f-number

noun
f-num·​ber | \ ˈef-ˌnəm-bər How to pronounce f-number (audio) \

Definition of f-number

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

First Known Use of f-number

1898, in the meaning defined at sense 1

History and Etymology for f-number

focal length

Keep scrolling for more

Learn More about f-number

Dictionary Entries near f-number

fndg

fndn

fndr

f-number

fo

FO

Fo

Statistics for f-number

Look-up Popularity

Time Traveler for f-number

The first known use of f-number was in 1898

See more words from the same year

More from Merriam-Webster on f-number

Britannica.com: Encyclopedia article about f-number

Comments on f-number

What made you want to look up f-number? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

a haphazard or makeshift solution

Get Word of the Day daily email!

Test Your Vocabulary

Summer 2019 Words of the Day Quiz

  • a-bowl-of-peach-sorbet-with-cut-peaches-next-to-it
  • Which is a synonym of desideratum?
Name That Thing

Test your visual vocabulary with our 10-question challenge!

TAKE THE QUIZ
Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!