Film, Motion-Picture and Photographic

Film, Motion-Picture and Photographic 

light-sensitive materials that consist of a transparent flexible base coated with a light-sensitive layer. Films are classified as negative, positive, or reversal, depending on their use. Bases that are from 0.11 to 0.14 mm thick are manufactured from cellulose dinitrate, which has great strength but is highly flammable, or from cellulose triacetate, which is not as strong but is nonflammable. Bases that are 0.06 to 0.08 mm thick are made of polyethylene terephthalate, which has great strength and is nonflammable. The base of negative films may be gray or violet; sometimes an antihalo layer is deposited on the film to absorb light and prevent halation, which results from reflected light. The emulsion layer consists of gelatin with uniformly distributed silver halide microcrystals ranging in size from 0.2 to 1.0 microns. The emulsion layer is 15 to 20 microns thick for black-and-white films and up to 35 microns thick for color films.

Films are also classified according to their photographic properties as general- and special-purpose. General-purpose films comprise black-and-white and color films used in artistic and news photography. The films are sensitive to all visible light rays, with light sensitivity ranging from 22 to 350 All-Union State Standard (GOST) units. Higher sensitivity usually means lower contrast and more graininess. The films come on spools that are 16, 35, or 60 mm wide; their lengths vary.

Special-purpose films include the negative, positive, duplicate-negative, and sound-track films used in motion pictures; also in this category are films used in technical photography, such as those employed in reproduction work, aerial photography, roentgenography, and spectrography. For amateur motion pictures, reversal black-and-white and color films are manufactured in 8- and 16-mm widths; the films are wound on spools and are 10 to 15 m long. For professional motion pictures, black-and-white isopanchromatic and color films are manufactured (the latter may be for use in daylight or artificial light); they are 16, 35, and 70 mm wide and up to 300 m long. The films vary in light sensitivity and can be used as general-purpose films. Films for reproduction work are manufactured as flat sheets, whereas those used for microfilming are produced in rolls 35 mm wide. The resolving power of films used in microfilming is usually indicated by each film’s name in terms of lines per m, as in Mikrat-200 or Mikrat-300. Flat X-ray films are used in medicine (type RM) and for structural analysis (type RS). All films are packaged in lightproof materials.

The emulsion layer swells when treated with water or photographic solutions. At temperatures of 37° to 40°C this layer can melt and slip from the base; for this reason the film is processed at lower temperatures.

REFERENCES

Gorokhovskii, Iu. N., and V. P. Baranova. Svoistva cherno-belykh fotograficheskikh plenok. Moscow, 1970.
Kraush, L. Ia. Fotograficheskie materialy. Moscow, 1971.

L. IA. KRAUSH