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Related to indirect illumination: direct illumination
Battlefield illumination provided by employing searchlight or pyrotechnic illuminants using diffusion or reflection. a. Illumination by diffusion: Illumination of an area beneath and to the flanks of a slightly elevated searchlight or of pyrotechnic illuminants, by the light scattered from atmospheric particles. b. Illumination by reflection: Illumination of an area by reflecting light from low cloud. Either or both of these effects are present when a searchlight is used in defilade or with its beam spread to maximum width.
Dictionary of Military and Associated Terms. US Department of Defense 2005.