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A camera lens (also known as photographic lens or photographic objective) is an
optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities ...

optical
lens A lens is a transmissive optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, s ...

lens
or assembly of lenses used in conjunction with a
camera A camera is an optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and t ...

camera
body and mechanism to make images of objects either on
photographic film Photographic film is a strip or sheet of transparent coated on one side with a containing microscopically small light-sensitive crystals. The sizes and other characteristics of the crystals determine the sensitivity, contrast, and of the ...
or on other media capable of storing an image chemically or electronically. There is no major difference in principle between a lens used for a
still camera A camera is an optical Optics is the branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, i ...
, a
video camera A video camera is a camera A camera is an optical Optics is the branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural ...

video camera
, a
telescope A telescope is an using lenses, curved mirrors, or a combination of both to observe distant objects, or various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. The first known ...

telescope
, a
microscope A microscope (from grc, μικρός ''mikrós'' 'small' and ''skopeîn'' 'to look (at); examine, inspect') is a used to examine objects that are too small to be seen by the . is the of investigating small objects and structures using a ...

microscope
, or other apparatus, but the details of design and construction are different. A lens might be permanently fixed to a camera, or it might be interchangeable with lenses of different
focal length The focal length of an optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...

focal length
s,
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 ray (optics), rays that come to a focus (optics), focus ...

aperture
s, and other properties. While in principle a simple convex lens will suffice, in practice a compound lens made up of a number of optical
lens elements
lens elements
is required to correct (as much as possible) the many
optical aberration Optics is the branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion a ...
s that arise. Some aberrations will be present in any lens system. It is the job of the lens designer to balance these and produce a design that is suitable for photographic use and possibly mass production.


Theory of operation

Typical
rectilinear lens In photography Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. I ...
es can be thought of as "improved"
pinhole "lenses"
pinhole
. As shown, a pinhole "lens" is simply a small aperture that blocks most rays of light, ideally selecting one ray to the object for each point on the image sensor. Pinhole lenses have a few severe limitations: * A pinhole camera with a large
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 ray (optics), rays that come to a focus (optics), focus ...

aperture
is blurry because each pixel is essentially the shadow of the aperture stop, so its size is no smaller than the size of the aperture (third image). Here a pixel is the area of the detector exposed to light from a point on the object. * Making the pinhole smaller improves resolution (up to a limit), but reduces the amount of light captured. * At a certain point, shrinking the hole does not improve the resolution because of the
diffraction limit , who approximated the diffraction limit of a microscope as d=\frac, where ''d'' is the resolvable feature size, ''λ'' is the wavelength of light, ''n'' is the index of refraction of the medium being imaged in, and ''θ'' (depicted as ''α'' in the ...
. Beyond this limit, making the hole smaller makes the image blurrier as well as darker. Practical lenses can be thought of as an answer to the question: "how can a pinhole lens be modified to admit more light and give a smaller spot size?". A first step is to put a simple convex lens at the pinhole with a focal length equal to the distance to the film plane (assuming the camera will take pictures of distant objects). This allows the pinhole to be opened up significantly (fourth image) because a thin convex lens bends light rays in proportion to their distance to the axis of the lens, with rays striking the center of the lens passing straight through. The geometry is almost the same as with a simple pinhole lens, but rather than being illuminated by single rays of light, each image point is illuminated by a focused "pencil" of light rays. From the front of the camera, the small hole (the aperture), would be seen. The
virtual image Image: Virtual image.svg, Top: The formation of a virtual image using a Lens (optics)#Types of lenses, diverging lens. Bottom: The formation of a virtual image using a convex mirror. In both diagrams, ''f''  is the focal point, ''O''  is t ...

virtual image
of the aperture as seen from the world is known as the lens's
entrance pupil In an optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the ...
; ideally, all rays of light leaving a point on the object that enter the entrance pupil will be focused to the same point on the image sensor/film (provided the object point is in the field of view). If one were inside the camera, one would see the lens acting as a
projector image:IFA 2012 IMG 5767.JPG, 200px, Acer inc., Acer projector, 2012 A projector or image projector is an optical device that projects an image (or moving images) onto a surface, commonly a projection screen. Most projectors create an image by shin ...
. The virtual image of the aperture from inside the camera is the lens's
exit pupil In optics Optics is the branch of that studies the behaviour and properties of , including its interactions with and the construction of that use or it. Optics usually describes the behaviour of , , and light. Because light is an , other ...

exit pupil
. In this simple case, the aperture, entrance pupil, and exit pupil are all in the same place because the only optical element is in the plane of the aperture, but in general these three will be in different places. Practical photographic lenses include more lens elements. The additional elements allow lens designers to reduce various aberrations, but the principle of operation remains the same:
pencils of rays
pencils of rays
are collected at the entrance pupil and focused down from the exit pupil onto the image plane.


Construction

A camera lens may be made from a number of elements: from one, as in the Box Brownie's meniscus lens, to over 20 in the more complex zooms. These elements may themselves comprise a group of lenses cemented together. The front element is critical to the performance of the whole assembly. In all modern lenses the surface is coated to reduce abrasion,
flare A flare, also sometimes called a fusée, is a type of pyrotechnic that produces a bright light or intense heat without an explosion An explosion is a rapid expansion in volume associated with an extremely vigorous outward release of en ...

flare
, and surface reflectance, and to adjust color balance. To minimize aberration, the curvature is usually set so that the angle of incidence and the
angle of refraction of light at the interface between two media of different refractive indices, with n2 > n1. Since the velocity is lower in the second medium (v2 < v1), the angle of refraction θ2 is less than the angle of incidence θ1< ...
are equal. In a prime lens this is easy, but in a zoom there is always a compromise. The lens usually is focused by adjusting the distance from the lens assembly to the image plane, or by moving elements of the lens assembly. To improve performance, some lenses have a cam system that adjusts the distance between the groups as the lens is focused. Manufacturers call this different things:
Nikon (, ; ), also known just as Nikon, is a Japanese multinational corporation A multinational company (MNC) is a corporate A corporation is an organization—usually a group of people or a company A company, abbreviated as co., is a Lega ...

Nikon
calls it CRC (close range correction);
Canon Canon or Canons may refer to: Places * Canon, Georgia Canon is a city in Franklin County, Georgia, Franklin and Hart County, Georgia, Hart counties in the U.S. state of Georgia (U.S. state), Georgia. The population was 804 at the 2010 census. His ...
calls it a floating system; and
Hasselblad Victor Hasselblad AB is a Swedish Swedish or ' may refer to: * Anything from or related to Sweden, a country in Northern Europe * Swedish language, a North Germanic language spoken primarily in Sweden and Finland * Swedish alphabet, the offi ...

Hasselblad
and
Mamiya is a Japanese company that manufactures high-end cameras and other related photographic and optical equipment. With headquarters in Tokyo, it has two manufacturing plants and a workforce of over 200 people. The company was founded in May 1940 by ...
call it FLE (floating lens element). Glass is the most common material used to construct lens elements, due to its good optical properties and resistance to scratching. Other materials are also used, such as
quartz glass Quartz is a hard, crystalline A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and ...
,
fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride Calcium fluoride is the inorganic compound In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural scien ...

fluorite
, plastics like acrylic (Plexiglass), and even
germanium Germanium is a chemical element with the Symbol (chemistry), symbol Ge and atomic number 32. It is a lustrous, hard-brittle, grayish-white metalloid in the carbon group, chemically similar to its group neighbors silicon and tin. Pure germanium i ...

germanium
and meteoritic glass. Plastics allow the manufacturing of strongly aspherical lens elements which are difficult or impossible to manufacture in glass, and which simplify or improve lens manufacturing and performance. Plastics are not used for the outermost elements of all but the cheapest lenses as they scratch easily. Molded plastic lenses have been used for the cheapest disposable cameras for many years, and have acquired a bad reputation: manufacturers of quality optics tend to use euphemisms such as "optical resin". However many modern, high performance (and high priced) lenses from popular manufacturers include molded or hybrid aspherical elements, so it is not true that all lenses with plastic elements are of low photographic quality. The 1951 USAF resolution test chart is one way to measure the resolving power of a lens. The quality of the material, coatings, and build affect the resolution. Lens resolution is ultimately limited by
diffraction Diffraction refers to various phenomena that occur when a wave In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that ...

diffraction
, and very few photographic lenses approach this resolution. Ones that do are called "diffraction limited" and are usually extremely expensive. Today, most lenses are multi-coated in order to minimize
lens flare Lens flare refers to a phenomenon wherein light is scattered or flared in a lens system, often in response to a bright light, producing a sometimes undesirable artifact within the image. This happens through light scattered by the imaging mec ...

lens flare
and other unwanted effects. Some lenses have a UV coating to keep out the
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that stud ...

ultraviolet
light that could taint color. Most modern optical cements for bonding glass elements also block UV light, negating the need for a UV filter. UV photographers must go to great lengths to find lenses with no cement or coatings. A lens will most often have an aperture adjustment mechanism, usually an
iris diaphragm In optics, a diaphragm is a thin opaque structure with an opening (aperture) at its center. The role of the diaphragm is to ''stop'' the passage of light, except for the light passing through the ''aperture''. Thus it is also called a stop (an ap ...
, to regulate the amount of light that passes. In early camera models a rotating plate or slider with different sized holes was used. These
Waterhouse stop File:Diaphragms Cassells 1911.png, 350px, ''Cassell's Cyclopedia of Photography'' 1911 identifies John Waterhouse of Halifax as the inventor in 1858 of Waterhouse stops, "a separate stop being required for each opening." The Waterhouse stop or Wate ...
s may still be found on modern, specialized lenses. A shutter, to regulate the time during which light may pass, may be incorporated within the lens assembly (for better quality imagery), within the camera, or even, rarely, in front of the lens. Some cameras with leaf shutters in the lens omit the aperture, and the shutter does double duty.


Aperture and focal length

The two fundamental parameters of an optical lens are the
focal length The focal length of an optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...

focal length
and the maximum
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 ray (optics), rays that come to a focus (optics), focus ...

aperture
. The lens' focal length determines the magnification of the image projected onto the image plane, and the aperture the light intensity of that image. For a given photographic system the focal length determines the
angle of view The angle of view is the decisive variable for the visual perception of the size or projection of the size of an object. Angle of view and perception of size The perceived size of an object depends on the size of the image projected onto the ...

angle of view
, short focal lengths giving a wider field of view than longer focal length lenses. A wider aperture, identified by a smaller f-number, allows using a faster shutter speed for the same exposure. The camera equation, or G#, is the ratio of the
radiance In radiometry Radiometry is a set of techniques for measuring ' Measurement is the numerical quantification of the attributes of an object or event, which can be used to compare with other objects or events. The scope and application of meas ...
reaching the camera sensor to the
irradiance In radiometry Radiometry is a set of techniques for measuring ' Measurement is the numerical quantification of the attributes of an object or event, which can be used to compare with other objects or events. The scope and application of measure ...

irradiance
on the focal plane of the camera lens. The maximum usable aperture of a lens is specified as the focal ratio or
f-number In optics, 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 ("clear aperture").Smith, Warren ''Modern Optical Engineering'', 4th Ed., 2007 McGraw-Hill Prof ...
, defined as the lens's
focal length The focal length of an optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...

focal length
divided by the effective aperture (or
entrance pupil In an optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the ...
), a dimensionless number. The lower the f-number, the higher light intensity at the focal plane. Larger apertures (smaller f-numbers) provide a much shallower
depth of field For many cameras, depth of field (DOF) is the distance between the nearest and the farthest objects that are in acceptably sharp focus in an image. The depth of field can be calculated based on focal length The focal length of an optical ...

depth of field
than smaller apertures, other conditions being equal. Practical lens assemblies may also contain mechanisms to deal with measuring light, secondary apertures for flare reduction, and mechanisms to hold the aperture open until the instant of exposure to allow SLR cameras to focus with a brighter image with shallower depth of field, theoretically allowing better focus accuracy. Focal lengths are usually specified in millimetres (mm), but older lenses might be marked in centimetres (cm) or inches. For a given film or sensor size, specified by the length of the diagonal, a lens may be classified as a: *
Normal lens In photography and cinematography, a normal lens is a photographic lens, lens that reproduces a Angle of view, field of view that appears "natural" to a human observer. In contrast, depth compression and expansion with shorter or longer focal lengt ...

Normal lens
: angle of view of the diagonal about 50° and a focal length approximately equal to the image diagonal. *
Wide-angle lens In photography Photography is the art Art is a diverse range of (products of) human activities involving creative imagination to express technical proficiency, beauty, emotional power, or conceptual ideas. There is no generally ag ...
: angle of view wider than 60° and focal length shorter than normal. *
Long-focus lens In photography, a long-focus lens is a camera lens which has a focal length that is longer than the diagonal measure of the film or sensor that receives its image. It is used to make distant objects appear magnification, magnified with magnificat ...
: any lens with a focal length longer than the diagonal measure of the film or sensor. Angle of view is narrower. The most common type of long-focus lens is the
telephoto lens A telephoto lens, in photography Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as p ...
, a design that uses special optical configurations to make the lens shorter than its focal length. A side effect of using lenses of different focal lengths is the different distances from which a subject can be framed, resulting in a different perspective. Photographs can be taken of a person stretching out a hand with a wideangle, a normal lens, and a telephoto, which contain exactly the same image size by changing the distance from the subject. But the perspective will be different. With the wideangle, the hands will be exaggeratedly large relative to the head. As the focal length increases, the emphasis on the outstretched hand decreases. However, if pictures are taken from the same distance, and enlarged and cropped to contain the same view, the pictures will have identical perspective. A moderate long-focus (telephoto) lens is often recommended for portraiture because the perspective corresponding to the longer shooting distance is considered to look more flattering. The widest aperture lens in history of photography is believed to be the Carl Zeiss Planar 50mm f/0.7, which was designed and made specifically for the
NASA The National Aeronautics and Space Administration (NASA; ) is an independent agency A regulatory agency or regulatory authority, is a Public benefit corporation Public-benefit corporation is a term that has different meanings in differen ...

NASA
Apollo Apollo, grc, Ἀπόλλωνος, ''Apóllōnos'', label=genitive , ; , grc-dor, Ἀπέλλων, ''Apéllōn'', ; grc, Ἀπείλων, ''Apeílōn'', label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, ''Áploun'', la, Apollō, ...

Apollo
lunar program to capture the far side of the moon in 1966. Three of these lenses were purchased by filmmaker
Stanley Kubrick Stanley Kubrick (; July 26, 1928 – March 7, 1999) was an American film director, producer, screenwriter, and photographer. He is frequently cited as one of the greatest filmmakers Filmmaking (or, in any context, film production) is ...
in order to film scenes in his movie ''
Barry Lyndon ''Barry Lyndon'' is a 1975 period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Period, a descr ...
'', using candlelight as the sole light source.


Number of elements

The complexity of a lens — the number of elements and their degree of asphericity — depends upon the angle of view, the maximum aperture, and intended price point, among other variables. An extreme wideangle lens of large aperture must be of very complex construction to correct for optical aberrations, which are worse at the edge of the field and when the edge of a large lens is used for image-forming. A long-focus lens of small aperture can be of very simple construction to attain comparable image quality: a doublet (two elements) will often suffice. Some older cameras were fitted with
convertible lens A camera lens (also known as photographic lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media cap ...
es (German: ') of normal focal length. The front element could be unscrewed, leaving a lens of twice the focal length, and half the angle of view and half the aperture. The simpler half-lens was of adequate quality for the narrow angle of view and small relative aperture. Obviously the
bellows A bellow or pair of bellows is a device constructed to furnish a strong blast of air File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by volume, excluding water vapor. Lower pie represents trace gases that together comp ...
had to extend to twice the normal length. Good-quality lenses with maximum aperture no greater than f/2.8 and fixed, normal, focal length need at least three (triplet) or four elements (the trade name "
Tessar The Tessar is a design conceived by the German physicist in 1902 while he worked at the optical company and patented by Zeiss in Germany; the lens type is usually known as the Zeiss Tessar. A Tessar comprises four elements in three groups ...

Tessar
" derives from the
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
''tessera'', meaning "four"). The widest-range zooms often have fifteen or more. The reflection of light at each of the many interfaces between different optical media (air, glass, plastic) seriously degraded the
contrast Contrast may refer to: Science * Contrast (vision), the difference in color and light between parts of an image * Contrast (statistics), a combination of averages whose coefficients add up to zero, or the difference between two means * Behavioral ...
and
color saturation File:Saturation of digital colors.png, 300x300px, 7.5PB and 10BG Munsell hue pages of RGB colors, showing lines of uniform saturation (chroma in proportion to lightness) in red. Note that lines of uniform saturation radiate from near the black ...
of early lenses, particularly zoom lenses, especially where the lens was directly illuminated by a light source. The introduction many years ago of optical coatings, and advances in coating technology over the years, have resulted in major improvements, and modern high-quality zoom lenses give images of quite acceptable contrast, although zoom lenses with many elements will transmit less light than lenses made with fewer elements (all other factors such as aperture, focal length, and coatings being equal).


Lens mounts

Many
single-lens reflex camera A single-lens reflex camera (SLR) is a camera that typically uses a mirror and prism system (hence "reflex" from the mirror's reflection) that permits the photographer to view through the lens and see exactly what will be captured. With twin le ...
s and some
rangefinder camera A rangefinder camera is a camera fitted with a rangefinder The rangefinding telemeter (or simply telemeter or rangefinder, depending on the context), is a device used to measure distances to remote objects, that is, a type of rangefinder ...
s have detachable lenses. A few other types do as well, notably the Mamiya
TLR cameras
TLR cameras
and SLR, medium format cameras (RZ67, RB67, 645-1000s)other companies that produce medium format equipment such as Bronica, Hasselblad and Fuji have similar camera styles that allow interchangeability in the lenses as well, and
mirrorless interchangeable-lens camera A mirrorless interchangeable-lens camera (MILC) or simply mirrorless camera, also called digital single-lens mirrorless (DSLM), is a photo camera A camera is an Optics, optical instrument used to capture an image. At their most basic, c ...
s. The lenses attach to the camera using a lens mount, which contains mechanical linkages and often also electrical contacts between the lens and camera body. The lens mount design is an important issue for compatibility between cameras and lenses. There is no universal standard for lens mounts, and each major camera maker typically uses its own proprietary design, incompatible with other makers. A few older manual focus lens mount designs, such as the
Leica
Leica
M39 lens mount M39, M-39 or M.39 may refer to: Aviation * Macchi M.39 The Macchi M.39 was a racing seaplane A seaplane is a powered fixed-wing aircraft capable of taking off and landing of Ryanair makes a smoky landing at Bristol Airport (201 ...
for rangefinders,
M42 lens mount The M42 lens mount A lens mount is an interface – mechanical and often also electrical – between a photographic camera body and a lens. It is a feature of camera systems where the System camera, body allows interchangeable lenses, most u ...
for early SLRs, and the
Pentax K mount The Pentax K-mount, sometimes referred to as the "PK-mount", is a bayonet A bayonet (from French ''baïonnette'') is a knife A knife (plural knives; from Old Norse Old Norse, Old Nordic, or Old Scandinavian is a stage of develo ...
are found across multiple brands, but this is not common today. A few mount designs, such as the Olympus/
Kodak The Eastman Kodak Company (referred to simply as Kodak ) is an American public company that produces various products related to its historic basis in analogue photography. The company is headquartered in Rochester, New York Rochester ( ...

Kodak
Four Thirds System The Four Thirds System is a standard created by Olympus and Eastman Kodak The Eastman Kodak Company (referred to simply as Kodak ) is an American public company A public company, publicly traded company, publicly held company, publicl ...
mount for DSLRs, have also been licensed to other makers.Guy 2012, page 266 Most large-format cameras take interchangeable lenses as well, which are usually mounted in a lensboard or on the front standard. The most common interchangeable lens mounts on the market today include the Canon
EF
EF
,
EF-S The Canon EF-S lens mount is a derivative of the Canon EF lens mount, EF lens mount created for a subset of Canon Inc., Canon digital single-lens reflex cameras with APS-C sized image sensors. It was released in 2003. Cameras with the EF-S mount ar ...
and EF-M autofocus lens mounts, the Nikon F manual and autofocus mounts, the Olympus/Kodak Four Thirds and Olympus/Panasonic
Micro Four Thirds Micro may refer to: Measurement * micro- Micro- (Greek letter μ or legacy micro symbol µ) is a unit prefixA unit prefix is a specifier or mnemonic that is prepended to units of measurement to indicate multiples or fractions of the units. Units ...
digital-only mounts, the
Pentax K mount The Pentax K-mount, sometimes referred to as the "PK-mount", is a bayonet A bayonet (from French ''baïonnette'') is a knife A knife (plural knives; from Old Norse Old Norse, Old Nordic, or Old Scandinavian is a stage of develo ...
and autofocus variants, the Sony
Alpha Alpha (uppercase , lowercase ; grc, ἄλφα, ''álpha'', modern pronunciation ''álfa'') is the first letter Letter, letters, or literature may refer to: Characters typeface * Letter (alphabet) A letter is a segmental symbol A s ...
mount (derived from the
Minolta was a Japanese manufacturer of cameras, camera accessories, photocopiers, fax machines, and laser printers. Minolta Co., Ltd., which is also known simply as Minolta, was founded in Osaka, Japan, in 1928 as . It made the first integrated autofocu ...
mount) and the Sony E digital-only mount.


Types of lens


"Close-up" or macro

A macro lens used in
macro Macro (or MACRO) may refer to: Science and technology * Macroscopic The macroscopic scale is the length scale on which objects or phenomena are large enough to be visible with the naked eye, without magnifying optical instruments. It is the o ...

macro
or "close-up" photography (not to be confused with the compositional term ''
close up A close-up or closeup in filmmaking Filmmaking (film production) is the process by which a motion picture A film, also called a movie, motion picture or moving picture, is a work of visual art The visual arts are art forms s ...

close up
'') is any lens that produces an image on the focal plane (i.e., film or a digital sensor) that is one quarter of life size (1:4)to the same size (1:1) as the subject being imaged. There is no official standard to define a macro lens, usually a
prime lens In film and photography, a prime lens is a fixed focal length The focal length of an optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, ...
, but a 1:1 ratio is, typically, considered "true" macro. Magnification from life size to larger is called "Micro" photography (2:1, 3:1 etc.). This configuration is generally used to image ''close-up'' very small subjects. A macro lens may be of any focal length, the actual focus length being determined by its practical use, considering magnification, the required ratio, access to the subject, and illumination considerations. It can be a special lens corrected optically for close up work or it can be any lens modified (with adapters or spacers, which are also known as "extension tubes".) to bring the focal plane "forward" for very close photography. Depending on the camera to subject distance and aperture, the depth-of-field can be very narrow, limiting the linear depth of the area that will be in focus. Lenses are usually stopped down to give a greater depth-of-field.


Zoom

Some lenses, called zoom lenses, have a focal length that varies as internal elements are moved, typically by rotating the barrel or pressing a button which activates an
electric motor
electric motor
. Commonly, the lens may zoom from moderate wide-angle, through normal, to moderate telephoto; or from normal to extreme telephoto. The zoom range is limited by manufacturing constraints; the ideal of a lens of large maximum aperture which will zoom from extreme wideangle to extreme telephoto is not attainable. Zoom lenses are widely used for small-format cameras of all types: still and cine cameras with fixed or interchangeable lenses. Bulk and price limit their use for larger film sizes. Motorized zoom lenses may also have the focus, iris, and other functions motorized.


Special-purpose

*
Apochromat An apochromat, or apochromatic lens (apo), is a Photographic lens, photographic or other Lens (optics), lens that has better correction of chromatic aberration, chromatic and spherical aberration than the much more common achromat lenses. Explana ...

Apochromat
(apo) lenses have added correction for
chromatic aberration In optics Optics is the branch of that studies the behaviour and properties of , including its interactions with and the construction of that use or it. Optics usually describes the behaviour of , , and light. Because light is an , oth ...

chromatic aberration
. * Process lenses have extreme correction for aberrations of geometry (
pincushion distortion
pincushion distortion
,
barrel distortion Image:Uniformity.jpg, Wine glasses creating a non-uniform distortion of their background In geometric optics, distortion is a deviation from rectilinear projection; a projection in which straight lines in a scene remain straight in an image. It ...

barrel distortion
) and are generally intended for use at a specific distance and at small aperture. * Enlarger lenses are made to be used with
photographic enlarger An enlarger is a specialized transparency projector used to produce photographic prints from film or glass negatives, or from transparencies. Construction All enlargers consist of a light source, normally an incandescent light bulb shining tho ...
s (specialised projectors), rather than cameras. * Lenses for
aerial photography Aerial photography (or airborne imagery) is the taking of photographs from an aircraft or other flying object. Platforms for aerial photography include fixed-wing aircraft, helicopters, unmanned aerial vehicles (UAVs or "drones"), Balloon (aircr ...
. * Shift lens allow the lens to be raised or lowered relative to the film of sensor plane to correct or exaggerate perspective distortion. *
Fisheye lens A fisheye lens is an ultra wide-angle lens that produces strong visual distortion intended to create a wide panoramic or hemispherical of a sphere A sphere (from Greek language, Greek —, "globe, ball") is a Geometry, geometrical object in ...
es: extreme wide-angle lenses with an angle of view of up to 180 degrees or more, with very noticeable (and intended) distortion. * Stereoscopic lenses, to produce pairs of photographs which give a 3-dimensional effect when viewed with an appropriate viewer. * Soft-focus lenses which give a soft, but not out-of-focus, image and have an imperfection-removing effect popular among portrait and fashion photographers. * Infrared lenses * Ultraviolet lenses * Swivel lenses rotate while attached to a camera body to give unique perspectives and camera angles. * Shift lenses and tilt/shift lenses (collectively
perspective control lens Perspective may refer to: Vision and mathematics * Perspectivity, the formation of an image in a picture plane of a scene viewed from a fixed point, and its modeling in geometry ** Perspective (graphical), representing the effects of visual perspe ...
es) allow special control of perspective on SLR cameras by mimicking view camera movements.


History and technical development of photographic camera lenses


Lens designs

Some notable photographic optical lens designs are: * Angenieux retrofocus *
Cooke triplet The Cooke triplet is a photographic lens designed and patented (patent number GB 22,607) in 1893 by Harold Dennis Taylor, Dennis Taylor who was employed as chief engineer by Cooke of York, T. Cooke & Sons of York. It was the first lens system tha ...

Cooke triplet
* Double-Gauss * Goerz Dagor * Leitz Elmar * Rapid Rectilinear * Zeiss Sonnar * Zeiss Planar * Zeiss Tessar


See also

* Anti-fogging treatment of optical surfaces * Large format lens * Lens (optics) * Lens hood * Lens cover * Lenses for SLR and DSLR cameras * Teleconverter * Teleside converter * William Taylor (inventor) * Optical train


References


Sources

* *


External links


Photo.net Lens Tutorial


{{DEFAULTSORT:Camera Lens Photographic lenses,