Definitions for f-numberˈɛfˌnʌm bər
This page provides all possible meanings and translations of the word f-number
Random House Webster's College Dictionary
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:
The ratio of the focal length of a lens to its diameter; a measure of the light-gathering ability of the lens.
In optics, the f-number of an optical system is the ratio of the lens's focal length to the diameter of the entrance pupil. It is a dimensionless number that is a quantitative measure of lens speed, and an important concept in photography.
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