Facts about film (1948)

foreign [Applause] this is 16 millimeter sound film because it's easily shown on small portable projectors its invention has greatly increased the use and value of motion pictures these days anyone can operate a sound projector the film is a Celluloid strip perforated along one Edge a gelatin coating on one side contains the images of pictures and recorded sound on black and white film these images are formed of silver and on Color Film they're formed by dyes Celluloid unfortunately is not the world's strongest material therefore Motion Picture film must be handled with care to protect it from damage you see what I mean let's take another example care must be taken to protect film in transit here's a strong fiber box but see what's inside if before we ship a reel of film we apply a paper band and fasten it securely at the other end of the line we'll have film not spaghetti there are two types of Celluloid used in the manufacture of film one of them known as cellulose nitrate is the kind used for the 35 millimeter print shown in the movie theaters nitrate film is comparatively strong but it has the disadvantage of being highly inflammable it is almost an explosive theaters are required to maintain elaborate precautions against fire and to employ highly skilled operators this is just one of many reasons why it would not be safe to use nitrate film in a portable projector all 16 millimeter film is made of acetate cellulose acetate film is perfectly safe but it's not as tough as nitrate any friction against the surface of moving film is likely to produce a scratch it shows on the screen as a dark vertical line like this and this and this hey there get your fingers off the film that's better the manufacturers of 16 millimeter projectors carefully design their machines to keep film wear and strain at a minimum but in running through a projector the film necessarily touches and rubs against parts of the machine here at the gate for example the film is pressed between two pieces of metal the aperture plate and the pressure plate but see how these plates are made a wide path has been hollowed out for the pictures to go through and another has been made for the soundtrack the important areas of the film are not touched at all other parts of the machine the guide rollers sprockets and the sound drum turn with the film and so there is no friction in spite of the manufacturer's care scratches sometimes occur in the machine careless threading is one cause here for example the operator is allowing the film to scrape the bottom of the lamp house see those guide rollers that's what they're for film runs through the gate at the rate of 36 feet a minute dust and particles of gelatin are accumulating on the surfaces of the plates eventually the hollowed-out spaces are filled with dirt and so we have more of those lovely scratches before every reel of film The Wise operator uses a brush to clean out the gate at regular intervals he inspects the gate for hard particles of gelatin that the brush could not remove he scrapes them off with a toothpick he does not use a knife blade or a pin a metal tool would spoil the polished surface of the plates the operator also cleans the sprockets and checks the guide rollers to see that they turn freely while we're talking about scratches here's another way to make them the film is wound too Loosely on the Reel we think it ought to be tightened so we grab the Reel firmly and pull the film good and hard this is called cinching the film and the scratches we get are called cinch marks they look like this it's better to leave the film loose than to tighten it by cinching the perforations along the edge of the film provide the means by which the sprocket wheels of the projector move the film here the operator has been careful to mesh the film preparations with the sprocket teeth but a bad splice in the film may cause the perforations to jump out of alignment with the teeth and so new holes may be punched where they don't belong it's easy to check for this sort of damage while the machine is running gently feel the perforated edge of the film as it passes into the take-up reel if the film is rough or Jagged stop the machine look for the source of trouble the sprockets carry the film with a smooth continuous motion but at the gate is a set of claws which move in and out up and down to give the film an intermittent movement film is threaded so as to leave small Loops above and below the gate these Loops act as shock absorbers confining the intermittent movement to only a few inches of film a few torn holes like these May travel safely through the sprockets but at the gate the claws failed to drive the film the lower loop tightens and on the screen we have a picture that looks like this without his shock absorber the film is being strained a few torn holes have grown to be a whole series of them it's sometimes possible to reform a loop while the machine is running however it's better to stop the machine immediately there will be less damage and the operator has a chance to check all of the threading one of the most useful parts of a projector is the Little Wheel that lets you turn the Machine by hand it should be used to run through the leader of each film before the showing is begun when the machine is moving as slowly as this it's a simple matter to spot mistakes in threading when a film breaks into it can of course be repaired a splice is really a weld so the trick in making splices is to have the overlapping surfaces absolutely clean roughing them lightly where the razor blade will help and be sure that the cement you use is fresh the projector is clean and well adjusted the film is carefully threaded with proper care a 16 millimeter film will give hundreds of good showings