Definition of f-number in English:

f-number

noun

Photography

The ratio of the focal length of a camera lens to the diameter of the aperture being used for a particular shot (e.g. f8, indicating that the focal length is eight times the diameter).
〔摄〕孔径焦距比，光圈数，f 值
Example sentencesExamples
- All these f-numbers, focal lengths, film speeds and apertures are actually really simple to get to grips with once you understand how they relate to each other and to the finished picture.
- The configuration offers the advantage of high image quality, low distortion, and low f-number, making it ideal for spectral imaging.
- The f-numbers marked on a lens are only truly accurate when the lens is focused at infinity.
- The higher f-numbers mean the diameter of the lens can be smaller, so the lens, using only 20% to 25% as much material, will cost less and weigh less.
- So if you want to have that window frame, the couple, and the envelope all in focus, you need a narrow aperture, and so a large f-number, such as f22.

Origin

Early 20th century: from f (denoting the focal length) and number.

Definition of f-number in US English:

f-number

nounˈef ˌnəmbərˈɛf ˌnəmbər

Photography

The ratio of the focal length of a camera lens to the diameter of the aperture being used for a particular shot (e.g. f8, indicating that the focal length is eight times the diameter).
〔摄〕孔径焦距比，光圈数，f 值
Example sentencesExamples
- All these f-numbers, focal lengths, film speeds and apertures are actually really simple to get to grips with once you understand how they relate to each other and to the finished picture.
- So if you want to have that window frame, the couple, and the envelope all in focus, you need a narrow aperture, and so a large f-number, such as f22.
- The f-numbers marked on a lens are only truly accurate when the lens is focused at infinity.
- The higher f-numbers mean the diameter of the lens can be smaller, so the lens, using only 20% to 25% as much material, will cost less and weigh less.
- The configuration offers the advantage of high image quality, low distortion, and low f-number, making it ideal for spectral imaging.

Origin

Early 20th century: from f (denoting the focal length) and number.

词汇	f-number
释义	Definition of f-number in English: f-number noun Photography The ratio of the focal length of a camera lens to the diameter of the aperture being used for a particular shot (e.g. f8, indicating that the focal length is eight times the diameter). 〔摄〕孔径焦距比，光圈数，f 值 Example sentencesExamples All these f-numbers, focal lengths, film speeds and apertures are actually really simple to get to grips with once you understand how they relate to each other and to the finished picture. The configuration offers the advantage of high image quality, low distortion, and low f-number, making it ideal for spectral imaging. The f-numbers marked on a lens are only truly accurate when the lens is focused at infinity. The higher f-numbers mean the diameter of the lens can be smaller, so the lens, using only 20% to 25% as much material, will cost less and weigh less. So if you want to have that window frame, the couple, and the envelope all in focus, you need a narrow aperture, and so a large f-number, such as f22. Origin Early 20th century: from f (denoting the focal length) and number. Definition of f-number in US English: f-number nounˈef ˌnəmbərˈɛf ˌnəmbər Photography The ratio of the focal length of a camera lens to the diameter of the aperture being used for a particular shot (e.g. f8, indicating that the focal length is eight times the diameter). 〔摄〕孔径焦距比，光圈数，f 值 Example sentencesExamples All these f-numbers, focal lengths, film speeds and apertures are actually really simple to get to grips with once you understand how they relate to each other and to the finished picture. So if you want to have that window frame, the couple, and the envelope all in focus, you need a narrow aperture, and so a large f-number, such as f22. The f-numbers marked on a lens are only truly accurate when the lens is focused at infinity. The higher f-numbers mean the diameter of the lens can be smaller, so the lens, using only 20% to 25% as much material, will cost less and weigh less. The configuration offers the advantage of high image quality, low distortion, and low f-number, making it ideal for spectral imaging. Origin Early 20th century: from f (denoting the focal length) and number.
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