Movies for TV - Early Television Foundation

change occurs. The grain
PRINCIPLES OF MOVIES 11
of the emulsion becomes coarse. The
silver salt in the emulsion is, of course, composed of millions of tiny
particles. These particles constitute the grain of the film. If the film
is enlarged many times these particles become visible and impart a
"grainy" appearance to the picture.
This is similar to what is seen
if a half tone reproduction is examined with a powerful magnifying
glass.
The cameraman has to decide between a fast film with coarse
grain and a slower film with finer grain. In studio conditions where
the lights can be adjusted as required, a slow film can be used and
optically perfect pictures obtained. It is often apparent
in newsreels
that a faster film has been used to catch action that occurred in
poor light. In addition to the poorer definition and loss of detail in
the faster film, one other drawback is encountered : this is extreme
contrast. High contrast and loss of detail go hand in hand. This can
be seen by watching newsreel pictures of a fire or other unexpected
happenings after dark. The blacks and whites are vivid and in the
white areas there is little detail.
The types of film in general use vary considerably according to
the purpose for which they are to be used. For movie work, panchromatic
film is very popular although it is considered by some
technicians to possess a small drawback in that it has a very slight
color in the base. Panchromatic film is sensitive to all colors
grayish
and thus always has to be handled in complete darkness, whereas
the much slower orthochromatic film can be developed in a red
light. However, since it is not usual to develop film in containers in
which they can be seen unless it happens to be a short test-piece
in a bottle this is not too important. But this high sensitivity is
important in the case of handling new reels of film to be placed in
the camera. It is comparatively easy to fog a considerable amount
of film by careless handling in bright light. Orthochromatic film is
the slowest normally used for film work. The color limitations of this
film make it possible to perform some very interesting and useful
trick effects. For instance, it is not sensitive to red, and blue photographs
extremely light. By taking advantage of these effects and
using certain filters, many tricks can be performed. The Super-XX