equivalent focal length
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equivalent focal length
[i′kwiv·ə·lənt ′fō·kəl ‚leŋkth] (optics)
The focal length of a thin lens which forms images that most nearly duplicate those of a given compound lens, thick lens, or system of lenses.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.