f-number

noun

f-num·​ber ˈef-ˌnəm-bər How to pronounce f-number (audio)
1
: the ratio of the focal length to the aperture in an optical system
2
: a number following the symbol f/ that expresses the effectiveness of the aperture of a camera lens in relation to brightness of image so that the smaller the number the brighter the image and therefore the shorter the exposure required

Examples of f-number in a Sentence

Recent Examples on the Web
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Use a low f-number (f/2.8 or f/4) to allow lots of light into your camera. Jamie Carter, Forbes, 4 Oct. 2024

Word History

Etymology

focal length

First Known Use

1898, in the meaning defined at sense 1

Time Traveler
The first known use of f-number was in 1898

Dictionary Entries Near f-number

Cite this Entry

“F-number.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/f-number. Accessed 21 Nov. 2024.

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