Motion Picture News (Nov-Dec 1925)

2706 Motion Picture News Projection Optics , Eleetr ieity,Prdetical Ideas ^ adhtie Inquiries and Comments Standardized Screen Brightness PART II XCESSIVE illumination of the screen in the general run of Motion Picture Theatres, which has at last stirred up activity directed toward the end of arriving at some kind of standardization of screen brightness, is costing the motion picture industry thousands of dollars annually. This evil plays no favorites and strikes producers, exhibitors and theatre patrons alike. "With the first two groups it is a matter of financial loss entailed by waste and in the last it involves acute discomfort and the likelihood of serious impairment to vision. In extreme cases loss of patronage with its consequent effects down along the line, is the ultimate outcome. Small wonder, then, that responsible bodies like the Society of Motion Picture Engineers and large producing companies alive to the dangers underlying this pernicious practice are considering measures to assist in eliminating it. It is a good sized job, that is true. A tremendous amount of educational work must be done before the average exhibitor can be made to see the advantages of using a safe and sane intensity of screen illumination. At this point, however, we are a little ahead of our story. Aside from the necessity of selling exhibitors and projectionists alike on the idea there remains to be evolve 1 a practical method whereby a practical standard for screen brightness can be established. The problem has many angles. Any talk of a standard screen brightness immediately opens up the question of a standard film density. It is useless to talk standardization when the density of film at present released by exchanges varies all over the lot and then back again. Steps have been taken by certain producers to use a constant standard intensity of light for printing purposes. Some progress has been made along these lines already but the difficulty lies in convincing a sufficiently large percentage of them to follow the practice of a constant, well regulated, printing intensity. Passing the Buck The usual argument of a certain class of producers, when approached with this end in mind, is that no good can result from regulating the density of film as long as the conditions of projection vary as greatly as they do. The film which is projected with an " intensity of four foot-candles in one theatre may easily encounter 10 to 12 footcandles in the next. It is obvious that in one of these two theatres the picture will be either brilliantly illuminated or greatly under-illuminated. The usual arguments such as condition and type of screen surface and conditions of local surroundings are also advanced to support the main one of widely varying pro jection intensities encountered. There is a certain amount of logic in this line of reasoning. It is true as far as it goes. The point that is overlooked is this. The producing companies, in a way, represent the source of this evil. Widely varying film densities practically render it necessary for the exhibitor to overpower his projectors so as to be prepared to meet all conditions of film and at the the same time provide him with a powerful argument wherewith to resist efforts to have him to change. That argument should be taken away from him. Standard film density comes first. After that we can talk standard screen brightness. Exhibitor's Loss The exhibitor's interest in this matter lies in effecting economies of operation in addition to being able to present pictures so as to bring out fine effects on which the producer has expended much time and money to incorporate in the scenes. Let us consider the first item — that of lower operating costs — since that is easier to calculate. In order to be conservative let us place the number of theatres in this country at 14,000. All of these theatres certainly do not operate on a ten hour daily schedule for six days per week but it would probably be safe to say that the equivalent of 10,000 theatres in this country average a total of sixty projection hours per week. In some localities theatres operate longer than this but in many others the period is much less. A fair figure, however, would seem to be that given above. The total number of hours operation per year, would therefore be about 3,000 for each theatre, and for 10,000 theatres the total for the country would be 30,000,000. No projection device is 100 per cent efficient and the projectionist does not live who can attain the same degree of efficiency in his work. Some loss is therefore, inevitable. Suppose every one of these theatres wasted 100 watts of electrical energy during proieetion of the picture. The total waste for the country would be 3,000,000 kilowatt hours annually and at an average power rate of five cents per kw. hr. this would represent a yearly loss of $150,000. Now a 100 watt loss in the case of 25 ampere reflector are would mean an operating efficiency of about 95 per cent. Does it seem probable that projectionists in this country — or anv other for that matter are that efficient. If personal observation in a large number of theatres counts for anything we should say that such a figure is indeed highly improbable. It can be safely said that the average projectionist will not deliver more than 75 i er cent of the full value of electrical energy on the screen in the form of light. We know many who are not doing that good. Somewhere we once saw figures which purported to show that the average size of arc used for projection purposes was of 50 amperes capacity using direct current. We have no idea as to whether or not this figure is correct and for that matter, we doubt whether anyone else has. It seems, however, like a fair average for all the theatres. A 50 ampere D. C. arc supplied by a motor-generator set would require a total power consumption of about 4,000 watts. If 25 per cent of this energy is lost in projecting the picture to the screen the total loss for the country would be 30,000,000 kw. hr. at a cost of $1,500,000. Surely no small item! There is a strong possibility that the actual loss due to inefficient operation even exceeds this figure. It is claimed for both the reflector arc and Mazda lamp that savings of from 25 to 75 per cent over the old form of are can be obtained. Yet with either of these devices a power loss of from 250 to 400 watts is involved due to faulty operation. If every theatre in the country was equipped with one or the other of these two most efficient projection means, a total loss of from $450,000 to $600,000 would probably be involved. It is our guess that in excess of $2,000,000 is annually wasted due to inefficient devices and methods of projection. All that has been said so far has to do with natural losses which can hardly be avoided unless expert projectionists be employed in every theatre. In addition to the large waste which occurs due to natural factors of operation, the exhibitors are voluntarily saddling themselves with the burden of a far greater waste by using power in excess of that required for same projection results and by accepting, or promoting, such designs of theatres that the most powei-ful projection devices are required to supply a picture no brighter than could be provided by a more economical projection lamp used at a shorter distance. It is unusually the case, when improvements in any device are wrought, to use such improvements for securing better operating results rather than lower costs. This has occurred time and again in the lighting industry where the improvements in the way of increased efficiency in incandescent lamps has invariably been applied to secure higher intensities of illumination, rather than a lower cost of operation. So also with the projection field. Coupled with this fact we have the natural proclivity of the exhibitor to over exert himself in securing a bright picture, no matter what the projection device be. It would be useless to attempt even a wild guess as to the power waste which yearly occurs due to "overshooting" but it is intended in future articles to outline a method for arriving at a desirable value of screen brightness.