The term fisheye was coined in 1906 by American physicist and inventor Robert W. Wood based on how a fish would see an ultrawide hemispherical view from beneath the water (a phenomenon known as Snell's window).[2][3] Their first practical use was in the 1920s for use in meteorology[4][5] to study cloud formation giving them the name "whole-sky lenses". The angle of view of a fisheye lens is usually between 100 and 180 degrees[1] while the focal lengths depend on the film format they are designed for.