Perspective Control lenses (PC) can (shift up or down)
Perspective Control lenses (PC) have the capacity rise or fall (shift up or down) which lets a photographer arrange the outlook of the subject to gain additional control over what reaches the sensor or the film without being distorted. In addition to up and down travel, some also have the capability to tilt, which lets a film back or lens to tip at angles, in any direction. Tilting the lens angle in relation with the film plane or sensor adjusts the focus plane, although not the real view. This provides for greater field depth for scene where the primary subject may be stretched out in one dimension, although not another.
(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.
(c) Shifting the lens upwards results in a picture of the entire subject. perspective, control, perspective control, lens, control lens, pc, perspective control lens, lenses, shift, perspective control lenses, control lenses, tilt, nikon, pc perspective, distortion, pc perspective control, perspective control pc,
For example, one could photograph the length of a wall that's very long, but the photography does not need to capture much height. Without tilt capabilities, the photographer would have to stand far from the wall and be parallel to it—that is, the film and the lens planes are the same as the plane of the wall. As soon as you move towards one end of the wall, the angles of the film and lens planes become greater and greater, relative to the fixed position of the wall. In order to keep the entire wall in focus, the photographer must "stop down" by making the aperture smaller and smaller.
The smaller the hole in the lens, the more depth of field can be achieved, but there are limits to how far you can go. If you want to stand inches from the corner of the wall and capture the entire wall in focus, a normal lens may not be able to do the job because the aperture can't get small enough. But, the problem can be solved if the film or lens plane remains parallel to the wall, even though the camera itself might not be. Thus, by tilting the lens, you can adjust the plane of focus so that the entire length of the wall is in focus without moving the camera.
Lenses which can 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.
This type of lens is used mostly in architectural and other technical photography. Perspective control 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 correction using 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’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). In 1973,
Canon introduced a lens, the TS 35 mm f/2.8 SSC, with tilt as well as shift functions. Other manufacturers, including 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 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.
Example application of lens shift. The photographs, from left to right, correspond to diagrams (a), (b), and (c) above, respectively. The rightmost image employs a shift.
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 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.
Other application of shifting is in aerial photography with relatively large exposure time forced by poor light condition of scene. The higher V/H ratio (forward speed of aircraft to its height above ground level) with fixed exposure time results in more image blur in the picture. In this case shifting with the same amount of V/H will neglect the image motion effect.
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 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 five lenses with tilt and shift functions: the Canon TS-E 17mm f/4 lens, the TS-E 24 mm f/3.5L (version I and II), 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.
35 mm f/3.5 PC-Nikkor lens
2008 Nikkor f/3.5 24mm PC-E tilt-shift lens mounted on a Nikon D700 camera
The 24mm PC-E lens shown in its tilt mode
Nikon introduced the 35 mm f/3.5 PC-Nikkor lens in 1961. It was the first shift lens in the 35 mm format and shifts up to 11 mm in any direction. Nikon currently offers four “PC” lenses, all of which feature tilt and shift functions: PC-E Nikkor 24 mm f/3.5D ED, PC-E Micro-Nikkor 45 mm f/2.8D ED, PC-E Micro Nikkor 85 mm f/2.8D ED, and PC Micro-Nikkor 85 mm f/2.8D. The 45 mm and 85 mm “Micro” lenses offer close focus (0.5 magnification) for macro photography. The PC-E lenses offer automatic aperture control with the Nikon
D700 cameras. With 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. The PC Micro-Nikkor 85 mm f/2.8D lens offers only preset aperture control, actuated mechanically by pressing a plunger.
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.
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, HC 80 mm f/2.8 and HC 100 mm f/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.
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.
In 2008, Zenitar announced 35 mm f/2.8 and 80 mm f/2.8 tilt-and-shift lenses for Pentax K mount, but has been making M42 versions for years.
Introduced at Photokina 2008, the Sinar arTec camera offers tilt and shift with the full range of Sinaron digital lenses.
All perspective control and tilt/shift lenses are manual-focus prime lenses; most are quite expensive compared to regular prime lenses. Some medium format camera makers, such as Mamiya, have addressed this problem by offering shift adapters that work with the maker’s other prime lenses.
The first SLR cameras with internal (“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. 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, 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 EOS 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
D700 cameras; with earlier cameras, the lenses offer preset aperture control by means of a pushbutton that controls the electromagnetic diaphragm.
Perspective control in software
Main article: Perspective control
Computer software (such as Photoshop's perspective and distort functions) can be used to control perspective effects in post-production. 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 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, depending on the original image resolution, degree of manipulation, print/display size, and viewing distance.
Post-production cannot duplicate the effect of using tilt or swing movements on a tilt/shift lens.