The opening that lets light into the camera. The larger the aperture selected the more light there will be to expose the film at any given amount of time. A series of f/numbers is used to denote aperture size, and these are marked on a ring on the lens. These settings, called f-stops, run in a series from largest to smallest: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, and f/22 are the most common.