this is sixteen millimeter or something else because it's easily shown on small portable projectors its invention has greatly increased the use and value of motion pictures these days anyone formed by dies suddenly light unfortunately is not the world's strongest material therefore a 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 not see what's inside but it has the disadvantage of being highly inflammable it is almost an explosive there are required to maintain elaborate precautions against fire and to employ a 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 sixteen millimeter film is made of acetate silos acetate film is perfectly safe but it's not as tough as 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 and there get your fingers off the film that's better the manufacturers of sixteen millimeter projectors carefully designed them 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 i 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 rom ten with the film and so there is no friction in spite of the manufactories 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 are for film runs through the gate at the rate of thirty six feet in minute dust and particles of gelatin are accumulating on the surfaces of the plates eventually the hollowed out spaces are filled with and so we have more of those lovely scratches before every real a film the wires operator uses a brush to clean out the gate the operator also while we're talking about scratches here's another way to make them the film is a rom too loosely on the real way think it ought to be tight so we grab the real firmly and pull the film good and hard this is called centering the film and the scratches they look like this it's better to leave the film lo if the film is rough for a jacket stop the machine look for the source of trouble sprockets carry the film with a smooth continuous motion but the gate is a set of claws which move in and out i've been down to give the film an intermittent movement own is threaded so as to leave small loops above and below the gate actor shock absorbers confining the intermittent movement to only a few inches of film a few torn holes like these may travel safer sprockets but at the gate the clock has failed to drive the film the lower lip tightens and on the screen we have a picture that looks like this without it shock absorber the film is being strained a few torn holes have grown to be a whole series of them and sometimes possible to report on the loop while the machine is running however it's better to stop the machine in mediately there will be less damage and the operator has a chance to check all of the threa the project a is plain and well adapted the film is carefully threaded with proper care i think steam millimeter film will give hundreds of good showing