A variety of black & white emulsion types are available from the film manufacturers. Many are special-pur-pose films designed for scientific or instrumentation use. The cinematographer should be aware of these films and the possibility of using one or more of them if a desired effect cannot be achieved with conventional motion-picture emulsions. For pictorial use, panchromatic emulsions in several speed ranges are available in 35 and 16mm negative and 16mm reversal films. The reproduction of colored objects in terms of shades of gray varies with different types of film.
The cinematographer can control tonal values to get a technically correct rendition of the subject or to exaggerate or suppress the tonal differences for brightness, contrast or other effects by the use of filters. B & W negative films of low or medium speed are most desirable for sharpness and fine grain, and have ample sensitivity for general use. Highspeed film is useful for low "available light" situations or for high-frame-rate photography. Because of the current low frequency of use of black & white as compared to color, it is especially important to establish working exposure indexes relative to the processing laboratory. B & W processing is not as standardized as color processing, differences in chemistry, developing time, and temperature result in changes of contrast as well as exposure index.
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