means that the shutter
speed
dial would then be
set on
1/
30 of a second,
which
gives a
longer time of
exposure
than
1/
60
of
a second.
If
a
moving object is to be photographed, it
is
quite obvious that you would select
a
short
exposure
time in order
to
stop the
object in motion. This would mean opening the lens to
admit
more light during
a
shorter
exposure
period. If, on the other hand,
you have
a still
object
and
there is no need for a fast
shutter speed,
you can
then
stop
down
your
diaphragm
slightly
and increase the
time of
exposure.
As
mentioned on page
6,
shutter speeds other than
lhose
marked on speed dials should not be attempted.
Note
that
TOWER
cameras are engraved
with the European system of
markings for
aperture and
shutter speeds
and,
in many instances,
exposure
meters
are
not marked to be used with this system. However,
the new TOWER meter is marked to be used with
either
the American
or European
system.
According to the
exposure
meter being used,
a
setting
of
f/
2
may be required on Hie iris diaphragm of the TOWER
35
mm
camera.
At the
same
time, the
exposure
time may be indicated
as
1/
480
of
a second.
In this
case
you
should
set the shutter
at
1/
500
of
a second
because there is no method by which we
can
set the shutter
at
1/
480
of
a second.
In
all
instances, there is enough leeway in the
film to
accommodate
these
small
discrepancies. If, on the other hand,
your
exposure
meter indicates that you set
the
time at 1/25 of
a second,
you can also set
your TOWER
35
mm
camera at
1/
20
of
a
second
and
be perfectly
safe
in
securing
the proper
exposure.
The differences
are
not
great enough
to make
any appreciable
difference in
exposures.
15
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