f-number


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Related to f-number: focal length, Numerical aperture

f-number

, f number
Photog 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
References in periodicals archive ?
A covert lens with an 11-mm FL and a 6-ram aperture has a theoretical f-number of 1.
The most important characteristics of a pinhole lens are its optical speed - the lower the f-number the greater the speed - and its ease of installation and use.
This automatically doubles the f-number of each lens (only one-fourth of the light transmitted).
Generally, the larger the f-number a lens can be set to, the better the picture.
R equals the amount of light that reaches the camera from a known source divided by the amount of light that would have reached the camera through a perfectly transparent lens of the same f-number.
60, shows the relationship between the f-number and the R factor.