The Cine Technician (1935-1937)

54 The Journal of the Association of Cine -Technicians Auij-.-Oct., 1936 The Characteristics of Eastman Motion Picture Negative Films By EMERY HUSE, A.S.C., Eastman Kodak Company, Hollywood, California It is generally accepted that photography is the foundation upon which the motion picture industry is built and it is not amiss to state that the negative emulsion is the foundation of photography. Primarily it is because of the importance of and the improvements in negative emulsions that photography has advanced to its present state. A decade ago camera and laboratory men were very httle concerned with the color sensitivity properties of negative motion picture film, and pancliromatic emulsions, while known, were rarely used. In those earlier days orthochromatic negative film was generally used as the medium on which exposures were made. In conjunction with this film use was made of mercury vapor and arc lamps, since these light sources were considered the epitome in the field of studio illuminants. The orthochromatic negative emulsion, because of its blue sensiti\ity, was ideally suited for photography by the radiations emitted from the mercury vapor lamps, since the radiations from this lamp were very pronounced in the same spectral region. The carbon arc also emitted strong bluegreen radiation and it was not uncommon practice to make use of both types of lamps in the illumination of a motion picture set. Since the orthochromatic emulsion was deficient in red sensitivity it mattered not at all that these light sources were deficient in this same spectral region. For exterior photography the orthochromatic film proved very satisfactory since daylight and sunlight likewise emitted considerable blue-green radiation. It would be well at this point to digress and define more adequately the terms orthochromatic and panchromatic. A gelatino-silver bromide emulsion is normally only blue sensitive and unless the use of sensitizing dyes are resorted to, colours other than blue are inadequately reproduced. With the aid of dye sensitizing, emulsions may be rendered sensitive to other portions of the visible spectrum in addition to the normal blue sensitivity of the simple silver bromide emulsion. This silver-bromide emulsion having only blue sensitivity is referred to in photographic terminology as an "ordinary" emulsion. Using this type of emulsion as a basis for dye sensitivity research it was found that certain dyes liinij b'ifui :Eff.:T[»E sir,A:;vt ap*«d . loot **itt 8t^ctref;i-«a ILTUi f«CTl-a£ i»ro I, l.Jj 0 dill > Fig. 1. rendered an emulsion sensitive to the blue-green, green, and yellow portions of the visible spectrum. Emulsions so treated by dyes as to produce this type of sensitivity are known as "orthochromatic" emulsions. The word orthochromatic implies that objects of different colour brightness can be rendered in a truer gray scale than with ordinary emulsions. Further research in the field of dye sensitizing led to the discovery of certain dyes which have the ability to render an emulsion sensitive to the red region of the visible spectrum, this red sensitivity being acquired in addition to the blue, green, and yellow sensitivity of the orthochromatic type. Emulsions containing this additional red sensitivity are referred to as "panchromatic" emulsions, the word panchromatic implying that the emulsion has the ability to record colored objects in terms of grays in their proper brightness relationship. The Eastman Kodak Company first undertook the manufacture of panchromatic emulsion in 1912. These earlier emulsions for the most part were coated on glass plates. As late as 1927 the majority of motion picture productions were made using orthochromatic negative with mercury vapor and arc lamps, but from that date forward there was a steady trend toward the exclusive use of panchromatic films and light sources of the incandescent tungsten lamp type as well as high efficiency carbon arcs. The old type orthochromatic negative emulsion when used with incandescent tungsten lamps, exhibited far less sensitivity than when used with the mercury vapor arc lamps or daylight. It was natural, therefore, that a means be found to make use of this more efficient type of illumination. Since the field of emulsion sensitizing had progressed to the point where \ery acceptable panchromatic film emulsions could be manufactured, it was likewise quite natural that use was made of such emulsions. As was indicated above, the manufacture of panchromatic emulsions in this country began in 1912, but very little panchromatic film had found its way into the motion picture industry prior to 1927. It is difficult to state whether panchromatic film or tungsten lighting equipment first attracted the attention of the photographic world, since for years experimental research had been carried on in both fields, but it is interesting to note that both of them were brought forcibly to the attention of the motion picture industry during the latter part of 1927 and the early part of 1928. The real reason for this was due to the fact that the years of research in the two fields had reached a practical culmination at approximately the same time and since each was partially dependent upon the other, it is not difficult to understand their almost simultaneous introduction to motion picture photography. It is impossible to discuss motion })icture negati\-e emulsions as they are now known without digressing for a moment for a discussion of another development in the field of photography which took place almost immediately after the introduction of panchromatic film and incandescent tungsten illuminations. Reference is made to the fine grain negative developer which was introduced to the trade by the Eastman Kodak Compan} in 1929. The reason that