f-number

(efnum′bər)

noun

Photog. a number that represents the relative aperture of a lens, equal to the focal length divided by the effective diameter of the lens aperture: a higher number indicates a smaller opening

See f-number in American Heritage Dictionary 4

noun
The ratio of the focal length of a lens or lens system to the effective diameter of its aperture. Also called f-stop.

Origin:

Origin: f(ocal length)

Origin: + number

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