Aperture

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. If an aperture is wide, then uncollimated rays are admitted, resulting in a sharp focus only for rays with a certain focal length. 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 determines the ray cone angle, or equivalently the brightness, at an image point.

Aperture (magazine)

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.

Publication

Aperture is published four times a year, in Spring, Summer, Fall, and Winter. It features photographs by established and emerging photographers, as well as artists experimenting with photo-related media. The magazine also includes writings by critics, scholars, photography practitioners, and others involved in the field of photography.

History

1952–1975

The magazine was founded in 1952 by a consortium of photographers and proponents of photography: Ansel Adams, Melton Ferris, Dorothea Lange, Ernest Louie, Barbara Morgan, Beaumont Newhall, Nancy Newhall, Dody Warren, and Minor White. It was the first journal since Alfred Stieglitz’s Camera Work to explore photography as a fine art. The journal’s mission, as stated in its inaugural issue:

Aperture (mollusc)

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.

In gastropods

In some prosobranch gastropods, the aperture of the shell can be closed, and even completely sealed, with a sort of door or operculum.

Range (statistics)

In arithmetic, the range of a set of data is the difference between the largest and smallest values.

However, in descriptive statistics, this concept of range has a more complex meaning. The range is the size of the smallest interval which contains all the data and provides an indication of statistical dispersion. It is measured in the same units as the data. Since it only depends on two of the observations, it is most useful in representing the dispersion of small data sets.

Independent identically distributed continuous random variables

For n independent and identically distributed continuous random variables X₁, X₂, ..., X_n with cumulative distribution function G(x) and probability density function g(x) the range of the X_i is the range of a sample of size n from a population with distribution function G(x).

Distribution

The range has cumulative distribution function

Gumbel notes that the "beauty of this formula is completely marred by the facts that, in general, we cannot express G(x + t) by G(x), and that the numerical integration is lengthy and tiresome."

Range (music)

In music, the range of a musical instrument is the distance from the lowest to the highest pitch it can play. For a singing voice, the equivalent is vocal range. The range of a musical part is the distance between its lowest and highest note.

The terms sounding range, written range, designated range, duration range and dynamic range have specific meanings.

The sounding range refers to the pitches produced by an instrument, while the written range refers to the compass (span) of notes written in the sheet music, where the part is sometimes transposed for convenience. A piccolo, for example, typically has a sounding range one octave higher than its written range. The designated range is the set of notes the player should or can achieve while playing. All instruments have a designated range, and all pitched instruments have a playing range. Timbre, dynamics, and duration ranges are interrelated and one may achieve registral range at the expense of timbre. The designated range is thus the range in which a player is expected to have comfortable control of all aspects.

Range of a projectile

In physics, assuming a flat Earth with a uniform gravity field, and no air resistance, a projectile launched with specific initial conditions will have a predictable range.

The following applies for ranges which are small compared to the size of the Earth. For longer ranges see sub-orbital spaceflight. The maximum horizontal distance traveled by the projectile

When neglecting air resistance, the range of a projectile will be

If (y₀) is taken to be zero, meaning the object is being launched on flat ground, the range of the projectile will then simplify to

Ideal projectile motion

Ideal projectile motion states that there is no air resistance and no change in gravitational acceleration. This assumption simplifies the mathematics greatly, and is a close approximation of actual projectile motion in cases where the distances travelled are small. Ideal projectile motion is also a good introduction to the topic before adding the complications of air resistance.