Sara Atkins: Who put the F in F-stop or What the F

What about the origin of the f in f-stop? After a bit of research, we found several intriguing hypotheses about the origin of the term on the easy-to-search photo.net forums. One post references a biography of Ansel Adams, and attributes the italicized f notation to Adams himself, circa 1932.


Sometimes f-stop (or f/stop) and f-number are used interchangeably to indicate the relative size of the lens opening. The f-number series is a geometric progression -- each number in the sequence is multiplied by a factor of 1.4. According to the Lens FAQ onphoto.net, f-stop refers to both maximum lens aperture and to the aperture opening selected in a specific situation for optimal brightness and depth of field. The term "stop" originated in the early days of photography when aperture opening was selected by turning a wheel with different sized holes to let more or less light reach the film.