OPTICS & OPTICAL PHENOMENA OBSERVATIONAL ASTRONOMY A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site aperture In general, any opening through which light, other forms of electromagnetic radiation, or streams of particles can pass. In photography, the aperture is a hole that allows light to pass through the lens onto the recording surface. A diaphragm aperture works like the iris in the human eye. It can be widened or narrowed automatically or according to a series of manually adjustable values called f-numbers or f-stops. The individual f-numbers represent the focal length of the lens divided by the diameter of the aperture. As the aperture narrows (larger f-number), the depth of field increases. The term aperture is also applied to the diameter of the main mirror in a reflecting telescope, the objective lens in a refracting telescope, or the dish of a radio telescope. The larger the aperture, the greater the ability to collect light and detect faint objects, and the greater the resolving power. In the case of amateur telescopes, a rough guide for estimating the magnification that an aperture can handle well is 2× per mm, or 50× per inch. Related categories    • OPTICS AND OPTICAL PHENOMENA    • OBSERVATIONAL ASTRONOMY Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP