What is "aperture"

Aperture \Ap"er*ture\ (?; 135), n. [L. apertura, fr. aperire. See Aperient.]

1. The act of opening. [Obs.]

2. An opening; an open space; a gap, cleft, or chasm; a passage perforated; a hole; as, an aperture in a wall.

   An aperture between the mountains.
   --Gilpin.

   The back aperture of the nostrils.
   --Owen.

3. (Opt.) The diameter of the exposed part of the object glass of a telescope or other optical instrument; as, a telescope of four-inch aperture.

   Note: The aperture of microscopes is often expressed in degrees, called also the angular aperture, which signifies the angular breadth of the pencil of light which the instrument transmits from the object or point viewed; as, a microscope of 100[deg] aperture.

early 15c., from Latin apertura "an opening," from apertus, past participle of aperire "to open" (see overt).

n. 1 An opening; an open space; a gap, cleft, or chasm; a passage perforated; a hole; as, an aperture in a wall. 2 (context optics English) Something which restricts the diameter of the light path through one plane in an optical system. 3 (context astronomy photography English) The diameter of the aperture (in the sense above) which restricts the width of the light path through the whole system. For a telescope, this is the diameter of the objective lens. e.g. a telescope may have a 100 cm aperture. 4 (context spaceflight communications English) The (typically) large-diameter antenna used for receiving and transmitting radio frequency energy containing the data used in communication satellites, especially in the geostationary belt. For a comsat, this is typically a large reflective dish antenna; sometimes called an ''array''. 5 (context mathematics rare of a right circular cone English) The maximum angle between the two generatrix.

1. n. a device that controls amount of light admitted

2. a natural opening in something

3. an man-made opening; usually small

The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where the head-foot part of the body of the animal emerges for locomotion, feeding, etc.

The term aperture is used for the main opening in gastropod shells, scaphopod shells, and also for Nautilus and ammonite shells.

The word is not used to describe bivalve shells, where a natural opening between the two shell valves in the closed position is usually called a gape.

Scaphopod shells are tubular, and thus they have two openings: a main anterior aperture and a smaller posterior aperture.

As well as the aperture, some gastropod shells have additional openings in their shells for respiration; this is the case in some Fissurellidae (keyhole limpets) where the central smaller opening at the apex of the shell is called an orifice, and in the Haliotidae (abalones) where the row of respiratory openings in the shell are also called orifices.

The aperture of an optical system is the opening that limits the amount of light that can pass through.

Aperture may also refer to:

In science and technology:

• In anatomy, a number of apertures in the human body:
  • Apertura nasalis posterior
  • Apertura pelvis inferior
  • Apertura pelvis minoris
  • Apertura pelvis superior
  • Apertura thoracis inferior
  • Apertura thoracis superior
  • Lateral aperture (foramen of Luschka), an opening in each lateral extremity of the lateral recess of the fourth ventricle of the human brain
  • Median aperture (foramen of Magendie), which drains cerebrospinal fluid (CSF) from the fourth ventricle into the cisterna magna
• Aperture (antenna), a physical parameter of an antenna
• Aperture (mollusc), the main opening in the shell of a gastropod or scaphopod (mollusc)
• Aperture (botany), a weaker spot in the wall of a pollen grain
• Numerical aperture is a parameter used to describe optical systems
• Aperture (computer memory), a region of the physical address space that opens access to a particular device or memory unit
• Aperture (software), an image organization and editing program for photographers, sold by Apple Inc.

Other uses:

• Aperture (typography), an enclosed loop in a typographical symbol - such as the lower part of the letter 'a'
• Aperture (magazine), a long-running art photography magazine
• Aperture Laboratories, also known only as Aperture, is a fictional organization featured in the Portal video game series

Aperture magazine, based in New York City, is an international quarterly journal specializing in photography. Founded in 1952, Aperture magazine is the flagship publication of Aperture Foundation.

The headquarters of Aperture magazine and the Aperture Foundation and Gallery are at 547 West 27th Street, 4th floor, New York, NY 10001.

Apertures are areas on the walls of a pollen grain, where the wall is thinner and/or softer. For germination it is necessary that the pollen tube can reach out from the inside of the pollen grain and transport the sperm to the egg deep down in the pistil. The apertures are the places where the pollen tube is able to break through the (elsewhere very tough) pollen wall.

The number and configuration of apertures are often very exactly characteristic of different groups of plants. The biggest class of plant species, the Eudicots, usually have three apertures in each pollen grain.

In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are, which is of great importance for the appearance at the image plane. If an aperture is narrow, then highly collimated rays are admitted, resulting in a sharp focus at the image plane. A wide aperture admits uncollimated rays, resulting in a sharp focus only for rays coming from a certain distance. This means that a wide aperture results in an image that is sharp for things at the correct distance. The aperture also determines how many of the incoming rays are actually admitted and thus how much light reaches the image plane (the narrower the aperture, the darker the image for a given exposure time). In the human eye, the pupil is the aperture.

An optical system typically has many openings, or structures that limit the ray bundles (ray bundles are also known as pencils of light). 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. In general, these structures are called stops, and the aperture stop is the stop that primarily determines the ray cone angle and brightness at the image point.

In some contexts, especially in photography and astronomy, aperture refers to the diameter of the aperture stop rather than the physical stop or the opening itself. For example, in a telescope the aperture stop is typically the edges of the objective lens or mirror (or of the mount that holds it). One then speaks of a telescope as having, for example, a 100 centimeter aperture. Note that the aperture stop is not necessarily the smallest stop in the system. Magnification and demagnification by lenses and other elements can cause a relatively large stop to be the aperture stop for the system. In astrophotography the aperture may be given as a linear measure (for example in inches or mm) or as the dimensionless ratio between that measure and the focal length. In other photography it is usually given as a ratio.

Sometimes stops and diaphragms are called apertures, even when they are not the aperture stop of the system.

The word aperture is also used in other contexts to indicate a system which blocks off light outside a certain region. In astronomy for example, a photometric aperture around a star usually corresponds to a circular window around the image of a star within which the light intensity is assumed.

Aperture was a photo editing and management computer program developed by Apple Inc. for the OS X operating system, first released in 2005, and now discontinued from the Mac App Store. The software handles a number of tasks common in post-production work such as importing and organizing image files, applying corrective adjustments, displaying slideshows, and printing photographs.

Features of Aperture include non-destructive editing, organization of photographs by keyword, faces (using face detection and recognition), and places (using GPS metadata embedded in image files), brushes for applying effects (such as dodge and burn, skin smoothing, and polarization), and exporting to several popular websites, including Flickr, Facebook, SmugMug, and Apple's iCloud. The program has been widely reviewed by independent parties.

On June 2, 2014, Apple announced Photos as a replacement for Aperture and iPhoto. Aperture 3.6, a final update adding compatibility with OS X Yosemite, was released on October 16, 2014. Aperture was discontinued and removed from sale on April 8, 2015.

In computing, an aperture is a portion of memory physical address space associated with a particular peripheral device or a memory unit. Apertures may reach external devices such as ROM or RAM chips, or internal memory on the CPU itself.

Typically, a memory device attached to a computer accepts addresses starting at zero, and so a system with more than one such device would have ambiguous addressing. To resolve this, the memory logic will contain several aperture selectors, each containing a range selector and an interface to one of the memory devices. The set of selector address ranges of the apertures are disjoint. When the CPU presents a physical address within the range recognized by an aperture, the aperture unit routes the request (with the address remapped to a zero base) to the attached device. Thus, apertures form a layer of address translation below the level of the usual virtual-to-physical mapping.