Canon CINEZOOM 512 - Manual (Page 12)

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.