old U.S. stops vs. stanard f/stopsgreenspun.com : LUSENET : Large format photography : One Thread
I have several old lenses mounted in Kodak ball bearing shutters that date from around 1916. The callibrations are in U.S. stops. How do these relate to modern f/stops?
-- Clark Savage Jr. (email@example.com), May 25, 2001
See this thread (which I found by typeing "US fstops" into a google search):
-- Bill Hahn (firstname.lastname@example.org), May 25, 2001.
Actually, according to Kingslake (History of the Photographic Lens), U.S. stands for "Uniform Scale" and is N*N/16, where N is the f-number.
The beauty of this system is that doubling the U.S. number halves the exposure, instead of the f-number system in which multiplying the f-number by the square root of two halves the exposure.
-- John H. Henderson (email@example.com), May 25, 2001.