( Originally Published 1924 )
THE motion-picture, as such, does not exist, but owing to a certain deficiency in our optical organs an illusion of pictures in motion is easily made possible. This deficiency results in a peculiar physiological reaction known as "Persistence of Vision." The sensation which we call "Sight" is the result of light rays of various degrees of size and intensity impinging upon the sensitive retina of the eye. It is believed by modern science that these waves strike the retina with an actual physical impact. However that may be, it is well known that the effect is not instantaneous, but persists for a certain minute period of time. Thus, when we look at a rapidly moving object, we see it indistinctly, though for this to be apparent the motion must be very rapid, as we are accustomed unconsciously to compensate for the deficiencies of our vision and believe that we see many things which we do not see at all. This point will be discussed later, for it is of vital consequence in motion picture drama. Persistence of vision may be easily demonstrated by rapidly whirling a glowing match stick in a darkened room. Instead of seeing a single point of light, traversing a circular path, we see virtually a continuous circle of light. Could we place a tiny light on a disc which could be rotated at a speed of sixteen revolutions or more per second, we should see only a perfect circle of light. This phenomenon was the underlying principle of the phenakistoscope, a toy of a former generation and the forerunner of all modern motion picture apparata. This toy consisted of a hollow drum around the upper rim of which were a number of narrow vertical slots. Inside the lower half of the drum was placed a strip of paper upon which was printed a series of pictures, each differing from the preceding one by a small movement. When the observer whirled this drum and looked through the slots the interruption of vision permitted a glimpse of the pictures only, with a resultant effect which was not unlike that of the modern motion picture, but, of course, far more crude. From such a trifle has grown one of the greatest industries the world has ever known.
Physiologists tell us that the average persistence of vision of the normal adult is approximately one-sixteenth of a second. Therefore, any motion repeated sixteen times per second should present to the eye an illusion of continuous motion. Early experimenters, basing their work on this statement, made and projected pictures at this rate of speed; but, as many of us can remember, the early pictures had a most painful flicker when projected upon the screen. In trying to overcome this obstacle the speed was advanced again and again until pictures were being made and projected at the rate of forty-eight per second, but for some reason the flicker persisted, and the speed was ruinous to the film. After long search, one experimenter tried inserting an extra blade in the shutter which would cut off the light for an instant while the picture remained stationary upon the screen. This blade, the so-called "flicker-blade," proved to be so satisfactory that pictures could be projected as slowly as twelve to the second with far less flicker than had been possible before at much higher speeds. Following this discovery, the original speed of sixteen pictures to the second was once more made standard and so remains to this day, with certain exceptions which shall be explained later.
Owing to the fact that the motion picture does not actually move, but is a rapid succession of slightly different still pictures some mechanism must be obtained whereby the film may be exposed, and a corresponding mechanism by which it may be viewed. The camera mechanism must be such that the exposure may be made, the aperture darkened and the film moved forward one space, or "frame" as it is called, and this complete cycle repeated sixteen times every second. In addition, the film must be retained in the exact focal plane during the exposure, the amount of downward movement of the film must be exact to the thousandth part of an inch and the entire camera must be "rock solid upon some suitable support. Neglect of any one of these points will render a successful motion picture impossible.
Before taking up the specific cameras suited to amateur work, I shall outline the methods by which this movement of the film is accomplished. Every successful motion picture camera has certain boxes or "magazines," which are used to contain the film, protect it from light, yet render it readily accessible for instant use. These magazines must, of course, be light-tight. They also carry the winding spools so that they serve as retort for unexposed film, reels to supply unexposed and to take up exposed film during the operation of exposure and for storage and transportation of exposed film. Some so-called daylight-loading cameras use a reel with solid sides and with the outer end of the film protected by a black paper wrapping, similar to the familiar roll film cartridge; but in whatever form the film carried may be found it may be regarded as a magazine and essential to the successful camera.
Second, there must be some means by which the film may be advanced. This is known as the intermittent movement, and incorporated with it is usually some arrangement of springs, cams or toggle-joints by which the film is firmly held in the focal plane at the instant of exposure. There have been many types of intermittent movements designed and used, only to be discarded. There are three basic designs upon which the great majority of successful movements have been based. The Geneva-star movement is familiar to all mechanics and was, I believe, the first successful motion picture intermittent movement to be used. This is the old Geneva movement which is used in many machines to advance a roller, pulley or gear through a portion of a revolution at equal and regular intervals. Standard motion picture film has four sprocket holes at the side of each frame, while the Geneva sprocket has sixteen teeth. Thus a four point star is used, so that each revolution of the cam advances the sprocket one-fourth revolution and advances the film one frame. This movement is used on at least one camera today and proves quite satisfactory. The greatest drawback is its lack of wearing power, or I should say of its lack of resistance to wear. This necessitates constant readjustment of the movement. Although so rarely used in cameras, this movement is almost universal in projectors, where frequent adjustment is quite practical, and where rough usage must be expected.
Another group of movements may be known as the rocking claw movements. This movement consists of a pair of long arms bearing claws at their extremities which engage the perforations of the film and drag it downward. These arms have imparted to them by means of a crank, a slotted guide or other device, a circular movement in a plane perpendicular to the face of the film. For successful operation it is necessary that this circular path be flattened upon one side so that the movement shall be straight downward. This claw, or pair of claws, works in front of the aperture plate, the claws engaging through slots in that plate. The flattening is obtained by allowing the claws to strike the front of the aperture plate, and as they are mounted on springs, the springs flex and allow the arc to be flattened from the moment of engagement until that of disengagement. Other forms have a "D" shaped slotted guide in which the flat side of the guide secures the straight path of travel. These movements are used in some cheaper grades of news cameras manufactured in this country and are great favorites in English cameras of all grades. The movement is strong and reliable for straight work, but it cannot be relied upon in multiple exposure work where the film must often be re-wound and re-exposed several times. It is also a very noisy movement. It does the work; and usually does it very satisfactorily, but it lacks the quiet operation and minute precision of the highest type of intermittent yet developed, the harmonic cam.
The harmonic cam is a multiple movement, actuated by two distinct cams. One of these cams transmits to the claw carriage an up-and-down movement only, and the other, the so-called drunken screw, moves the claws in and out. Thus the movement of the claw carriage is up-in-down-out-up-in-down-out, etc. This type if intermittent is used in some form in the finest professional cameras manufactured today. It was originated by Pathe Freres and is, of course, incorporated in the Pathe professional cameras. In addition to having this movement the best cameras have the claws machined to fit the perforations exactly, which renders possible multiple exposures without the slightest risk of mis-registration; however, this is a feature which is too costly to manufacture to be incorporated in a camera of the amateur type, nor is it at all necessary for straight work.
Any one of these movements will serve the amateur's purpose as he will seldom desire to make double exposures, and for all straight work, any of the three will be found to be very satisfactory.
When the film has been exposed the work has but begun for the true amateur, just as it has in still photography when the shutter has been released. There follows the development of the negative, the printing and developing of the positive. At present the sixteen millimeter gauge film is all factory finished because the original film is developed and reversed to obtain the final positive, but I venture to predict that appliances for home motion picture finishing will be placed on the market at no far distant date, because the true amateur will not be content to let the other fellow have all of the fun.
The use of standard gauge film involves printing and developing processes just as still photography does, and special equipment is needed for this work. At any rate, some method, reversal or printing must in every instance be used to produce a positive film for projection. Then, when the positive is complete as far as chemical work is concerned, there follows the editing, the insertion of titles and the patching together of related scenes in their proper order, all of which will be treated in their respective places.
So much for generalities; now for particulars. Cinematography is not so much a department of photography as it is a division of that science embracing almost or quite as many departments as does the vast field of still photography. There is undoubtedly no field of still photography, with the possible exception of copying and restoring other photographs, which has not, or will not eventually have its counterpart in the motion field. Of course, we are all familiar with the usual, more or less, dramatic motion pictures of the theatre; but I wonder how many of my readers are familiar with the great number of practical uses to which motion pictures are put at the present time. Probably second in importance is the news-work, which is, by the way, an excellent means by which the amateur may obtain financial returns from his motion work. This work embraces a wide range of topics for the reviews which are not of timely interest, but are analogous to the articles of general interest appearing in monthly journals. This will be taken up in detail later. This branch of cinematography gives employment to hundreds of "free-lances," workers who are not on the staff of any company but who make motion pictures and submit them on approval to the news companies, and who are to be found in all parts of the world. The sun never sets without having shone upon some enterprising cinematography "shooting" some scene or event which later will be flashed upon a thou-sand screens in as many theatres. Then, there is "stop motion" work as applied to puppets, dolls, cartoons and similar work. We have all enjoyed these amusing films without stopping to think of the immense amount of patient and careful work necessary to produce a few hundred feet of film. They are quite within the power of the amateur who has a capacity for endless patience and painstaking care to detail, for such a capacity is of far more value in such work than is an expensive outfit. Strange as it may seem, in this exacting work a camera will serve which might not be entirely satisfactory for ordinary work.
Motion pictures are also being used, to a rapidly increasing extent, in schools and colleges, where kinograms of scientific, historical and literary interest are shown. To the amateur, possibly the only feasible educational field is that of natural science, such as the photography of wild life, birds, animals or reptiles. The field of stop motion may also be used to advantage here in photographing plant life and similar work. Motion pictures are also used by many manufacturers of products too bulky to be carried by salesmen. For example, the manufacturer of heavy machinery can supply his salesmen with a light projector and films which display his product in actual operation, which is obviously of greater value than any still photograph could ever be. This field is also open to the amateur after he has learned the simple laws of straight cinematography and can apply them successfully. Finally, there lies the vast, virgin field of home cinematography, both for individual pleasure and in a manner analogous to home portraiture, and it is to this field that the greater part of this work will apply.
Would you willingly part with that picture of your son, Bob, when he was first learning to walk? You would not take a fortune for it; but try to imagine how much more it would mean to you, could you but sit down of an evening and actually see those faltering steps once more! Or again, how many times have you shown fellow disciples of Ike Walton that photograph in which you are proudly displaying the "big fellow"? What would you give for a strip of film which actually showed the splendid fight he put up?
Cinematography represents a greater advance over still photography than photography did over hand-drawn pictures. It is more nearly recreation than reproduction. Home cinematography is not difficult nor is it very expensive by modern methods; but it supplies us with records which will later be invaluable, to say nothing of the financial returns which are possible to the amateur who cares to go after them.
In the next chapter I shall take up the various cameras now on the market which are suited for amateur work, trying as best I can to point out the advantages and disadvantages of each together with such points of peculiar superiority which render them individually adapted to special lines of work. It is impossible to review every camera made, but in describing those available I shall try to deal with each with absolute fairness, and should any point in my descriptions appear to be misleading I shall be very glad to have such errors called to my attention. I wish to acknowledge my appreciation of the splendid cooperation I have received from the various dealers and manufacturers in supplying me with material with which to work. It is obviously impractical for any one to purchase a sample of each camera on the market, and realizing this, many of these manufacturers and dealers have taken a great deal of trouble to supply me with exact data, photographs and have even made arrangements whereby I could, in many cases, give their cameras a thorough inspection and try-out. I wish to express my feeling of indebtedness to them in this place.