Definition of Focal ratio
1. Noun. The ratio of the focal length to the diameter of a (camera) lens system.
Lexicographical Neighbors of Focal Ratio
Literary usage of Focal ratio
Below you will find example usage of this term as found in modern and/or classical literature:
1. A System of Applied Optics: Being a Complete System of Formulæ of the Second by H. Dennis Taylor (1906)
"A very sli»ht increase in the focal ratio over the above 1'875 : 1 will render the equation insoluble, the nearest approach to freedom from spherical ..."
2. The Encyclopedia Britannica: A Dictionary of Arts, Sciences, Literature and by Hugh Chisholm (1911)
"... but still not quite к> good as the results obtained by using the combination of two convexo-plane lenses of the focal ratio 2 to I. image viewed by the ..."
3. The Astrophysical Journal by American Astronomical Society, University of Chicago (1905)
"... having a focal ratio of less than £. As indicated, the telescope is really triple in character, ..."