American cinematographer (Jan-Dec 1932)

Super-Sensitive 16 for Exteriors by HAL MOHR. A.S.C. WHEN Super-Sensitive Panchromatic film was first introduced to professional cinematographers, advantage was at first taken only of its obvious superiority for interiors. Since its decidedly greater speed was of relatively little importance for exterior scenes, many cinematographers preferred to use Super-Sensitive only on interior scenes, and continued to use the regular panchromatic film, with which they were naturally more familiar, for exterior work. It is only recently that the majority of professional cinematographers have begun to become aware of the advantage of using SuperSensitive film at all times, whether indoors or out. Amateur cinematographers appear to be following the same course. Super-Sensitive film is, of course, of even greater importance to the amateur worker, with his more limited lighting equipment, than it is to the studio worker. On the other hand, when the amateur attempts to use Super-Sensitive out of doors, without filters, he finds that its increased speed is his undoing, for Super-Sensitive, unfiltered, is so fast that even the smallest stops provided on 16mm. cine lenses generally admit so much light as to overexpose the film. Nevertheless, from my own experience in using Super-Sensitive film in both my professional 35mm. work (I had the good fortune to photograph the first production made on this type of film) and in my personal 16mm. work, I cannot too strongly advise the use of Super-Sensitive film on all occasions. The secret of the successful use of this type of film for exterior cinematography is an understanding of the use of color filters. Naturally, the use of a reasonably heavy filter will increase the exposure to a point where it may be conveniently controlled by the diaphragm adjustments ordinarily provided on amateur apparatus; but this is actually of only secondary importance. The real value of filtering lies in the fact that only through the use of filters can the real benefits of panchromatic film of any type be realized. It will be remembered that the old Orthochromatic film was extremely partial to the blue rays, at the expense of its sensitivity to light of any other color. In Panchromatic and Supersensitive Panchromatic films, this preference to the blue has continued, though with increasing sensitivity to the red, yellow, green and other colors. In order to lessen this preference for the blue components of a scene, various filters are used which retard the passage of the blue rays to a certain extent, and permit the weaker red, yellow, and green rays to do their work. Since the filters remove a part of the light without adding anything to take its place, the exposure must be lengthened in the exact proportion that the filter retards the blue rays. This is true of all types of film; but the exact degree in which the exposure must be lengthened depends entirely upon the speed and color-sensitivity of the film used. Clearly, if a filter which cuts out, say 50% of the blue light, is used on Ortho film, which is only very slightly sensitive to the other colors, the exposure must be increased considerably to otain a satisfactory exposure; the same filter, used with regular Panchromatic film, which is moderately sensitive to these other colors, will require a smaller increase in exposure; while the same filter used with Super-Sensitive Panchromatic film, which is not only faster overall, but highly sensitive to red, yellow and green, will in this case require only a very small increase in exposure. This change in color-sensitivity naturally makes the same filter give different effects on different types of film. Therefore, as many professional cinematographers have found out, one may know a great deal about the effects of filters on regular Panchromatic film, and yet have a great deal to learn about the use of the same filters with Super-Sensitive film. The results, however, are eminently worth the additional trouble of learning. The increased speed naturally decreases the added exposure necessary with any given filter. If, for instance, we have a filter which, when used with regular Panchromatic film, requires an increase of 3 times, the same filter, used with SuperSensitive film, will require an increase of only 1 Vz times in the exposure. This is obviously an advantage to the owners of cameras equipped with slower lenses; with an f:3.5 lens, for instance, a 12-times filter on regular Panchromatic film increases the exposure beyond the capabilities of the lens, while the same filter, used with Super-Sensitive film, requiring an increase of only 6 times, is quite practical. The same is true of many of the extremely fast lenses, which tend to lose both depth of focus and sharpness when opened to their extreme apertures. But this is not all. The differences in color sensitivity between the regular and Super-Sensitive Panchromatic emulsions is such that a filter will produce entirely different results when used on the two films. In the main, to produce a given result on the faster film one must use a considerably heavier filter than he would use to produce the same result on regular Pan. To produce, for instance, the correction given on regular Pan by the orange-yellow "C" filter, the user of Super-Sensitive would have to use a decidedly heavier red filter — either an "A" or an "F". On the other hand, the sensitivity of the faster film is such that the film already embodies the correction given by the "K-2" filter; that is, Super-Sensitive film will give, without the use of any filter, the same result that ordinary Panchromatic will require a "K-2" filter to obtain. The choice of film really therefore depends upon the sort of picture you want to produce. If you want to have a picture that is obviously filtered in appearance, use the regular film. If you want a picture which is predominantly natural, and yet embodies the desired correction (without exaggeration), use the Super-Sensitive type. The most useful filters for Super-Sensitive film are the "C", the "23-A", the "29-F", the "B" and — if one wants to make night-effects by daylight, the "72-Camma." The recently-introduced "X" filters, though frequently used by amateurs, are really of little use, as they were made especially for a certain still portrait-film, and are not intended for motion picture use, either professional or amateur. The "G" filter is by far the best for all-around use where a moderate correction is desired. It requires an increase of slightly less than a stop and a half in exposure. For greater correction, the "23-A" is unexcelled, for although it is a red filter, it does not make people's faces photograph unpleasantly light, and it gives a very pleasing correction, with fine contrast, and cuts through ordinary haze like a knife. When working in unfavorably flat lights, the "F" filter is a tremendous aid, for it increases the visual contrast, and literally puts contrast into scenes where otherwise there could be none. It requires an increase of six times in exposure — approximately three stops. The "B" filter, which is green, does just the reverse, and softens unpleasantly harsh contrasts. Like the "23-A", it requires an increase in exposure of a stop and a half. The "72" or "Gamma" filter is an extremely heavy one: when used to secure normal scenes with its extreme (Continued on Page 37) 32