Variable shutter control – Canon CINEZOOM 512 User Manual
Page 12
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VARIABLE SHUTTER CONTROL
The film stops
An advance of
for exposure.
the exposed
frame
places.
takes
FILMING SPEED AND SHUTTER
The
8mm
shutter
is
closely
connected
with the film advance.
The
exposure
is
made
from
the
rotation
of the semicircular leaf which has a given
angle.
When
the
leaf
is
rotating,
expo
sure
of
one
frame
and
film
advance
are
coupled,
moving
synchronously.
In
other
words, when the open section of the leaf
is
at
the
aperture
section,
the
film
stops
for
exposure.
The
principle
of
this
process
is that when the aperture section is block
ed by the rotating leaf, an advance of the
exposed frame takes place.
The
term
16
frames
denote
that
in
one
second,
15
frames
are
exposed
and
ad
vanced,
while
32
frames
would
mean
that
the speed will be doubled. Hence, the ex
posure
time
is
determined
by
the
open
angle
of
this
leaf
and
the
rotating
speed
and
is
regulated
by
the
filming
speed.
Frame speed 8
12
16
24
32
48
64
Exposure (sec.) 1/18 1/26 1/35 1/50 1/70 l/lOO 1/140
ADJUSTING
THE
8mm
CAMERA
FILM
SPEED
Putting
aside
the
8mm
at
this
point,
let
us
consider
the
film
speed
adjustment
of
the
ordinary
camera.
For
a
fast
moving
object,
a
fast
shutter
speed
is
selected.
In a dark room, the slow shutter is properly
adjusted
and set in
open position. For an
ordinary
camera,
shutter
and
diaphragm
are freely adjusted together.
However, in the case of the 8mm camera
the filming speed cannot be changed at will.
The
reason
is
that
the
standard
speed
is
fixed
at
16
frames.
Because
under
normal
conditions, the shooting of the film is done
on
the
basis
of
16
frames
and
projected
at the speed of 16 frames, change of speed
should
be
made
only
when
you
intend
to
take
special
types
of
movies
such
as
trick
shots.
In
other
words,
the
exposure
ad
justment
is
not
done
by
changing
shutter
speed,
but
is
done
by
adjusting
the
diaphragm.
EXPOSURE
ADJUSTMENT
WITH
THE
VARIABLE SHUTTER CONTROL
Instead
of
relying
only
on
the
diaphragm,
the
variable
shutter
control
enables
the
change
of
exposure
to
be
made
with
the
shutter.
As
explained
earlier,
the
exposure
time
is
determined
by
the
open
angle
of
the
shutter.
By
changing
the
degree
of
this
angle,
the
exposure
time
is
reduced.
Although the ordinary 8mm camera has the
shutter opening angle fixed at around 150°,
in the case of the Canon Cine Zoom 512
the angle may be changed to any of the
four stages between 155° to 0°. It is pos
sible,
therefore,
to
freely
make
exposure
adjustments.
In
addition,
fade-in
and
fade-
out may be easily carried out.