Movies for TV - Early Television Foundation

140
FUNDAMENTALS
in the finder, exactly what appears in the finder will be photographed,
since the is aperture the same as a standard 16 mm
sound film aperature.
The view finder coupled to the lens has been left until now
since it is in a way part of the full-frame follow-focus system.
There are many types
of view finders. Since each one has its dis-
advantages as well as advantages and the model chosen usually
depends on the finances of the purchaser, only a general description
will be given. It will be obvious that each lens will require
a different objective and frame indicator since the field of view
will differ with each. Some achieve this by inserting a different
mask into the finder, others by hairlines or lens' changes. In the
coupled type, parallax has to be overcome since the two lenses
are on two separate axes and as the subject approaches the camera
the finder will have to converge toward the axis of the filming lens
to ensure that the same field is covered by each. This produces
another complication.
The purpose of the shutter in the camera has already been
discussed, and it only remains to describe the methods whereby
its speed may be effectively varied. It might be thought that be-
cause the speed of the film is constant at twenty-four frames per
second and therefore the mechanism operates at a constant speed
it would be impossible to vary the shutter speed. The movie
camera for 16 mm use normally has a 170 shutter: that is, it is
open for 170 out of the 360 of a full rotation. In this case, at
twenty-four frames a second the exposure is 1/50
of a second.
Therefore, all normal exposures are calculated at this exposure
speed. For most purposes, this is fast enough to prevent blur when
photographing moving objects. Some cameras have a dissolving
shutter which makes it possible to control the amount of shutter
opening without varying the speed of the camera mechanism. For
instance, in the Maurer camera the dissolving shutter will open
to as much as 235 giving an exposure time of 1/35 second. This
means that in conditions of poor light the equivalent of an extra
half stop is obtained. It will be apparent that changing the shutter
speed will change the aperture required in most cases; the in-