The air spaces between the glass lens elements making up a photographic lens can be thought of as lenses made of glass having the same index of refraction as air (1.0). An air space designed from the beginning with this concept in mind is called an air lens. Since the refraction of an air lens is opposite that of a glass lens, a convex shape acts as a concave lens and a concave shape acts as a convex lens. This principle was first propounded in 1898 by a man named Emil von Hoegh working for the German company Goerz.canonglossaryeu
A relatively large area of white space in a layout.
bubbles of air clinging to the emulsion surface during processing.
method of retouching b&w or color photographs where dye is sprayed, under pressure, on to selected areas of the negative or print.