Perspective correction lens
5250282
225628181
2008-07-14T17:03:48Z
Trbgln
1295199
[[image:35mmPC500.jpg|thumb|252px|right|The world’s first PC lens in the [[135 film|35 mm format]]: the 1961 [[Nikon F-mount|F-mount]] 35 mm {{f/|3.5|link=yes}} PC-[[Nikkor]] that shifts up to 11 mm in any direction.]]
In [[photography]], a '''perspective correction lens''' (also known as a '''PC lens''', '''perspective control lens''', or '''shift lens''', or — if the lens can also tilt — a '''tilt and shift''' or '''TS lens''') allows the photographer to correct for the effects of [[perspective (visual)|perspective]] by shifting the lens in relationship to the [[Photographic_film|film]] or [[image sensor|sensor]] area. This type of [[photographic lens|lens]] is mostly used in architectural and other technical photography. Perspective control lenses are generally made for [[single-lens reflex]] (SLR) [[35 mm film|35 mm]] and [[Medium format (film)|medium-format]] SLR cameras, as most [[large format]] cameras allow for [[perspective correction]] using [[View camera#Movements|movements]].
A perspective control lens has a larger [[image circle]] than is required to cover the image area (film or sensor size). Typically, the image circle is large enough, and the mechanics of the lens sufficiently limited, that the film plane cannot be shifted outside of the image area. However, all PC lenses require a small [[aperture]] setting to prevent [[vignetting]] when significant shifts are employed. PC lenses for 35 mm cameras typically offer a maximum shift of 11 mm.
The first PC lens manufactured for an SLR camera in any format was [[Nikon F-mount|Nikon]]’s 1961 {{f/}}3.5 35 mm PC-Nikkor; it was followed by an {{f/}}2.8 35 mm PC-Nikkor (1968), an {{f/}}4 28 mm PC-Nikkor (1975), and an {{f/}}3.5 28 mm PC-Nikkor (1981).<ref>{{cite web | title = Tale Seventeen : PC-Nikkor 28 mm f/4 | publisher = [[Nikon|Nikon Corporation]] | url = http://imaging.nikon.com/products/imaging/technology/nikkor/n17_e.htm}}</ref> In 1973, [[Canon (company)|Canon]] introduced a lens, the TS 35 mm {{f/}}2.8 SSC,<ref>
[http://www.canon.com/camera-museum/camera/lens/fd/data/17-35/ts_35_28_ssc.html Canon TS 35 mm {{f/}}2.8 SSC lens].
[http://www.canon.com/camera-museum/ Canon Camera Museum]
</ref>
with tilt as well as shift functions.
Other manufacturers, including [[Olympus Corporation|Olympus]], [[Pentax]], [[Schneider Kreuznach]] (produced as well for [[Leica]]), and [[Minolta]], made their own versions of PC lenses. Olympus produced 35 mm and 24 mm shift lenses. Canon currently offers 24 mm, 45 mm, and 90 mm tilt/shift lenses. Nikon currently offers 24 mm, 45 mm, and 85 mm PC lenses with tilt and shift capability.
==Applications==
{|align="right" style="border:1px solid #000; padding:2px; background-color:#F9F9F9; width:250px; font-size:90%"
|[[Image:Pc-lens-demo-tiltedcamera.svg|250px]]
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|('''a''') Tilting the camera upwards results in vertical perspective.
|-
|[[Image:Pc-lens-demo-levelcamera.svg|250px]]
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|('''b''') Keeping the camera level, with an ordinary lens, captures only the bottom portion of the building.
|-
|[[Image:Pc-lens-demo-lensshifted.svg|250px]]
|-
|('''c''') Shifting the lens upwards results in a picture of the entire subject.
|}
When making photographs of a building or other large structure from the ground, it is often impossible (without shift) to fit the entire building in the frame without tilting the camera upwards. The resultant perspective causes the top of the building to appear smaller than its base, which is often considered undesirable ('''a'''). The perspective effect is proportional to the lens’s angle of view.
Photographing from the ground, perspective can be eliminated by keeping the film plane parallel to the building. With ordinary lenses, this results in capturing only the bottom part of the subject ('''b'''). With a perspective control lens, however, the lens may be shifted upwards in relation to the film plane, placing more of the subject within the frame ('''c'''). The ground level, the camera’s point of perspective, is shifted towards the bottom of the frame.
Another use of shifting is in taking pictures of a mirror. By moving the camera off to one side of the mirror, and shifting the lens in the opposite direction, an image of the mirror can be captured without the reflection of the camera or photographer. Shifting can similarly be used to photograph “around” an object, such as a building support in a gallery, without producing an obviously oblique view.
==Available lenses==
The earliest perspective control and tilt/shift lenses for 35 mm format were 35 mm focal length, which is now considered too long for many architectural photography applications. With advances in optical design, lenses of 28 mm and then 24 mm became available and were quickly adopted by photographers working in close proximity to their subjects, such as in urban settings.
Canon offers three lenses with tilt and shift functions: the TS-E 24 mm {{f/}}3.5L, the TS-E 45 mm {{f/}}2.8, and the TS-E 90 mm {{f/}}2.8; the 90 mm lens gives 0.29 magnification. All three lenses provide automatic aperture control.
Nikon offers four lenses with tilt and shift functions: the PC-E Nikkor 24 mm {{f/}}3.5D ED, the PC-E Micro Nikkor 45 mm {{f/}}2.8D ED, the PC-E Micro Nikkor 85 mm {{f/}}2.8D, and the PC Micro-Nikkor 85 mm {{f/}}2.8D; the 45 mm and 85 mm lenses offer close focus (0.5 magnification) for [[macrophotography]]. The PC-E lenses offer automatic aperture control with the Nikon D3, D300, and D700 cameras; with earlier camera models, the lenses offer preset aperture control by means of a pushbutton. The PC Micro-Nikkor 85 mm {{f/}}2.8D lens offers only preset aperture control. Among Nikon's [[Digital single-lens reflex camera|digital SLRs]], only the D3 and D700 have Nikon’s FX-format (23.9 mm × 36 mm) [[Image sensor format|sensor]] to enable the full capabilities of these lenses.
On both the Canon and Nikon lenses, the mechanisms providing the tilt and shift functions can be rotated 90° to the left or right so that they operate horizontally, vertically, or at intermediate orientations. The lenses are supplied with the tilt and shift movements at right angles to each other; they can be modified so that the movements operate in the same direction.
[[Hartblei]] makes tilt-and-shift lenses to fit various manufacturers’ camera bodies. It currently offers four Super-Rotator Tilt/Shift lenses for 35 mm bodies: the TS-PC Hartblei 35 mm {{f/}}2.8, the TS-PC Hartblei 65 mm {{f/}}3.5, the TS-PC Hartblei 80 mm {{f/}}2.8, and the TS-PC Hartblei 120 mm {{f/}}2.8. It also offers the TS-PC Hartblei 45 mm {{f/}}3.5 to fit several medium-format camera bodies. The tilt and shift movements can be independently rotated in any direction.
<!-- Get rid of "announced" when adapter becomes available -->
In July 2008, [[Hasselblad]] announced a tilt and shift adapter, the HTS 1.5, for use with the HCD 28 mm {{f/}}4, HC 35 mm {{f/}}3.5, HC 50 mm {{f/}}3.5, and HC 80 mm {{f/}}2.8 lenses on [[Hasselblad#H-System|H-System]] cameras. To allow infinity focus, the adapter includes optics that multiply the lens focal lengths by 1.5. Autofocus and focus confirmation are disabled when using the adapter.
Schneider-Kreuznach offers the PC-Super Angulon 28 mm {{f/}}2.8 lens that provides shift movements, with preset aperture control. The lens is available with mounts to fit cameras by various manufacturers, and also with 42 mm screw mount.
All perspective control and tilt/shift lenses are [[manual focus|manual-focus]] [[prime lens]]es; most are quite expensive compared to regular prime lenses. Some [[medium format (film)|medium format]] camera makers, such as [[Mamiya]], have addressed this problem by offering shift adapters that work with the maker’s other prime lenses.
==Aperture control==
The first SLR cameras with internal ([[Through-the-lens metering|“through-the-lens” or “TTL”]])
meters required that the lens be stopped down to working aperture when
taking a meter reading. With a small aperture, this darkened the
viewfinder, making viewing and composition difficult.<ref>
Shipman, Carl. ''SLR Photographers Handbook''. Tucson, AZ: HP Books, 1977, p. 53. ISBN 0-912656-59-X
</ref>
Subsequent models
soon incorporated mechanical coupling between the lens and the camera body,
indicating the set aperture to the camera while allowing the lens to be at
its maximum aperture for composition and focusing. A scene could be
metered at full aperture, and the camera would set the lens to the working
aperture at the time of exposure. This feature became known as automatic
aperture control.
For some lenses, including a few long telephotos, lenses mounted on
bellows, and perspective-control and tilt/shift lenses, the mechanical
linkage was impractical, and automatic aperture control was not
possible. Many such lenses incorporated a feature known as a “preset”
aperture,<ref>
Peterson, B. “Moose”.
''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
PC Nikkor 35 mm {{f/}}2.8, 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.
When Canon introduced its [[Canon EOS|EOS]] line of cameras in 1987, the
[[Canon EF mount|EF]] lenses incorporated electromagnetic diaphragms,
eliminating the need for a mechanical linkage between the camera and the
diaphragm. Because of this, the Canon TS-E tilt/shift lenses include
automatic aperture control.
In 2008, Nikon introduced its PC-E perspective-control lenses with
electromagnetic diaphragms. Automatic aperture control is provided with
the [[D300]], [[D3]], and [[D700]] cameras; with earlier cameras, the
lenses offer preset aperture control by means of a pushbutton that
controls the electromagnetic diaphragm.
==Perspective correction in software==
{{main|Perspective correction}}
Computer software (such as [[Photoshop]]'s ''perspective'' and ''distort'' functions) can be used to correct perspective effects in [[post-production]], but cannot recover lost [[optical resolution]] in the more distant portions of the subject.
==Gallery of perspective control lenses==
<gallery>
Image:24mmPCleft.jpg|[[Olympus]] 24 mm {{f/}}3.5 Zuiko-Shift. 10 mm maximum shift,. Mounted on an Olympus camera.
Image:28mm-PC.jpg|[[Nikon]] 28 mm {{f/}}3.5 PC-[[Nikkor]]. 11 mm maximum shift. Mounted on a [[Nikon F5]]
Image:PC_Nikkor_35mm.jpg|[[Nikon]] 35 mm {{f/}}2.8 PC-[[Nikkor]]. 11 mm maximum shift.
Image:Canon TS-E24mm F3.5L.jpg|[[Canon (company)|Canon]] [[TS-E24mm f/3.5L|TS-E 24 mm {{f/}}3.5L]]. 11 mm maximum shift. 8° maximum tilt.
Image:Minolta-shift-lens.jpg|[[Minolta]] 35 mm {{f/}}2.8 Shift lens, 11 mm maximum shift.
Image:PA-Curtagon.jpg|[[Schneider Kreuznach|Schneider]] 35 mm {{f/}}4 PA-Curtagon. 7 mm maximum shift. Also rebadged by [[Leica]]
Image:28mm-SMC-Pentax-Shift.jpg|[[Pentax]] Shift 28 mm {{f/}}2.8 SMC lens.
Image:Pentaxshift.jpg|[[Pentax]] Shift 6x7 75 mm {{f/}}4.5. 20 mm maximum shift. Mounted on a Pentax 6x7 [[medium-format]] [[Single-lens reflex|SLR]].
</gallery>
==References==
<references />
==External links==
* [http://www.f-stop.com/p-c.htm What is perspective correction?]
* [http://www.photo.net/equipment/canon/tilt-shift How Shift Lenses Change your Life]
* [http://www.uscoles.com/pclens.htm Using the 35 mm Perspective Control Lens]
* [http://photonotes.org/cgi-bin/entry.pl?id=Perspectivecontrollens PhotoNotes.org]
* [http://www.panoramafactory.com/shiftlens/shiftlens.html Using a perspective control lens (shift lens)]
* [http://www.danheller.com/tech-persp.html Tutorial: Perspective Control Lenses]
* [http://www.photosig.com/articles/1207/article;jsessionid=aNNvR4tqj3o-iTjaJI Perspective Correction Using Software]
* [http://hame.ca/tiltshift.htm Page of Links to Galleries and Information on Tilt-Shift Photography and Lenses]
==External links—specific lenses and adapters==
* [http://www.ohse.de/uwe/articles/shift-tilt.html Shift/Tilt Lenses for 35 mm Cameras]
* [http://www.canon.com/camera-museum/camera/lens/ef/data/ts-e/ts_e24_35l.html Canon TS-E 24 mm {{f/}}3.5L lens]
* [http://www.canon.com/camera-museum/camera/lens/ef/data/ts-e/ts_e45_28.html Canon TS-E 45 mm {{f/}}2.8 lens]
* [http://www.canon.com/camera-museum/camera/lens/ef/data/ts-e/ts_e90_28.html Canon TS-E 90 mm {{f/}}2.8 lens]
* [http://www.hartblei.com/lenses/general_info.htm Hartblei Super-Rotator Tilt Shift lenses]
* [http://www.hasselbladusa.com/products/h-system/hts-15.aspx Hasselblad HTS 1.5 tilt and shift adapter]
* [http://members.aol.com/cldphoto/shift_ca.html Minolta 35 mm {{f/}}2.8 Shift lens]
* [http://www.mir.com.my/rb/photography/companies/nikon/nikkoresources/PC_Nikkor/index4.htm PC-Nikkor 28 mm {{f/}}3.5 lens]
* [http://www.mir.com.my/rb/photography/companies/nikon/nikkoresources/PC_Nikkor/index1.htm PC-Nikkor 35 mm {{f/}}3.5 and {{f/}}2.8 lenses]
* [http://www.nikonusa.com/Find-Your-Nikon/ProductDetail.page?pid=2168 PC-E Nikkor 24 mm {{f/}}3.5D ED lens]
* [http://www.nikonusa.com/Find-Your-Nikon/Product/Camera-Lenses/2174/PC-E-Micro-NIKKOR-45mm-f/2.8D-ED.html PC-E Micro Nikkor 45 mm {{f/}}2.8D ED lens]
* [http://www.nikonusa.com/Find-Your-Nikon/Product/Camera-Lenses/2175/PC-E-Micro-NIKKOR-85mm-f/2.8D.html PC-E Micro Nikkor 85 mm {{f/}}2.8D ED lens]
* [http://www.mir.com.my/rb/photography/hardwares/classics/olympusom1n2/shared/zuiko/htmls/24mmSHIFT.htm Olympus 24 mm Zuiko-Shift lens]
* [http://www.pbase.com/jamesk8752/k28shift SMC Pentax Shift 28 mm {{f/}}2.8 lens]
* [http://www.schneideroptics.com/ecommerce/CatalogSubCategoryDisplay.aspx?CID=179 Schneider-Kreuznach PC-Super Angulon 28 mm {{f/}}2.8 lens]
[[Category:Photographic lenses]]
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