focal length

distance from the center of a lens to the point of focus

The focal length of an optical system is a measure of how strongly it converges (focuses) or diverges (diffuses) light. A system with a shorter focal length has greater optical power than one with a long focal length.
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Noun
1. the distance from a lens to its focus
(synonym) focal distance
(hypernym) distance

See calibrated focal length; equivalent focal length; nominal focal length. 1/3/73

Voir distance focale équivalente; distance focale mesurée; distance focale nominale. 1/3/73

focal length
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