Perspective correction lens - AbsoluteAstronomy.com

(a) Keeping the camera level, with an ordinary lens, captures only the bottom portion of the building.

(b) Tilting the camera upwards results in vertical perspective.

Photography

Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...

, a perspective control lens allows the photographer to control the appearance of perspective

Perspective (visual)

Perspective, in context of vision and visual perception, is the way in which objects appear to the eye based on their spatial attributes; or their dimensions and the position of the eye relative to the objects...

in the image; the lens can be moved parallel to the film

Photographic film

Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...

or sensor

Image sensor

An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras and other imaging devices...

, providing the equivalent of corresponding view camera

View camera

The view camera is a type of camera first developed in the era of the Daguerreotype and still in use today, though with many refinements. It comprises a flexible bellows which forms a light-tight seal between two adjustable standards, one of which holds a lens, and the other a viewfinder or a...

movements. This movement of the lens allows adjusting the position of the subject in the image area without moving the camera back; it is often used to avoid convergence of parallel lines, such as when photographing a tall building. Lenses that provide only shift may be called shift lenses, while those which can also tilt may be called tilt-shift lenses. The terms PC and TS are also used by some manufacturers to refer to this type of lens.

Short-focus PC lens

Photographic lens

A camera lens 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.While in principle a simple convex lens will suffice, in...

es (i.e., 17 mm through 35 mm) are used mostly in architectural photography; longer focal lengths may also be used in other applications such as landscape, product, and closeup photography. PC lenses are generally designed for single-lens reflex (SLR) cameras, as rangefinder cameras do not allow the photographer to directly view the effect of the lens, and view cameras allow for perspective control

Perspective control

Perspective control is a procedure for composing or editing photographs to better conform with the commonly accepted distortions in constructed perspective. The control would:...

using camera movements.

A PC lens has a larger image circle

Image circle

The image circle, or circle of illumination, of a lens is the circular area in the image plane formed by the cone of light transmitted by the lens . Within this circle is the smaller circle for which image definition is acceptable, the circle of good definition ; however, some authors make no...

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 image area cannot be shifted outside of the image circle. However, many PC lenses require a small aperture

Aperture

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 rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...

setting to prevent vignetting

Vignetting

In photography and optics, vignetting is a reduction of an image's brightness or saturation at the periphery compared to the image center. The word vignette, from the same root as vine, originally referred to a decorative border in a book. Later, the word came to be used for a photographic...

when significant shifts are employed. PC lenses for 35 mm cameras typically offer a maximum shift of 11 mm; some newer models offer a maximum shift of 12 mm.

The first PC lens manufactured for an SLR camera in any format was Nikon’s 1961 3.5 35 mm PC-Nikkor; it was followed by an 2.8 35 mm PC-Nikkor (1968), an 4 28 mm PC-Nikkor (1975), and an 3.5 28 mm PC-Nikkor (1981). In 1973, Canon introduced a lens, the TS 35 mm 2.8 SSC,
with tilt as well as shift functions.
Other manufacturers, including Olympus

Olympus Corporation

is a Japan-based manufacturer of optics and reprography products. Olympus was established on 12 October 1919, initially specializing in microscope and thermometer businesses. Its global headquarters are in Shinjuku, Tokyo, Japan, while its USA operations are based in Center Valley, Pennsylvania,...

, Pentax

Pentax

Pentax is a brand name used by Hoya Corporation for its medical-related products & services and Pentax Ricoh Imaging Company for cameras, sport optics , etc. Hoya purchased and merged with the Japanese optics company on March 31, 2008. Hoya's Pentax imaging business was sold to Ricoh Company, Ltd...

, Schneider Kreuznach

Schneider Kreuznach

Schneider Kreuznach is the abbreviated name of the company Jos. Schneider Optische Werke GmbH, which is sometimes also simply referred to as Schneider. They are a manufacturer of industrial and photographic optics....

(produced as well for Leica), and Minolta

Minolta

Minolta Co., Ltd. was a Japanese worldwide manufacturer of cameras, camera accessories, photocopiers, fax machines, and laser printers. Minolta was founded in Osaka, Japan, in 1928 as . It is perhaps best known for making the first integrated autofocus 35mm SLR camera system...

, made their own versions of PC lenses. Olympus produced 35 mm and 24 mm shift lenses. Canon currently offers 17 mm, 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.

Shape control

When the camera back is parallel to a planar subject (such as the front of a building), all points in the subject are at the same distance from the camera, and are recorded at the same magnification. The shape of the subject is recorded without distortion. When the image plane is not parallel to the subject, as when pointing the camera up at a tall building, parts of the subject are at varying distances from the camera; the more distant parts are recorded at lesser magnification, causing the convergence of parallel lines.
Because the subject is at an angle to the camera, it is also foreshortened.

When the camera back is not parallel to a planar subject, it is not possible to have the entire subject in focus without the use of tilt or swing; consequently, the image must rely on the depth of field

Depth of field

In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...

to have the entire subject rendered acceptably sharp.

With a PC lens, the camera back can be kept parallel to the subject while the lens is moved to achieve the desired positioning of the subject in the image area. All points in the subject remain at the same distance from the camera, and the subject shape is preserved. If desired, the camera back can be rotated away from parallel to the subject, to allow some convergence of parallel lines or even to increase the convergence. Again, the position of the subject in the image area is adjusted by moving the lens.

Applications

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 (b). 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 (a). With a perspective control lens, however, the lens may be shifted upwards in relation to the image area, 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.

The Arri

Arri

-History:Arri was founded in Munich, Germany as Arnold & Richter Cine Technik in 1917, named after founders August Arnold and Robert Richter. They produce professional motion picture equipment, digital and film cameras and cinematic lighting equipment...

motion-picture camera company offers a shift and tilt bellows system that provides movements for PL-mount lenses on motion-picture cameras.

Canon currently offers four lenses with tilt and shift functions: the TS-E 17 mm 4

Canon TS-E 17mm lens

The Canon TS-E 17 mm 4L is a tilt-shift, ultra-wide-angle prime lens that provides the equivalent of the corresponding view camera front movements on Canon EOS camera bodies...

, the TS-E 24 mm 3.5L II, the TS-E 45 mm 2.8, and the TS-E 90 mm 2.8. On the 45 mm and 90 mm 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.
The 17 mm and the 24 mm version II lenses allow independent rotation of the tilt and shift movements. The 90 mm lens gives 0.29 magnification, making it usable for moderate close-up work. All four lenses provide automatic aperture control.

Hartblei

Hartblei

Hartblei is a Ukrainian manufacturer of optical equipment for photography based in Kiev. They are primarily known for producing tilt-shift lenses . Taking lens designs produced by Kiev-Arsenal they modify these into tilt and shift designs of their own...

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 2.8, the TS-PC Hartblei 65 mm 3.5, the TS-PC Hartblei 80 mm 2.8, and the TS-PC Hartblei 120 mm 2.8. It also offers the TS-PC Hartblei 45 mm 3.5 to fit several medium-format camera bodies. The tilt and shift movements can be independently rotated in any direction.

Hasselblad

Hasselblad

Victor Hasselblad AB is a Swedish manufacturer of medium-format cameras and photographic equipment based in Gothenburg, Sweden.The company is best known for the medium-format cameras it has produced since World War II....

offers a tilt-and-shift adapter, the HTS 1.5, for use with the HCD 28 mm 4, HC 35 mm 3.5, HC 50 mm 3.5, HC 80 mm 2.8 and HC 100 mm 2.2 lenses on 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.
On September 22, 2008, Leica announced a 30 mm tilt-and-shift lens for its new S-System of digital SLRs.

Nikon

, also known as just Nikon, is a multinational corporation headquartered in Tokyo, Japan, specializing in optics and imaging. Its products include cameras, binoculars, microscopes, measurement instruments, and the steppers used in the photolithography steps of semiconductor fabrication, of which...

currently offers three PC lenses, all of which feature tilt and shift functions: PC-E Nikkor 24 mm 3.5D ED, PC-E Micro-Nikkor 45 mm 2.8D ED, and PC-E Micro Nikkor 85 mm 2.8D ED. The 45 mm and 85 mm “Micro” lenses offer close focus (0.5 magnification) for macrophotography. The PC-E lenses offer automatic aperture control with the Nikon D3

Nikon D3

The Nikon D3 is a 12.1 megapixel professional grade full frame digital single lens reflex camera announced by the Nikon Corporation on 23 August 2007 along with the Nikon D300 DX format camera. The D3, along with the Nikon D3X, was a flagship model in Nikon's line of DSLRs, superseding the D2Hs...

, D300

Nikon D300

The Nikon D300 is a 12.3-megapixel professional DX format digital single-lens reflex camera that Nikon Corporation announced on 23 August 2007 along with the Nikon D3 FX format camera. It replaced the D200 as Nikon's DX format flagship DSLR...

, and D700

Nikon D700

The Nikon D700 is a professional grade full-frame digital single-lens reflex camera introduced by the Nikon Corporation in July 2008 and manufactured in Japan. It uses the same 12.1 megapixel "FX" CMOS image sensor as the Nikon D3, and is Nikon's second full-frame digital SLR camera...

cameras. With some earlier camera models, a PC-E lens operates like a regular Nikon PC (non-E) lens, with preset aperture control by means of a pushbutton; with other earlier models, no aperture control is provided, and the lens is not usable.
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.

Schneider-Kreuznach offers the PC-Super Angulon 28 mm 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.

The Sinar

Sinar

Sinar AG is a Swiss company producing medium format and large format cameras.The name SINAR is explained as an acronym for "Studio, Industrie, Natur, Architektur, Reproduktion", though in , the acronym is explained as "Sach-, Industrie-, Natur-, undArchitekturfotografie sowie Reproduktion"...

arTec camera offers tilt and shift with the full range of Sinaron digital lenses.

All perspective control and tilt/shift lenses are manual-focus

Manual focus

In the field of photography, a manual focus camera is one in which the operator has to adjust the focus of the lens by hand. Before the advent of autofocus, all cameras had manually adjusted focusing; thus, the term is a retronym....

prime lens

Prime lens

In film and photography, a prime lens is either a photographic lens whose focal length is fixed, as opposed to a zoom lens, or it is the primary lens in a combination lens system....

es; most are quite expensive compared to regular prime lenses. Some medium format camera makers, such as Mamiya

Mamiya

is a Japanese company that today 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...

, have addressed this problem by offering shift adapters that work with the maker’s other prime lenses.

Aperture control

Most SLR cameras 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. For perspective-control and tilt/shift lenses, the mechanical linkage is impractical, and automatic aperture control was not offered on the first such lenses. Many PC and TS lenses incorporated a feature known as a “preset” aperture, 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. Although slightly easier than stopped-down metering, operation is less convenient than automatic operation.

When Canon introduced its EOS

Canon EOS

The Canon EOS autofocus 35 mm film and digital SLR camera system was introduced in 1987 with the Canon EOS 650 and is still in production as Canon's current DSLR system...

line of cameras in 1987, the
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

Nikon D300

, D3

Nikon D3

, and D700

Nikon D700

cameras. With some earlier cameras, the
lenses offer preset aperture control by means of a pushbutton that
controls the electromagnetic diaphragm; with other earlier cameras, no aperture control is provided, and the lenses are not usable.

Perspective control in software

Computer software (such as Photoshop's perspective and distort functions) can be used to control perspective effects in post-production

Post-production

Post-production is part of filmmaking and the video production process. It occurs in the making of motion pictures, television programs, radio programs, advertising, audio recordings, photography, and digital art...

. However, this technique does not allow the recovery of lost resolution in the more distant areas of the subject, or the recovery of lost depth of field

Depth of field

In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...

due to the angle of the film/sensor plane to the subject. Areas of the image which are enlarged by these digital techniques may suffer from the visual effects of pixel interpolation

Interpolation

In the mathematical field of numerical analysis, interpolation is a method of constructing new data points within the range of a discrete set of known data points....

, depending on the original image resolution, degree of manipulation, print/display size, and viewing distance.

The effect of using tilt or swing movements is less easily accomplished in post-production. If every part of the image is within the depth of field, it is fairly easy to simulate the effect of shallow depth of field that could be achieved by using tilt or swing;
however, if the image has a finite depth of field, post-production cannot simulate the sharpness that could be achieved by using tilt or swing to maximize the region of sharpness.

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