CHAPTER VI.
THE FILM.
_Film Making and Characteristics._--All film is of celluloid. The commercial film used for the projection of motion pictures comes in long strips, is about one and three-eighths inches wide, and about one two-hundredths of an inch thick. Upon one side of this film is a photographic emulsion of gelatine impregnated with a solution of bromide of silver. This silver is sensitive to the light and has the property of turning black, during the process of developing, in proportion to the quantity of light that has struck the different parts of the emulsion. Wherever the light has been very intense or has been applied for a sufficiently long time, the film, after treatment with a proper developing fluid, becomes very black; where no light has reached it, it remains white; and in the intermediate portions, the shading is in proportion to the light that has reached those parts.
Film that has not been exposed and developed is of a creamy yellowish color and, if immersed in a solution of hyposulphite of soda, will turn perfectly clear and offer no obstruction to the light. If, on the other hand, it is completely exposed and developed, it will become solid black; such black pieces are sometimes used as leaders and tails in connection with motion pictures.
The emulsion on the film melts at a temperature of about 90 degrees Fahrenheit and will then run off the film. It is also soluble in warm water. The celluloid of the film is very inflammable and bursts into flame at a temperature of 284 degrees Fahrenheit. If it is ignited while tightly wound upon a reel, it burns somewhat slowly; if it is ignited in a tank, the beginning of the fire is also slow; but as soon as the air in the tank attains the proper temperature, the whole of the film bursts into flame at once. It acts in this respect very much like gunpowder. In burning, the film gives off a dense brownish mass of poisonous smoke. Film will burn even when it has no access to the air and a film fire cannot be put out by smothering.
Before sending out their films, the manufacturers treat them with glycerine. This is for the purpose of keeping them pliable as long as possible. In time, however, a film dries out and there is then very little that can be done with it. At any rate, whatever is to be done should be done by the exchange, as no operator has facilities for handling it.
Some films are waterproofed and a little water will not damage them much; but other films must be kept dry. If by accident a roll of film should become wet, it can be saved by very quickly unrolling it and spreading it out to dry. If it can be spread out quickly enough, it will not be harmed; but if it is not spread out at once, the emulsion will stick to the celluloid and will come off when the film is finally unwound.
There is also a process of fireproofing film. This must not, however, be too thoroughly relied upon, especially if the film is old. Fireproof film is a valuable aid, but it is best to treat it exactly like other film in respect to the fire hazard.
On account of its inflammable character, film should always be kept in fireproof enclosures.
The film contains sixteen pictures to each foot and for every picture there are four sprocket holes on each side of the film. The size of the aperture plate and also the size of the actual picture on the film is 11/16 inch high by 15/16 inch wide. If the picture on the screen is enlarged to 18 feet 9 inches in width and 13 feet 9 inches high, every part of the picture on the film will appear 57,600 times as large on the screen as it is in the film. In viewing a 1000-foot film, the audience will see 16,000 separate pictures following each other so rapidly that the change from one to the other will be unnoticeable. If a three-blade shutter is used, the beholder will see the light shut off and turned on 48,000 times in the same run of film, but will not be able to notice it if the speed with which it is done is correct.
New film coming directly from the exchange is likely to be too moist and cause trouble from that condition; while old film is likely to be too dry and cause trouble by warping or bending out of shape.
_Patching Film._--All reels of films contain patches and but little trouble will arise from them, provided they are properly made and reasonable care is exercised in watching them. In order to obtain a satisfactory splice, it should not be made more than 3/16 inch long; a greater length than this will reach two sprocket teeth and this is objectionable because the splice stiffens the film and will prevent it from fitting the teeth properly. The splice should be so made that it does not throw the pictures out of frame. If made properly, it will never be noticed in the running picture at all, unless a large quantity of film is cut out. If however, the splice be made over part of a picture--as would be the case if an improper number of holes were cut out--the picture, when projected, would appear out of frame, i.e., the dividing line between two pictures would then appear on the screen and would continue to show until the framing lever had been adjusted to cover the dividing lines again. Care must also be taken that the film is straight after being spliced. If the ends are not fitted squarely to each other, there will be a bend in the film at the point the splice is made; and this may cause trouble.
Many operators have a plate of ground glass fitted into a work bench at the place where splices are to be made and a small lamp under this glass. This is very convenient for, as a rule, the illumination in an operating room is very poor although a good light is necessary to match film properly. If ground glass is used, the rough side must be at the bottom; otherwise it will be difficult to clean off the cement which adheres to the glass.
By making every splice in exactly the same order, the operator will acquire the habit of doing it nicely and quickly. Most splices are made in a hurry (before or after a show) and in this, as well as in all things that must be done hastily and at a moment’s notice, habit and practice are very important. One does not become expert until he has practiced it often enough to be able to do it mechanically.
Proceed as follows and as outlined in Figure 51: Cut exactly along the dividing line of one picture and save this to become the top piece. (The emulsion side of the two sections of film must always be either up or down, and for convenience it is well to form the habit of having them always one way or the other.) Now, with a sharp knife, scrape the celluloid side of this piece until all of the gloss is removed for a width of a little more than 3/16 inch. Do not scrape any more than necessary, but be sure that all dirt and oil are removed. Now take up the other part of the film and cut off the bad portion, leaving a strip a trifle less than 3/16 inch beyond the dividing line. This strip need not be scraped on the back, but all of the emulsion must be scraped from the front side of it. To scrape the front side nicely, lay a short ruler across it to act as a guide for the knife and scrape up to this ruler. Scrape only to the dividing line, but give particular attention to the sprocket holes and the edges, for it is at the edges and sprocket holes that film first begins to work loose and where it is most difficult to secure proper adhesion. Both parts of the film should be so scraped that, when finished, each will furnish half of the dividing line. Now apply a liberal coating of cement to the latter section and carefully lay the first upon it, taking great care that the sprocket holes in the two sections overlap and match perfectly. It is for this matching purpose that the glass in the table (with a small lamp underneath it) is valuable. The sprocket holes must match accurately and the films must line up straight. After the upper film is placed, it must be pressed down for a few seconds until the cement has set. Wipe off all superfluous cement before it has time to set. Be sure that there are four sprocket holes for each picture. Keep a knife on hand and use it for no other purpose. Keep also a suitable stone on which to sharpen this knife, for, unless the knife is very sharp, it will do only poor work and the edge on it will not last long at any rate. Ordinary cement will not hold non-inflammable film, and water-proof film must be more thoroughly scraped than ordinary film. In the bench, provide a recess into which the cement vessel may be set and where it will always remain. Provide also a pair of scissors for cutting the film.
The Edison film mender is shown in Figure 52. This is made with three gates or hinges. Those on the right and left clamp down to hold the film, while the narrower one in the center clamps down on the cemented edge. To mend a film, place one of the pieces to be joined in the mender. Place that part of the gage marked “cut” in position, cutting between first and second perforations above the floor line separating the picture. The remaining piece of film should be placed in the other side of the mender and cut exactly on the line. Set the opposite end of the gage marked “scrape” on the first section; remove the emulsion; cut to the floor line with a sharp pen knife, moistening it so that the emulsion will come off easily. After applying the cement with a brush to the scraped piece, lay the other piece over it in the mender, clamping it down; and leave it for an instant to adhere.