Plates, Photographic

photosensitive materials in the form of sheets of glass coated with an emulsion of silver-halide microcrystals uniformly distributed in gelatin. The glass must be colorless, smooth, and without visible defects. Photographic plates are made in various standard sizes, ranging from 4.5 × 6 to 50 × 60 cm.

Photographic plates are classified as either general purpose or special purpose, depending on their photographic properties. General-purpose plates are used for artistic and documentary photography and for various scientific and technical purposes. Plates of this type that are manufactured in the USSR have varying degrees of light sensitivity (from 22 to 350 GOST [State Standard] units), color sensitivity (orthochromatic, panchromatic, and isopanchromatic), and contrast (normal, high-contrast, and low-contrast).

Special-purpose plates are intended for scientific and technical use and fall into the following subgroups: (1) diapositive—non-sensitized, low-sensitivity, and high-contrast; (2) reproduction— high-contrast; (3) micro (for photomicrography)—high-definition orthochromatic; (4) astronomical—high-sensitivity and high-contrast; (5) spectral UV—with increased sensitivity to violet and ultraviolet rays; (6) infrachromatic—sensitive to infrared rays; and (7) phototheodolite—orthochromatic, high-contrast, high-definition, and high-resolution.

All photographic plates are packaged in cardboard boxes with opaque packing. General-purpose plates are processed with general-purpose developers, but most special-purpose plates require special developers. A photographic plate’s emulsion swells in water and photographic solutions and can melt at 37° -40°C. For this reason, the use of photographic plates at higher temperatures is not recommended.