Movies for TV - Early Television Foundation

FILM TRANSMISSION EQUIPMENT 95
"maintained." Only too often the projectors are not properly in-
spected and given regular preventive overhauls.
Even the best print obtainable will not produce good pictures
and sound if the machine in which it is used is not properly ad-
justed. For instance, wows in the sound are bound to occur if the
sound head and guides are allowed to become dirty or distorted
so that film motion is impeded. For relatively simple productions,
16 mm film is generally cheaper, more convenient, and as good
as 35 mm, but for elaborate affairs where many "super effects"
are required, it is better to use 35 mm, merely because the equipment
for making these effects is available and has already been
developed to a high pitch of perfection.
As far as projectors for theatre or semi-professional use are
concerned, there is nothing very difficult about their design. How-
ever, when the question of using them to project movies over television
is considered, a number of problems become involved. The
ordinary requirements of a rock-steady picture plus perfect clarity
of focus and adequate illumination are complicated by the neces-
sity of converting the frame repetition rate from twenty-four
frames a second for movie film to thirty frames a second for tele-
vision scanning while still producing superlative picture quality.
Before proceeding to discuss the television problem in greater de-
tail, it would be advisable to show how the average projector
operates.
Actually, the operation
with the difference that instead of using an exterior light to form
is the reverse of the camera function
a picture which is focussed onto film, an interior light is used to
shine through a film and produce a picture on a screen.
It will be recalled that the film taken in the camera consists of
a series of pictures taken at the rate of twenty-four frames (or
pictures) a second, each one being very slightly different from the
preceding one. The film does not pass continuously through the
camera but pauses for a fraction of a second while the exposure is
made. In the projector the film passes through in the same inter-
mittent manner, and a shutter cuts off the light between each
picture as it is moved down. If it were not for this shutter, a blur