Darkening(redirected from darken)
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(or density), the deposition of metallic silver in a photosensitive emulsion in black-and-white photography, or the deposition of dyes in monopacks in color photography, that takes place during development. In photographic materials that do not require development, “direct” darkening occurs immediately after exposure. Darkening that appears upon development of unexposed photosensitive emulsions is called fogging. The quantitative measure of darkening is the optical density of the developed layer or the surface concentration of silver or other light-absorbing substance that produces darkening.