Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
zoom lens (n.)
This term, from motion picture camera and projector jargon first but then adapted to still cameras and binoculars, has now become Standard, at least in its literal technical senses: a zoom lens is one whose focal length is continuously and rapidly adjustable so that it can magnify continuously, enlarging the image without losing focus.
