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| {{Use dmy dates|date=December 2013}}
| | Let me first you must do introducing me. My name is Edwin Reagan although in order to not historical past of the on my birth cert. Since she was 18 she has been working as a bookkeeper. New Hampshire is where my home is but my [http://Thesaurus.com/browse/partner partner] wants us to cross. To fence is one that I did for a few years. Check out current news for my child website: http://[http://Www.Ehow.com/search.html?s=accessnewyork accessnewyork].se/activity/p/235458/<br><br>my weblog :: [http://accessnewyork.se/activity/p/235458/ bigger penis] |
| {{other uses}}
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| [[File:Apertures.jpg|thumb|A large (1) and a small (2) aperture]]
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| [[File:Aperture in Canon 50mm f1.8 II lens.jpg|thumb|right|Aperture mechanism of Canon 50mm f/1.8 II lens, with 5 blades]]
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| [[File:ApertureDefn1707.png|right|thumb|244px|Definitions of ''Aperture'' in the 1707 ''Glossographia Anglicana Nova''<ref>[[Thomas Blount (Lexicographer)|Thomas Blount]], ''Glossographia Anglicana Nova: Or, A Dictionary, Interpreting Such Hard Words of whatever Language, as are at present used in the English Tongue, with their Etymologies, Definitions, &c. Also, The Terms of Divinity, Law, Physick, Mathematics, History, Agriculture, Logick, Metaphysicks, Grammar, Poetry, Musick, Heraldry, Architecture, Painting, War, and all other Arts and Sciences are herein explain'd, from the best Modern Authors, as, Sir Isaac Newton, Dr. Harris, Dr. Gregory, Mr. Lock, Mr. Evelyn, Mr. Dryden, Mr. Blunt, &c.'', London, 1707.</ref> ]]
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| In [[optics]], an '''aperture''' is a hole or an opening through which [[light]] travels. More specifically, the aperture of an [[optical system]] is the opening that determines the cone angle of a bundle of [[ray (optics)|rays]] that come to a [[focus (optics)|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.<ref>{{cite web|title=What is Aperture?|url=http://wickedsago.blogspot.com/2012/01/what-is-aperture.html|work=Wicked Sago|accessdate=3 March 2013}}</ref> 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 around what the lens is focusing on and blurred otherwise. 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.
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| 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 (optics)|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 (optics)|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.
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| 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.
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| Sometimes stops and diaphragms are called apertures, even when they are not the aperture stop of the system.
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| 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 [[Photometry (astronomy)|photometric]] aperture around a [[star]] usually corresponds to a circular window around the image of a star within which the light intensity is assumed.<ref>Nicholas Eaton, Peter W. Draper & Alasdair Allan, [http://www.starlink.rl.ac.uk/star/docs/sun45.htx/node36.html Techniques of aperture photometry] in PHOTOM -- A Photometry Package, 20 August 2002</ref>
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| ==Application==
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| The aperture stop is an important element in most optical designs. Its most obvious feature is that it limits the amount of light that can reach the image/[[film plane]]. This can be either unavoidable, as in a telescope where one wants to collect as much light as possible; or deliberate, to prevent saturation of a detector or overexposure of film. In both cases, the size of the aperture stop is constrained by things other than the amount of light admitted; however:
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| *The size of the stop is one factor that affects [[depth of field]]. <!-- There is some confusion here. So let's be clear: Long depth of field occurs when the lens opening, and thus the stop, is small. However, a small opening equals a large f-stop number. --> Smaller stops (larger f numbers) produce a longer depth of field, allowing objects at a wide range of distances to all be in focus at the same time.
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| *The stop limits the effect of optical [[Aberration in optical systems|aberrations]]. If the stop is too large, the image will be distorted. More sophisticated optical system designs can mitigate the effect of aberrations, allowing a larger stop and therefore greater light collecting ability.
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| *The stop determines whether the image will be [[vignetting|vignetted]]. Larger stops can cause the intensity reaching the film or detector to fall off toward the edges of the picture, especially when for off-axis points a different stop becomes the aperture stop by virtue of cutting off more light than did the stop that was the aperture stop on the optic axis.
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| *A larger aperture stop requires larger diameter optics, which are heavier and more expensive.
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| In addition to an aperture stop, a photographic lens may have one or more ''field stops'', which limit the system's [[Angle of view|field of view]]. When the field of view is limited by a field stop in the lens (rather than at the film or sensor) [[vignetting]] results; this is only a problem if the resulting field of view is less than was desired.
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| The [[pupil|biological pupil]] of the [[Human eye|eye]] is its aperture in optics nomenclature; the iris is the diaphragm that serves as the aperture stop. Refraction in the [[cornea]] causes the effective aperture (the [[entrance pupil]] in optics parlance) to differ slightly from the physical pupil diameter. The entrance pupil is typically about 4 mm in diameter, although it can range from 2 mm ({{f/|8.3|link=yes}}) in a brightly lit place to 8 mm ({{f/|2.1}}) in the dark.
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| In astronomy, the diameter of the aperture stop (called the ''aperture'') is a critical parameter in the design of a [[telescope]]. Generally, one would want the ''aperture'' to be as large as possible, to collect the maximum amount of light from the distant objects being imaged. The size of the aperture is limited, however, in practice by considerations of cost and weight, as well as prevention of aberrations (as mentioned above).
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| Apertures are also used in laser energy control, focusing, diffractions/patterns, and beam cleaning. Laser applications include spatial filters, Q-switching, high intensity x-ray control.
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| In light microscopy, the word aperture may be used with reference to either the [[Condenser (microscope)|condenser]] (changes angle of light onto specimen field), field iris (changes area of illumination) or possibly objective lens (forms primary image). ''See'' [[Optical microscope]].
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| ==In photography==
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| The aperture stop of a [[photographic lens]] can be adjusted to control the amount of [[light]] reaching the [[Photographic film|film]] or [[image sensor]]. In combination with variation of [[shutter speed]], the aperture size will regulate the film's or image sensor's degree of [[exposure (photography)|exposure]] to light. Typically, a fast shutter will require a larger aperture to ensure sufficient light exposure, and a slow shutter will require a smaller aperture to avoid excessive exposure.
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| [[File:Aperture diagram.svg|right|thumb|350px|Diagram of decreasing aperture sizes (increasing [[f-number]]s) for "full stop" increments (factor of two aperture area per stop)]]
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| A device called a [[diaphragm (optics)|diaphragm]] usually serves as the aperture stop, and controls the aperture. The diaphragm functions much like the [[Iris (anatomy)|iris]] of the [[Human eye|eye]] – it controls the effective [[diameter]] of the lens opening. Reducing the aperture size increases the [[depth of field]], which describes the extent to which subject matter lying closer than or farther from the actual plane of focus appears to be in focus. In general, the smaller the aperture (the larger the number), the greater the distance from the plane of focus the subject matter may be while still appearing in focus.
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| The lens aperture is usually specified as an [[f-number]], the ratio of [[focal length]] to effective aperture diameter. A lens typically has a set of marked "f-stops" that the f-number can be set to. A lower f-number denotes a greater aperture opening which allows more light to reach the film or image sensor. The photography term "one f-stop" refers to a factor of √2 (approx. 1.41) change in f-number, which in turn corresponds to a factor of 2 change in light intensity.
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| [[Aperture priority]] is a semi-automatic shooting mode used in cameras. It allows the photographer to choose an aperture setting and allow the camera to decide the shutter speed and sometimes [[ISO sensitivity]] for the correct exposure. This is sometimes referred to as Aperture Priority Auto Exposure, A mode, Av mode (aperture-value mode), or semi-auto mode.<ref>{{cite web| url=http://elite-cameras.com/articles/aperture-shutter-speed-digital-cameras.php | title=Aperture and shutter speed in digital cameras| work=elite-cameras.com| accessdate=2006-06-20 |archiveurl = http://web.archive.org/web/20060620033626/http://elite-cameras.com/articles/aperture-shutter-speed-digital-cameras.php |archivedate = 2006-06-20}} (original link no longer works, but page was saved by archive.org)</ref>
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| Typical ranges of apertures used in photography are about {{f/}}2.8–{{f/}}22 or {{f/}}2–{{f/}}16,<ref>[http://www.photoxels.com/tutorial_aperture.html What is... Aperture?]<!-- f/2 instead of f/1.8 is clearer and mathematically more accurate as 1 stop faster than f/2.8 --></ref> covering 6 stops, which may be divided into wide, middle, and narrow of 2 stops each, roughly (using round numbers) {{f/}}2–{{f/}}4, {{f/}}4–{{f/}}8, and {{f/}}8–{{f/}}16 or (for a slower lens) {{f/}}2.8–{{f/}}5.6, {{f/}}5.6–{{f/}}11, and {{f/}}11–{{f/}}22. These are not sharp divisions, and ranges for specific lenses vary.
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| ===Maximum and minimum apertures===
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| {{further|Lens speed}}
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| The specifications for a given lens typically include the maximum and minimum aperture sizes, for example, {{f/}}1.4–{{f/}}22. In this case {{f/}}1.4 is the maximum aperture (the widest opening), and {{f/}}22 is the minimum aperture (the smallest opening). The maximum aperture opening tends to be of most interest, and is always included when describing a lens. This value is also known as the [[lens speed|lens "speed"]], because it affects the exposure time. The aperture is proportional to the square root of the light admitted, and thus inversely proportional to the square root of required exposure time, such that an aperture of {{f/}}2 allows for exposure times one quarter that of {{f/}}4.
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| [[File:16 minolta 50mm.jpg|thumb|right|The aperture range of a 50mm Minolta lens, f/1.4–f/16]]
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| Lenses with apertures opening {{f/}}2.8 or wider are referred to as "fast" lenses, although the specific point has changed over time (for example, in the [[1911 Encyclopaedia Britannica]] aperture openings wider than {{f/}}6 were considered fast). The fastest lenses in general production have apertures of {{f/}}1.2 or {{f/}}1.4, with more at {{f/}}1.8 and {{f/}}2.0, and many at {{f/}}2.8 or slower; {{f/}}1.0 is unusual, though sees some use.
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| In exceptional circumstances lenses can have even wider apertures with f-numbers smaller than 1.0; see [[Lens speed#Fast lenses|lens speed: fast lenses]] for a detailed list. For instance, in photography, both the current Leica Noctilux-M 50mm ASPH and a 1960s-era Canon 50mm rangefinder lens have a maximum aperture of {{f/}}0.95. Such lenses tend to be optically exotic and very expensive; at launch, in September 2008, the Leica Noctilux retailed for $11,000.<ref>[http://gizmodo.com/5048115/leicas-11000-noctilux-50mm-f095-lens-is-a-nightvision-owl-eye-for-your-camera Gizmodo: "Leica's $11,000 Noctilux 50mm f/0.95 Lens Is a Nightvision Owl Eye For Your Camera", September 2008]</ref> However, significantly more affordable examples have appeared in recent years, such as the Voigtlander 17.5mm {{f/}}0.95, 25mm {{f/}}0.95 and 42.5mm {{f/}}0.95 manual focus lenses for the [[Micro Four Thirds System]], each of which retails for approximately US$1,000. <ref>[http://www.bhphotovideo.com/c/product/855215-REG/Voigtlander_BA175M_Nokton_17_5mm_f_0_95_Lens.html The Voigtlander 17.5mm f/0.95 at B&H Photo]</ref> <ref>[http://www.bhphotovideo.com/c/product/754598-REG/Voigtlander_BA305A_Nokton_25mm_f_0_95_Lens.html The Voigtlander 25mm f/0.95 at B&H Photo]</ref> <ref>[http://www.bhphotovideo.com/c/product/1000625-REG/voigtlander_ba425m_nokton_42_5mm_f_0_95_micro.html The Voigtlander 42.5mm f/0.95 at B&H Photo]</ref>
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| Professional lenses for some movie cameras have f-numbers as small as {{f/}}0.75. [[Stanley Kubrick]]'s film ''[[Barry Lyndon]]'' has scenes shot with a NASA/Zeiss 50mm f/0.7,<ref>
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| Ed DiGiulio (President, [[Cinema Products Corporation]]). [http://www.visual-memory.co.uk/sk/ac/len/page1.htm "Two Special Lenses for ''Barry Lyndon''"]
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| </ref> the fastest lens in film history. Beyond the expense, these lenses have limited application due to the correspondingly shallower depth of field – the scene must either be shallow, shot from a distance, or will be significantly defocused, though this may be a desired effect.
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| [[Zoom lens]]es typically have a maximum relative aperture (minimum f-number) of {{f/}}2.8 to {{f/}}6.3 through their range. High-end lenses will have a constant aperture, such as {{f/}}2.8 or {{f/}}4, which means that the relative aperture will stay the same throughout the zoom range. A more typical consumer zoom will have a variable maximum relative aperture, since it is harder and more expensive to keep the maximum relative aperture proportional to focal length at long focal lengths; {{f/}}3.5 to {{f/}}5.6 is an example of a common variable aperture range in a consumer zoom lens.
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| By contrast, the minimum aperture does not depend on the focal length – it is limited by how narrowly the aperture closes, not the lens design – and is instead generally chosen based on practicality: very small apertures have lower sharpness due to diffraction, while the added depth of field is not generally useful, and thus there is generally little benefit in using such apertures. Accordingly, DSLR lens typically have minimum aperture of {{f/}}16, {{f/}}22, or {{f/}}32, while [[large format]] may go down to {{f/}}64, as reflected in the name of [[Group f/64]]. Depth of field is a significant concern in [[macro photography]], however, and there one sees smaller apertures. For example, the [[Canon MP-E 65mm f/2.8 1-5x Macro lens|Canon MP-E 65mm]] can have effective aperture (due to magnification) as small as {{f/}}96. The [[Pinhole camera|pinhole]] optic for [[Lensbaby]] creative lenses has an aperture of just {{f/}}177.<ref>{{cite web|url=http://www.lensbaby.com/optics-pinhole.php|title=Pinhole and Zone Plate Photography for SLR Cameras|work=Lensbaby Pinhole optic}}</ref>
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| <gallery>
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| Image:Jonquil flowers at f32.jpg|{{f/}}32 – small aperture and slow shutter
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| Image:Jonquil flowers at f5.jpg|{{f/}}5.6 – large aperture and fast shutter
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| </gallery>
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| ===Aperture area===
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| The amount of light captured by a lens is proportional to the area of the aperture, equal to:
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| :<math>\mathrm{Area} = \pi \left({f \over 2N}\right)^2</math>
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| Where ''f'' is [[focal length]] and ''N'' is the [[f-number]].
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| The focal length value is not required when comparing two lenses of the same focal length; a value of 1 can be used instead, and the other factors can be dropped as well, leaving area proportion to the reciprocal square of the f-number ''N''.
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| If two cameras of different format sizes and focal lengths have the same [[angle of view]], and the same aperture area, they gather the same amount of light from the scene. In that case, the relative focal-plane [[illuminance]], however, would depend only on the f-number ''N'', so it is less in the camera with the larger format, longer focal length, and higher f-number. This assumes both lenses have identical transmissivity.
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| ===Aperture control===
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| Most [[SLR camera]]s provide ''automatic aperture control'', which allows viewing and metering at the lens’s maximum aperture, stops the lens down to the working aperture during exposure, and returns the lens to maximum aperture after exposure.<ref name="Ray2000-136">Sidney F. Ray. The geometry of image formation. In ''The Manual of Photography: Photographic and Digital Imaging'', 9th ed, pp. 136–137. Ed. Ralph E. Jacobson, Sidney F. Ray, Geoffrey G. Atteridge, and Norman R. Axford. Oxford: Focal Press, 2000. ISBN 0-240-51574-9</ref>
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| The first SLR cameras with internal ([[Through-the-lens metering|“through-the-lens” or “TTL”]]) meters (e.g., the [[Pentax Spotmatic]]) required that the lens be stopped down to the working aperture when taking a meter reading. With a small aperture, this darkened the
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| viewfinder, making viewing, focusing, and composition difficult.<ref>{{cite book|last=Shipman|first=Carl|title=SLR Photographers Handbook|year=1977|publisher=HP Books|location=Tucson, AZ|isbn=0-912656-59-X|pages=53}}</ref>
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| Subsequent models soon incorporated mechanical coupling between the lens and the camera body, indicating the working aperture to the camera while allowing the lens to be at its maximum aperture for composition and focusing;<ref name="Ray2000-136"/> this feature became known as automatic aperture control or automatic diaphragm control.
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| For some lenses, including a few long [[Telephoto lens|telephotos]], lenses mounted on [[Bellows (photography)|bellows]], and [[Perspective control lens|perspective-control and tilt/shift]] lenses, the mechanical linkage was impractical,<ref name="Ray2000-136"/> and automatic aperture control was not provided. Many such lenses incorporated a feature known as a "preset" aperture,<ref name="Ray2000-136"/><ref>B. "Moose" Peterson. ''Nikon System Handbook''. New York: Images Press, 1997, pp. 42–43. ISBN 0-929667-03-4</ref> which allows the lens to be set to working aperture and then quickly switched between working aperture and full aperture without looking at the aperture control. Typical operation might be to establish rough composition, set the working aperture for metering, return to full aperture for a final check of focus and composition, and focusing, and finally, return to working aperture just before exposure. Although slightly easier than stopped-down metering, operation is less convenient than automatic operation. Preset aperture controls have taken several forms; the most common has been the use of essentially two lens aperture rings, with one ring setting the aperture and the other serving as a limit stop when switching to working aperture. Examples of lenses with this type of preset aperture control are the Nikon PC Nikkor 28 mm {{f/}}3.5 and the SMC Pentax Shift 6×7 75 mm {{f/}}4.5. The Nikon PC Micro-Nikkor 85 mm {{f/}}2.8D lens incorporates a mechanical pushbutton that sets working aperture when pressed and restores full aperture when pressed a second time.
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| Canon [[Canon EF mount|EF]] lenses, introduced in 1987,<ref>[http://www.canon.com/camera-museum/history/canon_story/f_index.html Canon Camera Museum]. Accessed 12 December 2008.
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| </ref> have electromagnetic diaphragms,<ref>''EF Lens Work III: The Eyes of EOS''. Tokyo: Canon Inc., 2003, pp. 190–191.
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| </ref> eliminating the need for a mechanical linkage between the camera and the lens, and allowing automatic aperture control with the Canon TS-E tilt/shift lenses. Nikon PC-E perspective-control lenses,<ref>[http://www.nikonusa.com/Find-Your-Nikon/Camera-Lenses/Manual/Perspective-Control.page Nikon USA web site]. Accessed 12 December 2008.</ref> introduced in 2008, also have electromagnetic diaphragms.<ref>[http://www.nikonusa.com/Assets/Common-Assets/PDF/PCLenses_Compare2008.pdf Nikon PC-E product comparison brochure] ([[PDF]]). Accessed 12 December 2008.</ref> Automatic aperture control is provided with the newer Nikon digital SLR cameras; with some earlier cameras, the lenses offer preset aperture control by means of a pushbutton that controls the electromagnetic diaphragm.
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| ===Optimal aperture===
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| Optimal aperture depends both on optics (the depth of the scene versus diffraction), and on the performance of the lens.
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| Optically, as a lens is stopped down, the defocus blur at the Depth of Field (DOF) limits decreases but diffraction blur increases. The presence of these two opposing factors implies a point at which the combined blur spot is minimized ([[#CITEREFR Gibson1975|Gibson 1975]], 64); at that point, the <var>f</var>-number is optimal for image sharpness, for this given depth of field<ref>http://www.bobatkins.com/photography/technical/diffraction.html</ref> – a wider aperture (lower ''f''-number) causes more defocus, while a narrower aperture (higher ''f''-number) causes more diffraction.
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| As a matter of performance, lenses often do not perform optimally when fully opened, and thus generally have better sharpness when stopped down some – note that this is sharpness in the plane of [[critical focus]], setting aside issues of depth of field. Beyond a certain point there is no further sharpness benefit to stopping down, and the diffraction begins to become significant. There is accordingly a sweet spot, generally in the {{f/}}4 – {{f/}}8 range, depending on camera, where sharpness is optimal, though some lenses are designed to perform optimally when wide open. How significant this is varies between lenses, and opinions differ on how much practical impact this has.
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| While optimal aperture can be determined mechanically, how much sharpness is ''required'' depends on how the image will be used – if the final image is viewed under normal conditions (e.g., an 8″×10″ image viewed at 10″), it may suffice to determine the <var>f</var>-number using criteria for minimum required sharpness, and there may be no practical benefit from further reducing the size of the blur spot. But this may not be true if the final image is viewed under more demanding conditions, e.g., a very large final image viewed at normal distance, or a portion of an image enlarged to normal size ([[#CITEREFR Hansma1996|Hansma 1996]]). Hansma also suggests that the final-image size may not be known when a photograph is taken, and obtaining the maximum practicable sharpness allows the decision to make a large final image to be made at a later time; see also [[critical sharpness]].
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| ==Equivalent aperture range==
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| In digital photography, the 35mm-equivalent aperture range is sometimes considered to be more important than the actual f-number. Equivalent aperture is the f-number adjusted to correspond to the f-number of the same size absolute aperture diameter on a lens with a [[35mm equivalent focal length]]. Smaller equivalent f-numbers are expected to lead to higher image quality based on more total light from the subject, as well as lead to reduced depth of field. For example, a Sony Cyber-shot DMC-RX10 uses a 1" sensor, 28–200 mm with maximum aperture constant along the zoom range; {{f/}}2.8 has equivalent aperture range {{f/}}7.6, which is a lower equivalent f-number than some other {{f/}}2.8 cameras with smaller sensors.<ref>{{cite web |url=http://www.dpreview.com/previews/sony-cybershot-dsc-rx10 |title=Sony Cyber-shot DSC RX10 First Impressions Review |author=R Butler |accessdate=January 19, 2014}}</ref>
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| ==In scanning or sampling==
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| The terms ''scanning aperture'' and ''sampling aperture'' are often used to refer to the opening through which an image is sampled, or scanned, for example in a [[Drum_scanner#Drum|Drum scanner]], an [[image sensor]], or a television pickup apparatus. The sampling aperture can be a literal optical aperture, that is, a small opening in space, or it can be a time-domain aperture for [[sampling (signal processing)|sampling]] a signal waveform.
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| For example, [[film grain]] is quantified as ''graininess'' via a measurement of film density fluctuations as seen through a 0.048 mm sampling aperture.
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| ==See also==
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| * [[Numerical aperture]]
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| * [[Antenna aperture]]
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| * [[Angular resolution]]
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| * [[Diaphragm (optics)]]
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| * [[Bokeh]]
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| * [[Shallow focus]]
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| * [[Deep focus]]
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| * [[Entrance pupil]]
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| * [[Exit pupil]]
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| * [[Lyot stop]]
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| ==References==
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| * <span id="CITEREFR_Gibson1975">Gibson, H. Lou. 1975. ''Close-Up Photography and Photomacrography''. 2nd combined ed. Kodak Publication No. N-16. Rochester, NY: Eastman Kodak Company</span>, Vol II: Photomacrography. ISBN 0-87985-160-0
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| * <span id="CITEREFR_Hansma1996">Hansma, Paul K. 1996. View Camera Focusing in Practice. ''Photo Techniques'', March/April 1996, 54–57.</span> Available as GIF images on the [http://www.largeformatphotography.info/ Large Format page].
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| <references/>
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| * {{1911}}
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| {{photography subject}}
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| [[Category:Science of photography]]
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| [[Category:Geometrical optics]]
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| [[Category:Physical optics]]
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| [[Category:Observational astronomy]]
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