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Topic: Photographic lens


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In the News (Thu 18 Apr 19)

  
  NationMaster - Encyclopedia: Photographic lens
Convex lens converging light rays A convex lens, or converging lens, is a lens that is curved outward (convex): the ends are narrow and the middle is wide.
The lens may usually be focused by adjusting the distance from the lens assembly to the image-forming surface, or by moving elements within the lens assembly.
An aspheric lens or asphere is a lens whose surfaces have a profile that is neither a portion of a sphere nor of a circular cylinder.
www.nationmaster.com /encyclopedia/Photographic_lens   (2923 words)

  
 Reference.com/Encyclopedia/Photographic lens
A photographic lens (also known as objective 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 capable of storing an image chemically or electronically.
The maximum usable aperture of a lens is usually specified as the focal ratio or f-number, which is equal to the focal length divided by the effective aperture (or entrance pupil) diameter in the same units.
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.
www.reference.com /browse/wiki/Photographic_lens   (1898 words)

  
  Photographic lens - Wikipedia, the free encyclopedia
The lens may usually be focused by adjusting the distance from the lens assembly to the image-forming surface, or by moving elements within the lens assembly.
The maximum usable aperture of a lens is usually specified, as the focal ratio or f-number, which is equal to the focal length divided by the actual aperture diameter in the same units.
The two main optical parameters of a photographic lens are the focal length and the maximum aperture.
en.wikipedia.org /wiki/Photographic_lens   (1292 words)

  
 Photography - Wikipedia, the free encyclopedia
Photographers control the camera to expose the light recording material (usually film or a charge-coupled device) to light.
For example, using a long lens and a large aperture, such as might be used with a large format camera, a subject's eyes might be in sharp focus while the tip of his nose is noticeably blurred.
The first photograph is considered to be an image produced in 1826 by the French inventor Nicéphore Niépce on a polished pewter plate covered with a petroleum derivative called bitumen of Judea.
en.wikipedia.org /wiki/Photography   (3879 words)

  
 PHOTOGRAPHIC LENS
Photographic catadioptric lens with multi-layer anti-reflection coating of the optical surfaces is designed as an interchangeable lens for reflex cameras with 24x36 mm frame size.
The lens focusing is performed by rotation the focusing ring until the sharpest possible image of the object is obtained on the ground glass.
The lens is designed for photographing at the temperature from -15°C to +45°C. when bringing the lens from the cold into a warm room, don't open its case to prevent fogging of optical details.
www.rugift.com /photocameras/manuals/rubinar_5_6_500.htm   (575 words)

  
 Photographic Lenses; Wideangle and Telephoto Lens, Differences?
In contrast, in a telephoto lens, as focal lengths become longer, less difference is observed between close and distant subjects, making it appear as if they are closer regardless of the distance between them(compressed perspective).
A macro lens is designed to capture a tiny subject as a bigger image, while suppressing the aberrations that tend to be more noticeable in closer focusing distances.
This is the case even for those made for a zoom lens, where the wide-end of the focal length range inevitably becomes the benchmark for the optical design.
www.tamron.com /lenses/fundamentals.asp   (1025 words)

  
 Glossary
Since the refraction of an air lens is opposite that of a glass lens, a convex shape acts as a concave lens and a concave shape acts as a convex lens.
The aperture of a lens is related to the diameter of the group of light rays passing through lens and determines the brightness of the subject image formed on the focal plane.
The peripheral image is formed by groups of light rays entering the lens at a certain angle with respect to the optical axis, and the amount of light fall-off is proportional to the cosine of that angle raised to the fourth power.
www.usa.canon.com /html/eflenses/lens101/glossary/index_a.html   (2578 words)

  
 Photographic Lenses Tutorial
While most lens formulas expect the subject distance to be measured from the front principal point, most focusing scales are calibrated to read the distance from the subject to the film plane.
The angle of refraction is proportional the distance from the center at which the ray strikes the plane and inversely proportional to the focal length of the lens.
Equivalently, the modulation transfer function of a lens is the ratio of relative image contrast divided by relative subject contrast of a subject with sinusoidally varying brightness as a function of spatial frequency (e.g.
www.graflex.org /lenses/photographic-lenses-tutorial.html   (4883 words)

  
 Lenses
Focusing occurs because the lens is able to precisely control this direction so that the light rays converge on one point, exactly where the film is located in the camera (or where the CCD is, in the case of a digital camera.)
By definition, what we commonly call a photographic lens is more accurately and technically called an “objective.” An objective (or object lens, object glass, objective lens or photographic objective) is an optical system or device containing a combination of lenses that receive light rays from an object and form an image on the focal plane.
A photographic lens is composed of lenses (ground and polished pieces of formed optical glass) assembled and fitted together in a tube (usually made of metal) called a "lens barrel".
www.photographytips.com /page.cfm/466   (859 words)

  
 ipedia.com: Photography Article   (Site not responding. Last check: 2007-10-16)
Most commonly a camera or camera obscura is the image forming device and photographic film or a digital storage card is the recording medium, but other methods are available.
The first photograph is considered to be an image produced in 1825 by Nicéphore Niepce; on a polished pewter plate covered with a petroleum derivative called bitumen of Judea.
Camera obscura were used by artists in the 16th century, as an aid to sketches for paintings, and the photo-sensitivity of a silver nitrate solution was observed by Johann Schultze in 1724.
www.ipedia.com /photography.html   (1131 words)

  
 Photographic lens - Definition, explanation
A photographic lens (or more correctly, objective) is an integrated system comprising one or more simple optical lens elements, used for a camera or microscope.
There will usually be an aperture selection mechanism for adjusting the amount of light through the lens, and a focusing mechanism.
Nowadays, it is usually measured in millimeters (mm), but up to around 1960, the centimeter (cm) was common, and older used lenses with focal lengths marked in inches are still available.
www.calsky.com /lexikon/en/txt/p/ph/photographic_lens.php   (777 words)

  
 Photographic Lens and Filter Cleaning
Fluorite (a lens material used by Canon in their "L" series telephoto lenses) isn't very hard at all, and that's at least one reason why fluorite lens elements are used between regular glass elements.
If a fluorite element was used as the front element in a lens it would easily scratch, so if the design calls for that, a permanent multicoated flat glass "filter" element is used in front of it - and that's why some of the long Canon telephotos use such a fixed "filter".
Lens cloths should be washed frequently and kept in a clean plastic bag when not in use.
www.bobatkins.com /photography/tutorials/lens_filter_cleaning.html   (1515 words)

  
 Photographic Lenses Tutorial
While most lens formulas expect the subject distance to be measured from the front principal point, most focusing scales are calibrated to read the distance from the subject to the film plane.
The angle of refraction is proportional the distance from the center at which the ray strikes the plane and inversely proportional to the focal length of the lens.
Equivalently, the modulation transfer function of a lens is the ratio of relative image contrast divided by relative subject contrast of a subject with sinusoidally varying brightness as a function of spatial frequency (e.g.
web.telia.com /~u54105795/FAQphoto_lenses_tutorial.html   (4852 words)

  
 News from CSC   (Site not responding. Last check: 2007-10-16)
A macro lens is designed to capture a tiny subject as a bigger image, while suppressing the aberrations that tend to be more noticeable in closer focusing distances.
A simple adjustment to the zoom and focus on a Vari-focal lens is all that is needed to rectify the situation on the spot: a less costly and time-consuming prospect than having to order and install a different monofocal lens altogether.
Lens hoods are designed as an integral part of the optics to provide the maximum shading for each lens.
www.gocsc.com /enews/november05/news/tech   (1228 words)

  
 Lens Maintenance
Lens cement can be dissolved with acetone and new cement can be obtained, but you must cement elements so that their optical centers coincide and insure that no foreign material is trapped between the elements.
Lay a piece of lens cleaning paper or tissue on the lens and squeeze one or two drops of fluid on the paper, then pull the wet paper across the lens.
Lens caps are generally a good thing, unless they are made from materials that can contaminate lens surfaces and coatings.
www.prairienet.org /b-wallen/BN_Photo/GenTechLenses.htm   (1540 words)

  
 Sphæra issue no. 8: article 7
The lens in the Museum's collection is a specimen of the earliest panoramic wide-angle lens ever produced, patented by Sutton on the 28th September, 1859.
Ross purchased Sutton's lens patent from him in August and by November was advertising the camera in a total of three different sizes.
The lens is fitted with a central stop of f12 and the shutter is of a very simple construction, consisting of a mahogany flap that hinges in front of the lens.
www.mhs.ox.ac.uk /sphaera/issue8/articl7.htm   (1253 words)

  
 Photography: Share, Learn, Create in the Photography.com Community
A zoom lens allows the photographer to widen or shorten the lens’ focal length to increase or decrease the magnification of the subject.
In contrast, a telephoto lens brings the subject “closer” to the photographer, reducing the distance between objects in the photograph and the camera’s lens.
The fisheye lens was first developed for astronomy photography that seeks to capture as wide a range of sky as possible.
www.photography.com /topics/choosing-lenses   (989 words)

  
 Contax Lens Design
He was awarded the first patent for lens coating in 1903 for a chemical or acid fuming process that was highly unreliable, and the components very caustic.
This was a Hybrid lens type, consisting of a front component which was a ordinary two meniscus element Gauss type, and the rear component was the rear half of a Plasmat.
This is a reversed telephoto lens, consisting of a large negative lens in front of an ordinary lens.
www.panix.com /~zone/photo/czlens.htm   (4970 words)

  
 photographic lens apertures   (Site not responding. Last check: 2007-10-16)
Currently this adjustment is almost always calibrated in f-stops or f-numbers, which, roughly speaking, are the diameter of the glass at the front of the lens divided by the diameter of the hole made by the iris diaphragm.
To double the amount of light passing through the lens, the area of the aperture must double, and for that the new diameter of the aperture must be the square root of 2 (1.414…) times the old diameter, because the area of a circle varies as the square of its radius.
A lens has its maximum possible resolution at its widest aperture, but in practice, as a rule of thumb a lens is sharpest about 2 whole stops below its widest aperture.
www.sizes.com /tools/photoaper.htm   (458 words)

  
 Fungi in Photographic Lens
With some lens mounts this may mean moving a lever, or even mounting the lens on a camera and looking into the front of the lens.
Leather lens cases are known to be especially bad, because leather is a natural product where fungi can grow before they proceed on to the lens.
The first infected lens I dealt with was badly etched so that it was optically bad after cleaning; from this I assumed that fungus would always be unrecoverable and avoided lenses with any trace of it.
www.chem.helsinki.fi /~toomas/photo/fungus   (2147 words)

  
 Patents in Class 359/764
Collimator lens and optical scanning apparatus using the same
Vari-focal photographic lens system of rear lens group exchange type
Tele-objective lens with a movable sub-group for focusing
www.freepatentsonline.com /CCL359-764.html   (103 words)

  
 [No title]
Since most lenses are constructed solely of lens elements with spherical surfaces, light rays from a single subject point are not formed in the image as a perfect point.
There are many requirements related to changes in angle of view (especially with wide-angle, zoom and telephoto lenses).
Lens data for EF lenses generally includes the horizontal (36mm) angle of view and vertical (24mm) angle of view in addition to the diagonal angle of view.
consumer.usa.canon.com /ir/controller?act=GlossaryAct&fcategoryid=216   (2509 words)

  
 S.K. Grimes - Mounting an Artar photographic lens in a Copal Shutter
The distance from the front of the lens to the back of the rear threaded adapter is now accuratly acheived.
Using a digital dividing engraver the iris scale is engraved onto the new shutter, duplicating the apertures in the original barrel.
I can also extrapolate the scale to add a smaller f-stop (f-64 in addition to f-45, etc.) On Copal shutters the scales are engraved on both sides as intended in the design of the shutter.
www.skgrimes.com /lensmount/24art   (571 words)

  
 Nikkor 200 mm F2.0 AF-S VR lens: Digital Photography Review
This promises to be a very interesting and very sharp lens which will provide photographers with some great possibilities for shots with very nice soft bokeh.
The system comprises of a suspended lens element that is positioned according to data from gyroscopic sensors and that compensates for accidental vertical or horizontal movement during slow shutter exposures.
The use of such teleconverters with a wide aperture lens is an ideal way of adding extra focal length versatility without the expense and weight of additional lenses.
www.dpreview.com /news/0405/04052801nikkor200.asp   (1216 words)

  
 Cooke History: 1890s Cooke Triplet   (Site not responding. Last check: 2007-10-16)
Having no desire to enter the photographic lens business, T. Cooke and Sons offered the manufacturing rights to Taylor, Taylor and Hobson of Leicester, optical instrument makers who had a reputation for producing quality optical products since 1886 when William Taylor founded the company in Leicester with his brother, Thomas Smithies Taylor.
The first Cooke photographic lens was made by TTandH in 1894 based on Dennis Taylor’s Cooke Triplet patent of 1893.
TTandH went on to produce subsequent lens designs by Dennis Taylor through Series V. The licensing agreement stated that the lenses would be sold under the trade name "Cooke".
www.cookeoptics.com /cooke.nsf/active/0EABFF909955D1E685256E8500295708   (406 words)

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