The Film Renter and Moving Picture News (Mar-Apr 1923)

86 THE FILM RENTER & MOVING PICTURE NEWS. (Technical Supplement). March 17, 1923. STANDARD DENSITY IN FILM PRINTING—(oninued. Knowing the characteristic curve of the positive film the latitude of exposure for the necessary contrast of each part of the film can then be determined, and those exposures which all parts have in common, prs the latitude of the whole picture. WS ke ¥ Ae That the time of exposure aii lie within these limits is a necessity ; but for the great majority of films thera is a wide range of exposure that satisfies this condition. Are there any other conditions it is desirable to fulfil? SS Physical Contrast. So far the physical or objective contrast alone of the screen picture has been considered. The subjective or apparent contrast is naturally that of most interest. This depends not only upon the physical contrast but also upon the actual quantity of illumination. If this illumination is of too low a value, the physical contrast would not seem as great as it would if more light entered the eye. In other words, unless there is sufficient light on the screen, full benefit. of the physical contrast will not be obtained. Accordingly, since the light on the screen is proportional to the transmission factor of the film, if the source and the optical system are not such as to put spfiicient light on the screen through a film printed to maximum contrast, then a decrease in density will perhaps give a greater apparent contrast, though a smaller physical one. Though too much light decreases the apparent contrast also, this condition is so rare in motion-picture projection as to be of little interest. How Eye-Strain could be Reduced. Eye-strain would probably be reduced to a minimum if the eyes were required to change their adaptation level as little as possible. The eye-strain is often quite noticeable when a change is made from a dark title to a light picture, such as a cartoon, and becomes really painful when in the midst of a dark scene the film breaks. The continual adjustment of eye sensitivity necessary with films as printed at present, would be done away with if every film had the same average transmission. Titles at present transmit far less light than the majority of scenes. They are printed dark to give great contrast between the white letters and the black ground. It is a question as to whether the ease of reading thus obtained is not more than neutralised by the effort to adjust the eyes for the change in illumination. The illusion of darkness and blinding light are desirable at times to obtain ** effects,’’ and the sudden transition to a lower or higher level of illumination could probably be made far more marked if all scenes in which it. was not desired to call attention to the change in illumination, were printed the same average density. CLARKSON Costumes, _ Properties, etc., ‘FILM PRODUCTION S, 41-48 WARDOUR STREET, W. 1. A few of the Films I have Dressed: “THE GLORIOUS ADVENTURE”’ ‘‘ DIANA OF THE OROSSWAYS”’ ‘“‘ JANE SHORE”’ ‘SIXTY YEARS A QUEEN” ‘BATTLE OF WATERLOO ’’ ‘‘GAME OF LIFE”’ ETO., ETO. Still another thing that should be considered in timing the exposure of positive film is that the projection apparatus of theatres is illumination with the average run of film as now printed. Any wide departure of future standard densities from the present average film density may involve a hardship to some theatres, though probably only to those having at present s low screen illumination. Exposures by Definite Rule. These considerations would make it seem advisable to have some universal means of determining the time of exposing positive film that would enable each laboratory to expose its film according to some definite rule of density. If, then, all laboratories adopted the same rule and the same numerical values, each theatre could arrange its projection and general illumination to get the maximum clearness and minimum eyestrain for all pictures, thus contributing materially to the comfort of its audience. To find out, if possible, about what such a rule for printing might be, twenty strips of positive prints from as many different negatives were obtained from a prominent motionpicture laboratory. Each strip consisted of a number of sections, each section having a different time of exposure. The section having what was regarded by the expert judge as the ‘* correct ’? exposure, was marked with a notch in the side of the film. The light passing through these different prints was then measured by allowing the light from a constant source to shine through the film into a photo-electrio cell. A Most Important Factor. The assumption throughout these tests has been that the socalled ‘‘ correct ’’ exposure was, in reality, the most desirable, though it is evident that some, if not all, of the qualities mentioned as theoretically advantageous, are lacking. Certain it is that, by the present method of judging film density, but little account has been taken of the fact that scenes are never run singly, but are links of a long chain; and it is the result of the whole series of prints by which the performance is to be judged—not by the excellence of any single part. The brightness of a picture for best effect, depends largely upon the adaptation level of the eye when the picture is presented, if the scene is of short duration, as so*many now are. For long scenes the eye will adjust itself to any level within wide limits. It is, then, impossible to know how bright a picture will appear unless we know, among other things, how bright was the picture that immediately preceded it on the screen. This brings us to the conclusion that all the present tests, which take account of nothing but the individual film, if not entirely meaningless for short scenes, at least leave out of account one of the most important factors that go to make a proper film density. Unorthodox Perhaps, But All of this sounds most unorthodox, but these are the questions that are coming into men’s minds more and more ag the motion-picture industry grows, for no business can reach the colossal proportions of the motion-picture business and can be kept so constantly before the public, without attracting minds of every kind to it and its problems. You may say,‘‘things cannot be improved enough to pay for the cost of improvement,’’ but this statement will not stand without proof. Real evidence of an experimental nature must be brought forward to show whether improvement can or cannot be made, een