American cinematographer (Jan-Dec 1932)

32 American Cinematographer • October 1932 EDITOR'S NOTE: Undoubtedly the most important development now taking place in either professional or amateur motion pictures is that of 16mm. sound-on-f ilm. The best brains of the industry are being applied to the problem, which is every day coming nearer to practical solution. As the matter stands now, the gravest question is that of setting definite dimensional standards for the new system: therefore, in this and several succeeding articles, THE AMERICAN CINEMATOGRAPHER is attempting to present in an impartial fashion the viewpoints of the adherents of the various proposed dimensions. THE admittedly attractive features of motion pictures with sound on 16mm. film have heretofore been obscured by some rather difficult technical problems. Obviously, the greatest advantage of 16mm. film lies in its low cost per reel. This holds true in each of the contemplated fields of application, whether industrial, educational, or home entertainment. On the other hand, the factors that permit this low cost, namely, narrow gauge and low film, speed, are the very features that present the most severe technical difficulties in the problem of producing sound from such film. Were it not for these difficulties there would be very little occasion to discuss standards for 16mm. film. Since the 16mm. field must always depend in a large measure upon 35 mm. sources, it is obvious that the most attractive standard would be a simple reduction from standard 35 mm. sound film in the appropriate ratio 1 to 0.4. A discussion of the penalties involved in any departure from this standard is, therefore, pertinent. It is evident that the difficulty of resolving the higher frequencies from any film varies inversely as the film speed. For example, a frequency of 6000 cycles on a 16 mm. film, moving at a speed of 24 frames per second (36 feet per minute), is equivalent to a frequency of 15,000 cycles on a standard 35 mm. sound track. It must be admitted that if such a 16 mm. film were to provide only 40 per cent as good quality as was available in the theatres at the time 16 mm. development began, the results would be highly unsatisfactory. It is not surprising, therefore, that many of the early workers in this field devoted much thought to the possibility of relatively higher film speeds for 16 mm. Among the many suggestions that resulted were several that contemplated film speeds of 72 feet per minute, obtained by projecting alternate frames; and others in which the picture is turned through a right angle and the perforations spaced further apart to obtain speed ranging from 45 to 90 feet per minute. CAM AP GUIDED EDGE PROJ AP Fig. 1. Optical reduction of sound and picture on Standard 16mm film. AMATEUR SECTION Motion Pictures Although each is technically feasible, none of these suggestions are economically practical, most of them being limited by lack of flexibility in production or by excessive film cost. As time passed and as these limitations were more acutely realized, there remained no doubt of the desirability of a simple reduction from existing 35 mm. standards, provided only that the technical difficulties could be overcome and satisfactory results obtained. Upon further reflection there appears to be some hope that satisfactory resolution of high frequencies can be realized from a film traveling at 36 feet per minute. While it is true that 4/10 of the quality even now commercially available in theatres would still be unsatisfactory, it happens that the film itself is by no means the only important factor in present day 35 mm. quality. Recent work has demonstrated that the film is a very much better transfer medium for sound than much of the apparatus necessarily associated with it. On the other hand, the difference in quality between 35 mm. and 16 mm. film rests entirely with the capabilities of the film itself and of the optical elements associated with it, for the reason that microphones, amplifiers, light modulators, light-sensitive cells, and loud speakers all have characteristics entirely independent of the speed with which the film may move whether in recording, printing, or in reproducing sound. In view of these facts, the developmental work here described was begun with the idea of adopting a film standard that would offer the simplest production methods at the lowest possible film cost, quite regardless of the technical difficulties to be overcome. Should it later prove that these difficulties were insurmountable or their solution not commercially feasible, some more favorable form of film layout could then be chosen more intelligently with a more accurate knowledge of the relative merits and penalties involved. This determination led naturally to the adoption of straight optical reduction of the present S. M. P. E. standard 35 mm. sound prints. The results of this developmental work have been very gratifying in that this simple optical reduction of 35 mm. sound prints to 16 mm. sound prints has been justified as an entirely practical and very economical means of producing such film. In making such a film, standard 16 mm. film stock with 2 rows of sprocket perforations is employed, and the sound track occupies a place alongside the picture just as in 35 mm. sound films. The relative dimensions of picture and sound track are practically identical, except that the slightly greater relative width of 16 mm. film as measured between sprocket holes makes it possible to allow proportionately larger unused margins on either side of the sound track, if desired. On the other hand, the Society has already had occasion to consider a film layout in which it is attempted to obtain a wider sound track without widening the film, at the sacrifice of one row of sprocket holes. Of all the suggestions that have been made for 16 mm. sound film layouts, only this and the simple reduced standard have been seriously considered for standardization by the Society; and it seems appropriate, therefore, to make direct comparison of the essential features of each. Fig. 1 shows direct optical reduction of sound and picture on a standard 16 mm. film having the usual two rows of perforations and in all dimensions identical with the film