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8. VIEWFINDER-
The built-in
viewfinder is
an optically
ground,
di
rect-vision
type of finder
and shows
the
approximate
field
covered
by
the lens of the ordinary 50
mm
standard
focal
length lens.
Be
sure
to
hold it le\·el with
the eye.
If
one were to look
on
a
bias through the
viewfinder
window,
it
might
not
show
the
entire
picture desired.
There-
fore, you must be sure
that
you bring
your
eye as
close to
the
viewfinder
as
possible. ( Len es
of longer
or
horter focal
lengths
available for the
TOWER
35 mm camera require the
use of the
Universal
Vi
ewfinder,
which
fits
into
the accessory shoe on top
of
camera (See
page 31)
9. EXPLANATION OF APERTURE DIAPHRAGM
A camera
lens
is very
similar
to the
human eye. When
the
eye
is used
in
a
dark
room
the pupil
becomes enlarged to
admit
more
light.
When
in
a
lighter
area,
the
pupil becomes small.
It
varies
according
to
the
intensity of light reaching the
eye.
The camera
lens
has
no
such
auto-
matic muscular
system, and, as
a
result,
it must be
mechanically ad-
justed
according
to
the
intensity of
light
on the object to
be
photo-
graphed.
This
opening
or
closing of
the
so-called
"pupil" or
"iris
dia-
phragm" of
the
lens is adjusted by the
use
of a
knurled
ring (Illust.
A-
Aperture
Adjustment Ring)
10. EXPLANATION OF APERTURE SCALE-
The
figures between
the
frontal knurled ring
and
the second knurled
ring
pertain
to
the
iris
di
aphragm
within the
lens
barrel (Illust. A)
They rep resent the
relative aperture openings
and
regulate
the
amount
of
light
to be
admitted
according
to the intensity
of
the
light
on the
subject to
be
photographed.
In
the case of the
f/2
lens
the
figures
are
as
follows-f/2
indicates that
the
lens
is wide
open,
f/2 8, f/4,
f!S.6,
f/ 8, f/
11
and
f/
16 represent
the remaining
openings. The
f!16
is the
smallest
possible
opening
with
the
f
/2 lens.
You
should
always
remem-
ber
that
the
size
of
the
aperture varies
in
indirect proportion to
the size
of the
number.
For
example,
f
/2
is the
smallest number,
but represents
the
widest
lens aperature
on
the 50
mm f
/2
lens
.
Conversely
f
/
16
re-
duces
the
lens
aperture to the smallest possible opening.
14
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