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Petzval Lens
The Petzval objective or Petzval lens, is the first photographic portrait objective lens (160mm focal length) in the history of photography;[1] It was developed by the German-Hungarian mathematics professor Josef Maximilian Petzval
Josef Maximilian Petzval
in 1840 in Vienna,[2] with technical advice provided by Peter Wilhelm Friedrich von Voigtländer (de), the Voigtländer
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Portrait
A portrait is a painting, photograph, sculpture, or other artistic representation of a person, in which the face and its expression is predominant. The intent is to display the likeness, personality, and even the mood of the person. For this reason, in photography a portrait is generally not a snapshot, but a composed image of a person in a still position. A portrait often shows a person looking directly at the painter or photographer, in order to most successfully engage the subject with the viewer.Contents1 History 2 Self-portraiture 3 Official portrait 4 Portrait
Portrait
photography 5 Politics 6 Literature 7 See also 8 References 9 External linksHistory[edit] Main article: Portrait
Portrait
paintingMoche ceramic portrait. Larco Museum
Larco Museum
Collection
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Objective (optics)
In optical engineering, the objective is the optical element that gathers light from the object being observed and focuses the light rays to produce a real image. Objectives can be a single lens or mirror, or combinations of several optical elements. They are used in microscopes, telescopes, cameras, slide projectors, CD players and many other optical instruments. Objectives are also called object lenses, object glasses, or objective glasses.Contents1 Types1.1 Microscope 1.2 Photography and imaging 1.3 Telescope2 See also 3 ReferencesTypes[edit] Microscope[edit] The objective lens of a microscope is the one at the bottom near the sample. At its simplest, it is a very high-powered magnifying glass, with very short focal length. This is brought very close to the specimen being examined so that the light from the specimen comes to a focus inside the microscope tube
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Special
Special
Special
or the specials or variation, may refer to:.mw-parser-output .tocright float:right;clear:right;width:auto;background:none;padding:.5em 0 .8em 1.4em;margin-bottom:.5em .mw-parser-output .tocright-clear-left clear:left .mw-parser-output .tocright-clear-both clear:both .mw-parser-output .tocright-clear-none clear:none Contents1 Policing 2 Literature 3 Film and television 4 Music4.1 Albums 4.2 Songs5 Computing 6 Other uses 7 See alsoPolicing[edit] Specials, Ulster
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International Standard Book Number
The International Standard Book
Book
Number (ISBN) is a numeric commercial book identifier which is intended to be unique.[a][b] Publishers purchase ISBNs from an affiliate of the International ISBN Agency.[1] An ISBN is assigned to each separate edition and variation (except reprintings) of a publication. For example, an e-book, a paperback and a hardcover edition of the same book will each have a different ISBN. The ISBN is ten digits long if assigned before 2007, and thirteen digits long if assigned on or after 1 January 2007. The method of assigning an ISBN is nation-specific and varies between countries, often depending on how large the publishing industry is within a country. The initial ISBN identification format was devised in 1967, based upon the 9-digit Standard Book
Book
Numbering (SBN) created in 1966
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Bokeh
In photography, bokeh (/ˈboʊkeɪ/ BOH-kay — also sometimes pronounced as /ˈboʊkə/ BOH-kə,[1] Japanese: [boke]) is the aesthetic quality of the blur produced in the out-of-focus parts of an image produced by a lens.[2][3][4] Bokeh
Bokeh
has been defined as "the way the lens renders out-of-focus points of light".[5] Differences in lens aberrations and aperture shape cause some lens designs to blur the image in a way that is pleasing to the eye, while others produce blurring that is unpleasant or distracting—"good" and "bad" bokeh, respectively.[6] Bokeh
Bokeh
occurs for parts of the scene that lie outside the depth of field
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Katherine Maher
Katherine Roberts Maher (born April 18, 1983)[1] is the executive director of the Wikimedia Foundation, a position she has held since June 2016.[2] Previously she was chief communications officer.[3] In addition to a background in the field of information and communications technology (ICT), Maher has worked in the non-profit and international sectors focusing on the use of technology to empower human rights and international development.[1]Contents1 Early life and education 2 Career2.1 Wikimedia Foundation3 Honors 4 Leadership 5 Personal life 6 Works and publications 7 References 8 External linksEarly life and education[edit] Maher grew up in Wilton, Connecticut.[1] Maher attended Wilton High School.[4] After high school, in 2003, Maher graduated from the Arabic Language Institute's Arabic Language Intensive Program (ALIN) of The American University in Cairo, which she said was a formative experience, instilling a deep love of the Middle East.[5] Mah
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Ocular Lens
An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks through the device. The objective lens or mirror collects light and brings it to focus creating an image. The eyepiece is placed near the focal point of the objective to magnify this image. The amount of magnification depends on the focal length of the eyepiece. An eyepiece consists of several "lens elements" in a housing, with a "barrel" on one end. The barrel is shaped to fit in a special opening of the instrument to which it is attached. The image can be focused by moving the eyepiece nearer and further from the objective
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Crowdfunding
Crowdfunding
Crowdfunding
is the practice of funding a project or venture by raising many small amounts of money from a large number of people, typically via the Internet.[1] Crowdfunding
Crowdfunding
is a form of crowdsourcing and of alternative finance
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Lomography
Lomography
Lomography
is a commercial trademark of Lomographische AG, which their creators associate to a photographic image style and an analog camera movement and community facilitated by The Lomographic Society International. The Lomographic Society International was founded in 1992 by a group of Viennese students after they discovered the LCA,[1] a camera created by LOMO
LOMO
PLC of Saint Petersburg, Russia. Lomography
Lomography
started as an art movement through which the students put on exhibitions of photos within Vienna; the art movement then developed into a commercial enterprise
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F-number
The f-number of an optical system (such as a camera lens) is the ratio of the system's focal length to the diameter of the entrance pupil.[1] It is a dimensionless number that is a quantitative measure of lens speed, and an important concept in photography
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Vignetting
In photography and optics, vignetting (/vɪnˈjɛtɪŋ/; French: "vignette") is a reduction of an image's brightness or saturation toward the periphery compared to the image center. The word vignette, from the same root as vine, originally referred to a decorative border in a book. Later, the word came to be used for a photographic portrait that is clear at the center and fades off toward the edges. A similar effect is visible in photographs of projected images or videos off a projection screen, resulting in a so-called "hotspot" effect. Vignetting
Vignetting
is often an unintended and undesired effect caused by camera settings or lens limitations. However, it is sometimes deliberately introduced for creative effect, such as to draw attention to the center of the frame
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Astigmatism
Astigmatism
Astigmatism
is a type of refractive error in which the eye does not focus light evenly on the retina.[1] This results in distorted or blurred vision at all distances.[1] Other symptoms can include eyestrain, headaches, and trouble driving at night.[1] If it occurs early in life it can result in amblyopia.[2] The cause of astigmatism is unclear.[3] It is believed to be partly related to genetic factors.[4] The underlying mechanism involves an irregular curvature of the cornea or abnormalities in the lens of the eye.[1][3] Diagnosis is by an eye exam.[1] Three options exist for the
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Coma (optics)
Tilt Spherical aberration Astigmatism Coma Distortion Petzval field curvature Chromatic aberrationComa of a single lensIn optics (especially telescopes), the coma, or comatic aberration, in an optical system refers to aberration inherent to certain optical designs or due to imperfection in the lens or other components that results in off-axis point sources such as stars appearing distorted, appearing to have a tail (coma) like a comet. Specifically, coma is defined as a variation in magnification over the entrance pupil
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Spherical Aberrations
Tilt Spherical aberration Astigmatism Coma Distortion Petzval field curvature Chromatic aberration Spherical aberration
Spherical aberration
is an optical effect observed in an optical device (lens, mirror, etc.) that occurs due to the increased refraction of light rays when they strike a lens or a reflection of light rays when they strike a mirror near its edge, in comparison with those that strike nearer the centre. It signifies a deviation of the device from the norm, i.e., it results in an imperfection of the produced image.On top is a depiction of a perfect lens without spherical aberration: all incoming rays are focused in the focal point.The bottom example depicts a real lens with spherical surfaces, which produces spherical aberration: The different rays do not meet after the lens in one focal point
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