Definition: (1) Adjective: ~ lens: type of optical instrument in which focal length or strength of the optic may be varied without substantial change in focus. * Range of focal length is fixed by design e.g. in camera lenses: 17mm to 35mm, 50mm to 300mm. * The effective aperture of the lens may change with change in focal length. Verb: (2) To change the set focal length of a zoom lens. (3) To change the size of an image as it is displayed on screen. * This does not affect the image file itself; only its representation on the monitor.

Related Terms: vari-focal

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