Photographic Materials

Photographic Materials 

photosensitive materials used in still and motion-picture photography for the production of photographic images, as well as reagents for the chemical processing of such images and supplementary materials.

Photosensitive materials consist of a thin emulsion layer fixed to a backing or a layer without a backing used for the registration of charged high-energy particles. Depending on their chemical composition, such materials are divided into two groups: silver-bearing materials, in which various silver halides and their mixtures (primarily AgBr) serve as the photosensitive component, and silver-free materials, in which compounds of iron and chromium, diazo compounds, and others are used. Silver-free materials are characterized by extremely low photographic sensitivity and are used only for the production of positives, mainly in diazo copying. Depending on the type of backing to which the photosensitive emulsion layer is fixed, photosensitive materials are classified as photographic paper (glossy, matte, and other types), photographic plates (silica or organic glass), and films (cellulose triacetate or various synthetic polymer films).

Photographic reagents are used to convert a latent photographic image into a visible image or to improve the quality of a visible image; photographic developers, fixers, and tanning agents are used for these purposes. Reducers and intensifiers may be used to improve the quality of the image during the processing of photosensitive photographic materials. The application of certain inorganic acids and their salts makes it possible to give the necessary monotone color to positives. Certain operations, such as the intensification and toning of black-and-white images, involve the use of bleaching agents.

Supplementary photographic materials include special light-proof and moistureproof paper for packing photographic materials; adhesives for gluing films and pasting photographic paper onto various materials; and lacquer coatings for protecting positives on ceramics or metals from harmful atmospheric effects.

L. IA. KRAUSH