American cinematographer (Jan-Dec 1932)

Using 16 mm. Negative Film by DANIEL B. CLARK, A.S.C. FAR too many of us who use I6mm. cameras are prone to overlook the advantages offered by negative film. This is natural enough, since the reversal type of film is more widely distributed, and most of us are in these days inclined to be conservative, and reluctant to spend money experimenting with something unfamiliar as long as we can get by with the equipment or materials to which we are accustomed. Nevertheless, the negative-positive system has much to recommend it; and, in intelligent hands, will give excellent results. The outstanding advantage of the use of negative film is, of course, the fact that, just as in ordinary still photography or 35mm. cinematography, the wear and tear of actual use is taken up by the positive print, leaving the negative in perfect condition for the making of fresh, undamaged duplicate prints at any time. In addition, these prints may be made on any of a large variety of tinted-base positive films, allowing the use of a considerable variety of colors for special effects. Furthermore, although the cost of negative-positive and reversal are approximately the same for the first print, the cost of making duplicate prints with the former is appreciably lower than that of duping reversal film, and the results more satisfactory. The outstanding difficulties connected with the use of negative film are the matter of grain, and the difficulty of finding laboratories whose work is of a quality equal to that of the many reversal-precessing plants of the Eastman and Agfa companies. But both of these difficulties can be surmounted. Since the negative emulsion coated on 1 6mm. film is actually identical with that coated by the same manufacturers on their corresponding 35mm. products ■ — which are used for photographing many professional films, including such fine examples of photography as "Shanghai Express" and "Grand Hotel" — the film in itself cannot be said to be inherently grainy. The responsibility for the apparent increase in grain must be divided between certain factors inherent in I6mm. cinematography and inept handling by the amateur cameraman. The mechanical reasons for the apparently large grain shown in many attempts with 1 6mm. negative are inherent in the I6mm. system. In the first place, the frames are far smaller than on 35mm. film, and — -even with the small screens commonly used in homes — the picture, and with it the images of each minute grain, is subjected to a far greater degree of enlargement than is the case with 35mm. film. But this is not the real seat of the trouble: in viewing a 35mm. picture, the audience is never very close to the screen, while in viewing a 1 6mm. film, the audience is almost on top of it. This proximity makes every detail — especially the objectionable ones — take on an unnatural prominence. In viewing the average 1 6mm. film, the audience is as a rule hardly more than five or six feet away from the screen; in viewing a 35mm. film, the audience is on the average from forty to a hundred feet from the screen. At this distance, normal grain is imperceptible, even on a large screen; but try sitting in the front row of a good-sized theatre: although you will still in all probability be twenty or thirty feet away from the screen, you will become painfully conscious of the grain, and the entire picture will seem like a seething mass of squirmy maggots. But, you will ask, why is it that I see the grain when I use negative, and not when I use reversal film? There are two reasons: one of them has to do with the chemistry of the film; the other with the way you use the film yourself. It is axiomatic that slow emulsions have less grain than fast ones; likewise that positive emulsions have less grain than negative emulsions. Now, reversal film, despite the fact that the nature of the reversal process permits it to have an effective speed identical with that of a corresponding negative emulsion, is basically a positive-type of emulsion, and therefore relatively slow. By the same token, its grain is finer. So much for the inherent grain-characteristics of negative l 6mm. film. Now — what can be done about it? The answer is — understand how it works, and use it properly! Then you will be able to produce pictures in which the grain compares favorably with that of reversal films. Anyone who has studied or read anything at all about photography knows that a film — either still or cine — consists of a celluloid base, upon which is coated an emulsion consisting of microscopic particles of silver-bromide, treated so as to be sensitive to light of different colors, and held in suspension in a thin layer of gelatine. Now, when this film is exposed to light, the action of the light-rays effects some rather intricate chemical and physical changes upon the sensitive silver particles. When the film has been developed by treatment with the proper chemicals, it will be seen that the light has turned these tiny, white particles of silver bromide into black particles of metallic silver. Just how dark these particles are is determined by the strength of the light reaching them. When too much light strikes them, they explode, like a kernel of popcorn, and become tremendously bigger than they would normally be. This is what happens when you overexpose your film. Since these tiny particles are all so greatly over-expanded, it can be seen that they will produce correspondingly large individual images on the finer-grained positive film. It is these expanded images of the "popped" silver particles of the negative emulsion which show up on the screen as grain, and look like little worms crawling over the screen. But since the silver particles only explode this way when exposed to too much light — that is, when the picture is overexposed — the obvious remedy is to underexpose the picture slightly. A great deal of harm has been done by unthinking writers who have said, "When in doubt, with negative film, overexpose a trifle; with reversal film, underexpose a trifle." The fact of the matter is that with either film the best results are secured through a slight underexposure, especially since, with negative, the tone and density of the resultant print can be controlled in the printing. A further aid in overcoming the grain with negative film is the use of the "Non-Halation" or "Creyback" type of film. A number of people have stated that the use of color filters with negative film increases the grain. This is not so; they are mistaking an incidental for the cause of their troubles. As has just been pointed out, it is overexposure that so increases the size of the grain that it becomes objectionable. What has caused these good people trouble when they have attempted to use filters is the fact that they have not calculated correctly the increase in exposure demanded by the filters; they have erred on the side of overexposure, and accordingly burst the silver particles until they became evident on the screen. No, if filters are properly used, they cannot create grain. I recently saw a most interesting reel of filter tests, (Continued on Page 42) 33