| 单词 | focal ratio |
| 释义 | focal ratio in British Englishnoun photography another name for f-number f-number in British English or f number noun photography the numerical value of the relative aperture. If the relative aperture is f8, 8 is the f-number and indicates that the focal length of the lens is 8 times the size of the lens aperture See also T-number focal ratio in American Englishnoun Optics & Photography f-number Word origin [1925–30]This word is first recorded in the period 1925–30. Other words that entered Englishat around the same time include: chain reaction, decibel, dropout, off-line, runout |
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