Definitions for f-numberˈɛfˌnʌm bər
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Random House Webster's College Dictionary
f-numberˈɛfˌnʌm bər(n.)
a number corresponding to the ratio of the focal length to the diameter of a lens system, esp. a camera lens.
Category: Optics, Photography
Ref: Symbol: f/ 9
Origin of f-number:
1890–95
Wiktionary
f-number(Noun)
The ratio of the focal length of a lens to its diameter; a measure of the light-gathering ability of the lens.
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