ABSTRACT
The more general term glare is preferable, but for photographic systems the term flare is more often used, the two being largely interchangeable. Flare is primarily due to a number of conditions, including the nature of the subject and its surroundings, inter-reflections between surfaces of a lens, reflections and scattering from various mechanical surfaces adjacent to or within the camera and lens, plus artefacts such as dirt or fingermarks on optical surfaces. Camera flare arises from general and local reflecting areas within the camera body or dark chamber, plus the not-inconsiderable reflection from the detector surface itself. Undeveloped photographic film has a reflectance of some 15–40 per cent. Projection flare arises from the usual mechanical and optical causes described but the major cause is the considerable reflection from the screen surface and surrounds. Flare is not considered to be a lens aberration, but it can be more detrimental to lens performance than residual aberrations.
