We have seen that before the film can be used in the camera it has to be perforated on either side in order that successive areas of film ¾ of an inch deep—the equivalent of a picture—can be seized and brought into position behind the lens. This perforation has become standardised in accordance with what is known as the “Edison Standard Gauge,” which is 64 perforations per foot on either side. This perforation is of an elongated form, measuring about ⅛ of an inch in width by approximately 1/16th of an inch in depth.

The preliminary operation is carried out with a machine, which stamps the holes by means of specially hardened steel punches. Extreme care has to be taken to carry out the task with mathematical accuracy, in order that the film may be used with any type of camera and projector. Without it steadiness of the picture upon the screen is absolutely impossible.

It seems strange that all films should have to be perforated according to the Edison system, when it is remembered that the first commercial cinematographic apparatuses for the projection of pictures upon a screen were made, not by Edison, but by Paul and Lumière, who, one might think, would have established their own gauges. This important point involves an interesting little story.

In the very earliest days of cinematography, when a film of greater width was used than at present, it was advanced by friction. Rollers, or clutches, gripped the edges of the film tightly, and moved it forward the desired extent. But their action was uncertain. Sometimes the rollers became slack and the film slipped, the celluloid ribbon varied in thickness or was a trifle slippery, with the result that the forward movement was irregular, and the pictures did not appear in rhythmic succession. Some were askew, others were overlapped by the preceding or succeeding image, or a wide gap was left between consecutive pictures.

In order to overcome the drawback, attempts were made to devise a system of moving the film forward by the aid of pins engaging with holes in the sides. But the apparatus employed was mechanically defective. The film dragged, and the holes were either torn or became so worn that they did not engage accurately. Square holes were first tried, but the wear and tear set up by the pins or sprocket teeth soon gave them a circular or elongated shape. Then circular perforations were adopted, but they soon became elliptical. The number of perforations per picture was varied also in the hope of securing steadiness of the film both in the camera and more especially in projection, but every effort appeared to refuse to remove the difficulty.

One of the early investigators was discussing the subject one night with Lord Kelvin. The eminent scientist became deeply interested in this trouble with regard to the perforations, and the disadvantages of the respective shapes shown to him. After a few minutes’ reflection, he remarked, “Why not use perforations of triangular form? They will not wear round or square. They will always retain their shape more or less, and at all events will give improved steadiness in running.” The advice of Lord Kelvin was followed, and the triangular holes were found to give the best results achieved up to that time.

Meanwhile the shape of the perforations and the gauge had settled itself in a curious manner. The kinetoscope appeared with small rectangular perforations, numbering four to each picture, on either side of the film. Edison had settled on this plan for his apparatus, finding that it afforded him the best results. The machines were made and despatched to various parts of the world. To maintain the interest in the novelty, a number of films were prepared and sold to various customers possessing the kinetoscope.

When Messrs. Lumière brought out their projecting apparatus, only one brand of film available for demonstration purposes was on the market—that made for the kinetoscope. When Paul first entered the manufacturing field, he, of course, prepared films for use with the kinetoscope of his own manufacture, and he naturally adopted Edison’s gauge. As already narrated, Lumière made an attempt to set up an independent gauge, with one hole each side per picture, but the Edison and Paul films with an identical gauge had become too firmly established, especially as the famous American inventor commanded the situation in the United States. There was no market for either machines or films deviating from Edison’s gauge. Exhibitors who had bought kinetoscopes and films, when they acquired a Lumière projector, demanded that it should be so designed as to use the films which they owned already, and which were highly expensive. When other film-picture manufacturers entered the arena they followed in Edison’s footsteps, because there was no market for their wares if they did otherwise. Consequently the Edison perforation gauge became more and more firmly established as time progressed, until at last it became regarded as the standard. It must be pointed out that this result was largely attributable to Paul, who became the largest manufacturer of kinetoscope films in the world.

Yet it must not be thought that the settlement came about smoothly. There has been a battle of the gauges in the cinematographic as in the railway world. The Edison standard gauge has its admitted drawbacks, the greatest of which is that there are too many holes per picture, which weaken the film and tend to precipitate tearing. Two, or even one, hole per picture on either side would suffice, as demonstration has conclusively proved.

An American rival attempted to swerve from the standard in another direction, using a film 2¾ inches wide—double the width of the kinetoscope film. He eventually abandoned the wide band, partly on economic grounds, as a ribbon half the width produced pictures in every respect equal to those obtained from the wider film. On one or two occasions the gauge has been revised slightly, but the variations merely affected the dimensions of the hole to a microscopic degree. Fundamentally, the gauge as set by Edison for the first commercial apparatus for showing photographs in motion prevails to-day, and is universally accepted.

The film is received from the manufacturers in a plain ribbon, and the perforation has to be done shortly before the film is taken in hand for exposure. The film manufacturers cannot possibly supply it perforated, because the celluloid base undergoes continuous physical change while in storage. Under varying climatic conditions it shrinks and expands to an extent which may not be observable to the eye, but becomes pronounced when the picture is projected upon the screen.

The necessity for mathematical precision in the matter of perforating is somewhat obscure to the uninitiated, but its effects may be demonstrated very easily. Compare the vibrating or oscillating flickering picture of 1896 with that shown upon the screen to-day, in which the effect produced comes very close to that of the camera obscura. If the perforation errs the hundredth part of an inch, steadiness in the picture is forfeited. The films have to be punctured with the same mathematical accuracy that goes to the production of a tiny screw intended for the most delicate piece of mechanism.

This is especially the case in regard to the perforation of the negative film. If this is not absolutely true to gauge, the existing error will be magnified in the passage of the film through the camera; and should the latter be ever so slightly at fault, the defect becomes intensified still more. By the time the picture reaches the projector the infinitesimally small defect in the first instance becomes increased fourfold or even more. The picture will jump and flutter in the most distressing manner, and no matter how dexterous the operator may be, and despite the excellence of his projector, he cannot by any means rectify or mitigate very appreciably defects arising from indifferent perforation.

The contribution of imperfect perforation to unsteadiness in projection was recognised in the earliest days; and great technical skill was devoted to the elaboration of machines to puncture the film with scientific precision. Marvellous appliances have been produced for this purpose; but despite the infinite labour bestowed upon their production the possibility of error is ever present. Still, it has been reduced to infinitesimal proportions, and, given a careful operator, a film can be perforated with the holes varying not a thousandth part of an inch from the gauge.

The very earliest type of perforating machine was known as the “Rotary Perforator,” Paul leading the way in this, as in several other ramifications of the industry. The machine was driven by a mechanism identical with that utilised in the camera and projector; because the film had to be advanced intermittently beneath the punches, which were provided with an oscillating movement. This type of machine is shown in the illustration. Paul’s first appliance has always ranked as more simple, efficient, and reliable than any other.

During recent years the rotary perforator has fallen from favour, on the plea that it soon becomes imperfect in working; but such an accusation cannot fairly be brought against Paul’s machine, since its designer used it continuously for four years, during which time it punched millions of holes, and to-day is as correct in its work as when first used.

It is impossible within the scope of this book to describe all the various types of perforation apparatus now in vogue, more especially as their interest lies mainly in highly technical details. I will content myself with describing three machines which exemplify the three most important methods of perforation.

As this operation has to be carried out in the dark room in the dim light of a ruby lamp, it is imperative that the machines should be of the most simple design and operation, demanding the minimum of labour on the part of the operator.

In the Williamson perforator, four holes on either side of the film are punched at one time, and two films are perforated simultaneously, the sensitised surfaces being face to face. This arrangement obviates the danger of scratching or rubbing the sensitised surface during the operation. One coil of plain film is mounted on the spool A, and another on the lower spool B. The leads from these two spools are taken between the rollers C on to a small platform or guide gate D, where the two superimposed films are brought accurately together to pass under the punches. These are mounted in two rows, the requisite distance apart, in a moving head piece E, which descends at the critical moment, the punches piercing the films cleanly and sharply, the pieces of detached celluloid falling into a receptacle on the floor beneath.

When the head containing the punches rises, the two hooked fingers or claws F engage a hole on either side of the films, and pull them forward ready for the punching of the next four pairs of holes. In addition to carrying four pairs of punches, the head E carries four pairs of projecting pins, set to the same gauge, and before the punch descends these guide pins engage with the four preceding pairs of holes, so that the distance between the sets of four holes on either side is bound to be exactly the same as between any two consecutive holes made simultaneously. The result is that the holes are perforated with absolute mathematical accuracy.

As the film emerges from the perforator proper, it is passed between two guide rollers and a toothed sprocket G, which meshes with the perforations, and thence the lower film passes to the re-winding spool H, and the upper film to the spool J. Between the perforating plate and the respective rollers C and G, small loops will be observed. These are provided for the purpose of obviating any pull upon the film while in the guide gate, and beneath the punches, which might otherwise destroy the alignment and accuracy of the gauge. These loops remain constant, but they can be altered at will while the machine is running without disturbing the actual perforation. The Williamson perforator can be run under power at a relatively high speed, the wheel K being capable of 400 revolutions per minute without impairing the accuracy of the work in the slightest degree.

A different type of machine is represented in the “N.S.” perforator, Fig. 5. In this instance the coil of plain film A is set up in a convenient position away from the machine, but in such a manner that the feed thereto is in an easy curve. The film enters the machine through two roller guides, C and D, to a channel F, and then under the dies in the top plate L. The punctured pieces of film fall away clear of the instrument through the tube N, so that there is no probability of such particles fouling the mechanism and thus possibly upsetting the accurate working of the apparatus. After being perforated the film is moved forward by means of guide pins, and finally issues through a guide B to be re-coiled. This apparatus is very convenient for driving by power, is simple, efficient in its operation, and owing to the solidity of its construction there is little possibility of the precision of the gauge being upset by wear and tear, or by other external influences. The gauge, moreover, can be altered, if desired, to as small a degree as 1/100th of an inch per foot. As the positive film shrinks somewhat after development, it is an advantage to be able to compensate for the contraction when perforating. When the film is dry, although it may have shrunk a trifle, it is found that the gauge is perfectly accurate.

In the Urban-Joy perforator, only a single pair of holes is punched at a time—one on either side of the film. At first sight this method appears somewhat slow, but there is the distinct advantage that the holes are made with incontestable scientific precision, and after all this is the all-important factor. This machine is capable of the very finest adjustment, it being possible to vary the stroke of the punch to the millionth part of an inch. Its simplicity of operation is another distinct point. All strain upon the film is avoided for the simple reason that it is passed through the machine by the pendulum action of the punches. When these are disengaged the film is held in position by a clamp working in opposite step to the action of the punches.

Years of labour have been expended upon the evolution of the perforator. The fruit of these efforts, however, is a material improvement in the steadiness of the picture upon the screen.