Tilt-shift photography
"
Tilt-shift photography" refers to the use of
camera movements on small- and medium-format cameras, and sometimes specifically refers to the use of tilt for
selective focus, often for simulating a
miniature scene. Sometimes the term is used when the shallow
depth of field is simulated with digital postprocessing; the name may derive from the
tilt-shift lens normally required when the effect is produced optically.
"Tilt-shift" actually encompasses two different types of movements: rotation of the
lens plane relative to the
image plane, called
tilt, and movement of the lens parallel to the image plane, called
shift. Tilt is used to control the orientation of the plane of focus (PoF), and hence the part of an image that appears sharp; it makes use of the
Scheimpflug principle. Shift is used to adjust the position of the subject in the image area without moving the camera back; this is often helpful in avoiding the convergence of parallel lines, as when photographing tall buildings.
History and use
Movements have been available on
view cameras since the early days of photography; they have been available on smaller-format cameras since the early 1960s, usually by means of special lenses or adapters.
Nikon introduced a lens providing shift movements for their 35 mm
SLR cameras in 1962,
[1] and
Canon introduced a lens that provided both tilt and shift movements in 1973;
[2] many other manufacturers soon followed suit.
Canon and Nikon each currently offer several lenses that provide both movements. Such lenses are frequently used in architectural photography to control perspective, and in landscape photography to get an entire scene sharp.
Some photographers have popularized the use of tilt for
selective focus in applications such as portrait photography. The selective focus that can be achieved by tilting the plane of focus is often compelling because the effect is different from that to which many viewers have become accustomed.
Walter Iooss Jr. of
Sports Illustrated,
Vincent Laforet, Ben Thomas, and many other photographers have images using this technique on their web sites.
Camera movements
Tilt
24 mm lens that tilts (as seen above) as well as shifts
A camera lens can provide sharp focus on only a single plane. Without tilt, the image plane (containing the film or
image sensor), the lens plane, and the plane of focus are parallel, and are perpendicular to the lens axis; objects in sharp focus are all at the same distance from the camera. When the lens plane is tilted relative to the image plane, the plane of focus (PoF) is at an angle to the image plane, and objects at different distances from the camera can all be sharply focused if they lie in the same plane. With the lens tilted, the image plane, lens plane, and PoF intersect at a common line;
[3][4] this behavior has become known as the
Scheimpflug principle. When focus is adjusted with a tilted lens, the PoF rotates about an axis at the intersection of the lens's front focal plane and a plane through the center of the lens parallel to the image plane; the tilt determines the distance from the axis of rotation to the center of the lens, and the focus determines the angle of the PoF with the image plane. In combination, the tilt and focus determine the position of the PoF.
Using tilt changes the shape of the depth of field (DoF). When the lens and image planes are parallel, the DoF extends between parallel planes on either side of the PoF. With tilt or swing, the DoF is wedge shaped, with the apex of the wedge near the camera, as shown in
Figure 5 in the Scheimpflug principle article. The DoF is zero at the apex, remains shallow at the edge of the lens's field of view, and increases with distance from the camera. For a given position of the PoF, the angle between the planes that define the near and far limits of DoF (i.e., the angular DoF) increases with lens
f-number; for a given
f-number and angle of the PoF, the angular DoF decreases with increasing tilt. When it is desired to have an entire scene sharp, as in landscape photography, the best results are often achieved with a relatively small amount of tilt. When the objective is
selective focus, a large amount of tilt can be used to give a very small angular DoF; however, the tilt fixes the position of the PoF rotation axis, so if tilt is used to control the DoF, it may not be possible to also have the PoF pass through all desired points.
View camera users usually distinguish between rotating the lens about a horizontal axis (tilt), and rotation about a vertical axis (
swing); small- and medium-format camera users often refer to either rotation as "tilt".
In a subject plane parallel to the image plane, parallel lines in the subject remain parallel in the image. If the image plane is not parallel to the subject, as when pointing a camera up to photograph a tall building, parallel lines converge, and the result sometimes appears unnatural, such as a building that appears to be leaning backwards.
Shift is a displacement of the lens parallel to the image plane that allows adjusting the position of the subject in the image area without moving the camera back; in effect the camera can be aimed with the shift movement.
[5] Shift can be used to keep the image plane (and thus focus) parallel to the subject; it can be used to photograph a tall building while keeping the sides of the building parallel. The lens can also be shifted in the opposite direction and the camera tilted up to accentuate the convergence for artistic effect.
Shifting a lens allows different portions of the
image circle to be cast onto the image plane, similar to cropping an area along the edge of an image.
Again, view camera users usually distinguish between vertical movements (
rise and
fall) and lateral movements (shift or
cross), while small- and medium-format users often refer to both types of movements as "shift".
[edit] Lens image circle
Whereas the image circle of a standard lens usually just covers the image frame, a lens that provides tilt or shift must allow for displacement of the lens axis from the center of the image frame, and consequently requires a larger image circle than a standard lens of the same focal length.
[edit] Applying camera movements
Use of lens shift to
control distortion
On a view camera, the tilt and shift movements are inherent in the camera, and many view cameras allow a considerable range of adjustment of both the lens and the camera back. Applying movements on a small- or medium-format camera usually requires a
tilt-shift lens or
perspective control lens. The former allows tilt, shift, or both; the latter allows only shift. With a tilt-shift lens, adjustments are available only for the lens, and the range is usually more limited.
Tilt-shift and perspective-control lenses are available for many SLR cameras, but most are far more expensive than comparable lenses without movements. The
Lensbaby SLR lens is a low-cost alternative for providing tilt and swing for many SLR cameras, although the effect is somewhat different from that of the lenses just described. Because of the simple optical design, there is significant
curvature of field,
[6] and sharp focus is limited to a region near the lens axis. Consequently, the Lensbaby's primary application is selective focus and "toy camera"–style photography.
It is also possible to construct a tilt-shift lens of sorts, as described in the linked article by Dennison Bertram.
[edit] Selective focus
Selective focus can be used to direct the viewer's attention to a small part of the image while de-emphasizing other parts.
With tilt, the effect is different from that obtained by using a large
f-number without tilt. With a regular camera, the PoF and the DoF are perpendicular to the line of sight; with tilt, the PoF can be almost parallel to the line of sight, and the DoF can be very narrow but extend to infinity. Thus parts of a scene at greatly different distances from the camera can be rendered sharp, and selective focus can be given to different parts of a scene at the same distance from the camera.
[7]
With tilt, the
depth of field is
wedge shaped. As noted above under
Tilt, using a large amount of tilt and a small
f-number gives a small angular DoF. This can be useful if the objective is to provide selective focus to different objects at essentially the same distance from the camera. But in many cases, effective use of tilt for selective focus requires a careful choice of what is sharp as well as what is unsharp, as Vincent Laforet has noted.
[8] Because the tilt also affects the position of the PoF, it may not be possible to use a large amount of tilt and have the PoF pass through all desired points. This may not be a problem if only one point is to be sharp; for example, if it is desired to emphasize one building in a row of buildings, the tilt and
f-number can be used to control the width of the sharp area, and the focus used to determine which building is sharp. But if it is desired to have two or more points sharp (for example, two people at different distances from the camera), the PoF must include both points, and it usually is not possible to achieve this while also using the tilt to control DoF.
Selective focus using tilt appears in motion pictures such as
Minority Report, (2002). Director of photography
Janusz Kamiński says he prefers using tilt-shift lenses to digital post-production as too much digital can detract and "It doesn’t look organic."
[9]
[edit] Miniature faking
Miniature simulation using digital postprocessing
Selective focus via tilt is often used to simulate a miniature scene,
[10][11] though as noted above, the effect is somewhat different from the shallow DoF in
close-up photography of miniature subjects.
[12] Many such images are described as employing "tilt-shift", but the term is something of a misnomer because shift is seldom involved and is usually unrelated to the effect produced. The term may derive from the
tilt-shift lens normally required when the effect is produced optically.
Basic
digital postprocessing techniques can give results similar to those achieved with tilt, and afford greater flexibility, such as choosing the region that is sharp and the amount of blur for the unsharp regions. Moreover, these choices can be made after the photograph is taken. One advanced technique,
Smallgantics, is used for motion-pictures; it was first seen in the 2006
Thom Yorke music video
Harrowdown Hill, directed by
Chel White. Artist
Olivo Barbieri is well known for his miniature-faking stills in the 1990s.
Focus mode