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Focal length
Distance behind a lens from the optical centre at which an image is formed of an infinitely distant object.
The distance between the optical centre of a lens and the surface of the film emulsion, tube, or CCD when the lens is set at infinity.
The National Film and Sound Archive of Australia acknowledges Australia’s Aboriginal and Torres Strait Islander peoples as the Traditional Custodians of the land on which we work and live and gives respect to their Elders both past and present.