F-Stops
F-stop is the adjustment to the "Aperture" or diameter of the camera's iris. This is one way to control the amount of light reaching the film. The larger the number, as in. f-stop 22, the smaller the opening. The smaller the opening the greater the depth of field. Each setting up or down allows 1\2 as much light or twice the amount of light. (An f-stop setting of 5.6 allows twice the light of a setting of 8)