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Related to f-number: focal length, Numerical aperture


The ratio of the focal length of a lens or lens system to the effective diameter of its aperture. Also called f-stop.

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.



f number

(Photography) 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. See also T-number
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˈɛfˌnʌm bər)

a number corresponding to the ratio of the focal length to the diameter of a lens system, esp. a camera lens. Symbol: f/
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.


n (Phot) → Blende f, → Blendenzahl f
Collins German Dictionary – Complete and Unabridged 7th Edition 2005. © William Collins Sons & Co. Ltd. 1980 © HarperCollins Publishers 1991, 1997, 1999, 2004, 2005, 2007
References in periodicals archive ?
- Fast, high performance Germanium lens with the lowest F-number for a sharp, clear image
Parameter Value Principle Pushbroom Spectral range (nm) 450-850 Spectral sampling (nm) 1.6 Field of view (degrees) 6.57 Instantaneous FOV (mrad) 0.22 F-number 2.5 Pixel size ([micro]m) 7.4 Spatial swath (pixels) 1024 Spectral pixels 512 Slit width ([micro]m) 13.2 TABLE 2: Telescope specifications.
In summary, the basic ingredients to creating starbursts are the following: a) a high f-number (typically between f/11 and f/22); b) some object that blocks the sun (for example) partially; c) some darker object that creates a background for the starbursts to really come out in your photo; and d) a wide-angle lens.
The EF-mount design of Canon's Cinema prime lenses supports communication between camera and lens, enabling features such as display of the f-number in the viewfinder, recording of lens metadata, and Peripheral Illumination Correction.
An exposure value (EV) is to combine a shutter speed and an f-number to be the same exposure [15].
The book includes an extensive list of symbols and an appendix on f-number.
[There is in fact a further complication, as we have to work with inverses: the larger the f-number, the smaller the aperture, but this need not concern us here.] Notice that the shutter speeds also have this same doubling or halving property.
2) Approximately twice as sensitive as a conventional front-illuminated CMOS image sensor by combining back-illuminated CMOS image sensor and bright lens with small f-number. ("IU105F2")