Movies for TV - Early Television Foundation

48
FUNDAMENTALS
isfactory for they have a habit of running down at crucial
moments : the spring is not powerful enough to expose a full magazine
on one winding; the speed varies despite the provision of a
governor which helps to maintain a constant speed, and for lip
sync work it is obviously utterly useless because it will not lock
in with the sound recorder.
In spite of the imposing list of reasons why spring
drives are
no good, they are used a great deal and are invaluable, provided
the limitations mentioned above are kept in mind and they are
used for the purposes for which they are best suited. Newsreel
cameramen working away from sources of power, photographers
who must carry a minimum of weight, brief clips of film which
are known in advance to be short, such as single-frame work for
animation, can all make use of a spring motor. Since most shots
should run at least seven seconds, it is normally possible to get
two shots or a single, longer shot on one winding without any
danger. It is always advisable to rewind the motor between each
shot if possible, for in this manner the speed remains more con-
stant through the length of the exposure.
Electric motor drives are made in three general forms,
although there are, of course, variations in each class of motor
drive. The first type is the synchronous motor which operates
on 110 volts, alternating current, 60 cycles only (or other fre-
quencies to special order), with a constant speed
of 24 frames a
second only. This motor is used for all types of production in general
and in particular for lip sync filming, where the picture film must
run with an unvarying speed at all times. The second kind is the
"wild" motor which operates from 110 volts of alternating current
or direct current. This is a series-wound motor and the speed can
be adjusted within very wide limits: it is used for any kind of
work where sound does not have to be synchronized with the pic-
tures. The last category includes the 12-volt or other low-voltage
motor which operates from batteries either storage or dry
batteries strapped around the waist of the operator. The battery-
operated cameras are used in much the same way as the springdriven
types except that they are capable of exposing many