the distance from a focal point of a lens or mirror to the corresponding principal plane. Symbol: f
the distance between an object lens and its corresponding focal plane in a telescope.
- Also called focal distance.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use focal length in a sentence
A super-wide focal length enables a 190-degree field of view, which means the setup can see slightly behind itself.
While the 50mm “wide” focal length does give users more flexibility as a walk-about lens, it also means that users will have to get much closer to their subjects to get the true macro shots.Nikon Z MC 50mm f/2.8 Macro Lens Review: A Solid Introduction to Macro | email@example.com (Unknown) | September 21, 2021 | TechCrunch
It can focus down to 2cm thanks to its super-wide focal length.Let’s watch Apple announce the iPhone 13 and more at its Fall 2021 event | Stan Horaczek | September 14, 2021 | Popular-Science
A fixed lens limits range, sure, but 35-millimeter is my favorite focal length anyway.The Fuji X100V Is My New Favorite Adventure Camera | Jakob Schiller | May 5, 2021 | Outside Online
My two eyes haven't quite the same focal length and this often puts me out of the straight with a column of figures.The Salvaging Of Civilisation | H. G. (Herbert George) Wells
It contains a telescope made by Fitz, whose focal length is seventeen feet, and its object-glass is twelve and a half inches.The College, the Market, and the Court | Caroline H. Dall
The distance from the principal focus to the center of the lens is the focal length or principal focal distance of the lens.Physics | Willis Eugene Tower
The focal length of double convex lenses of crown glass is about the same as the radius of curvature of either surface.Physics | Willis Eugene Tower
I used only the back combination of the lens, which gave a focal length of about twenty-two inches.American Big-Game Hunting | Various
British Dictionary definitions for focal length
the distance from the focal point of a lens or mirror to the reflecting surface of the mirror or the centre point of the lens
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Scientific definitions for focal length
The distance between the optical center of a lens or mirror to its focal point.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Cultural definitions for focal length
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.