Movie Makers (Jan-Dec 1938)

335 FITTING FILM TO PURPOSE A discussion of different emulsions and what each of them will accomplish JACKSON M. HACKETT WHEN one has had a little experience in amateur filming, it is not difficult to decide which of the basic types of black and white film he would prefer to use for a particular movie making venture. But, to the man who has just bought his movie camera, the choice of a film may not be so simple. There is the factor of price. Nobody wants to pay more than is necessary for anything, yet it might seem logical to conclude that the best film would be the most expensive one. Generally speaking, the fastest black and white films — those that permit one to make movies under the poorest conditions of lighting — are the most expensive. Increased film speed is an obvious advantage, but, on the other hand, the fastest films are not required for shooting outdoors on a sunny summer afternoon. The value of the extra speed is wasted, and, in fact, the inexperienced cameraman must guard carefully against overexposure when working with this film outdoors. This brings us to a factor more important than that of price — the purpose for which the film is to be used. This factor should be the primary guide in selecting a film, and, after it has been determined, the common sense procedure is to buy the best film one can afford for the purpose. Thus, one can use the large range of films on the market in the most effective way that his pocketbook allows, and, with the slimmest of pocketbooks, it is always possible to make a relatively wise choice. Nor is this consideration of so obvious a method of proceeding as valueless to the experienced amateur movie maker as it might appear. About the technique of such things as movie making, we human beings are inclined to be somewhat superstitious. A movie maker who has been secretly surprised and delighted at the results that he got with one particular type of film is likely to "swear by it" and to use it for any filming purpose, regardless of whether it is suitable or not. So the experienced cameraman, as well as the newest recruit, may be benefited by reviewing the qualities of the basic types of cine films. Of these, the most inexpensive is the ordinary positive type film which is processed by the reversal method. It is frequently termed color blind and may be called "semi chromatic", "semi orthochromatic" or other words or phrases coined to express its inability to record a large section of the color scale. Its low overall sensitivity makes this type of film relatively slow, and it requires from one to two stops more exposure than films of the second basic type. In general, it is suitable only for outdoor shooting in sunlight. The relative speed of this type of film, however, is due somewhat to the particular processing which it receives, and in all cases the exposure directions of the manufacturer must be followed carefully. The color sensitivity of positive type films is limited largely to the blue end of the spectrum, and this film is practically insensitive to all other colors. For this reason, it is unsuited for use with any kind of filter. For instance, a yellow filter, which is commonly used with orthochromatic and panchromatic films, cuts down the amount of blue light, allowing a relatively larger amount of the light of other colors to affect the film. But, in the case of the positive type of film, this filter would simply lessen the amount of the only kind of light to which its emulsion is sensitive. The net result of the filter would be only to reduce the exposure, just as if the diaphragm were closed down somewhat. Filters of other colors, which hold back light that is not blue, also do little else than to cut down the exposure to a marked degree. The slight benefits which might accrue from the use of filters with film of this type are more than offset by the decrease in exposure. The use of filters of any color with this kind of film is not recommended. Since this film is sensitive entirely to blue light and since no filters can be used, it is likely to produce bright white skies on the screen. Fortunately, there is one way in which it is possible to darken the sky under certain lighting conditions. Polarizing material has the property of making skies appear less white on the screen. The effect of darkening is most pronounced if the sunlight is coming from the side, at right angles to the axis of the lens; it is lessened when the sun is either further to the front of the camera or behind it. At its best, the sky effect is very much like that obtainable with panchromatic film and a red filter. A polarizing filter reduces the light to some degree, and it is most suitable for use with positive type emulsions when the sunlight is fairly strong. The same effect may be obtained with a polarizing screen and any other film emulsion. Its special importance in connection with positive type film is that it provides the only means of darkening the sky and eliminating a glaring area of white on the screen. It does not produce a better color rendition in other respects. There has not yet been placed on the market a positive type film that incorporates an anti halation backing to prevent light from spilling over from the white areas in a scene. Because of this fact, in scenes made with this type of film, there is likelihood that a halo will appear around white areas of the picture. For example, a man wearing a white linen suit may appear on the screen to be surrounded by a shimmering band of light. Since this film has a limited range of color sensitivity, nearly all of the colors except white and blue will appear relatively dark on the screen, the reds being reproduced practically as black. This low sensitiv [Continued on page 369]