Canon DS-8 - Manual (Page 30)

Variable Shutter Control
Variable Shutter and Filming Speed
The shutter of the 8mm movie camera is closely connected with the
fiim advance. The exposure is made from the rotation of the two
semicircuiar ieaves which have given angies. When the leaves are
rotating, exposure of one frame and film advance are coupled, mov­
ing synchronously. In other words, when the open section of the
leaves is at the aperture section, the film stops for exposure. And
when the aperture section is blocked by the rotating leaves, an ad­
vance of the exposed frame takes place. Hence, the exposure time
is determined by the open angle of these leaves and the rotating
speed, and are called variable shutter angle and filming‘speed
respectively.
Exposure Adjustment with the Variable Shutter
For a still camera, shutter and aperture are freely adjusted for the
exposure adjustment. However, in the case of an 8mm camera the
filming speed cannot be changed at will since the standard speed is
fixed. Because under normal conditions, the shooting and projec­
tion of the film are done at the standard speed, change of speed
should be made only when you intend to have special effects such
as faked shots. In other words, the exposure adjustment of the
movie camera is not done by changing the shutter speed but by
adjusting the aperture.
Instead of relying only on the aperture, the variable shutter enables
the change of exposure to be made with the shutter. By changing
the degree of the open angle of the shutter, the exposure time is
reduced. Although the ordinary 8mm camera has a shutter open­
ing angle fixed at around 160°, the angle of Canon Zoom DS-8 may
be changed to any of the four stages between 165° to 0°. It is
possible, therefore, to make exposure adjustments freely and
perform fade-ins and fade-outs.