Aperture

Uncommon card · No. 108837

In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. The aperture defines a set of rays from each point on an object that will come to a focus in the image plane. This set of rays, sometimes called a bundle of rays or cone of rays, is mathematically a generalized cone (or a bundle of half-lines). An optical system typically has many structures that limit ray bundles. These structures may be the edge of a lens or mirror, or a ring or other fixture that holds an optical element in place or may be a special element such as a diaphragm placed in the optical path to limit the light admitted by the system. These structures are called stops, and the aperture stop is the stop that primarily determines the base of the cone of rays that an optical system accepts (see entrance pupil). As a result, it also determines the ray cone angle and brightness at the image point (see exit...

Read on Wikipedia · Image KoeppiK, CC BY-SA 4.0