Aperture
and
shutter
speeds
The
aperture
(or stop)
of
the iris
diaphragm
controls the
amount
of
light
falling
on the
film
and thus the exposure. It also controls
the depth
of
field.
Page
33
tells you
how
to
determine the depth
of
field
.
Note
that
the
largest
aperture
(f/l.5
with
the
NOKTON
and f/2
with
the ULTRON)
allows
the greatest
amount
of
light
to
pass
through
the lens. The successive numbers
of
the
aperture
ring
halve the
amount
of
light
from
number
to
number.
This means in
practic
e
that
in i
dentical
lighting
conditions you
mu
st
hoi
ve
or
do
ubi
e the shutter speed
from
stop
to
stop
either
way.
You
may
also
set
int
erme
diate
values, described under "Setting
the Shutter Speed
".
Setting the Aperture
Turn
the
aper
ture ring until the
selected
stop
is
opposite
the
white
index lin
e.
Th
e
whole
of
the
sca
le
is
clearly
visible
at
a
glance
from
above.
15