Tilt–shift photography is the use of camera movements that change the orientation or position of the lens with respect to the film or image sensor on cameras.
Sometimes the term is used when a large depth of field is simulated with digital post-processing; the name may derive from a perspective control lens (or tilt–shift lens) normally required when the effect is produced optically.
"Tilt–shift" 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.
Tilt shift lenses enable is to transcend the normal restrictions of depth of field and perspective. Many of the optical tricks these lenses permit could not otherwise be reproduced digitally—making them a must for certain landscape, architectural and product photography and of course as a creative tool.
Shift movements shift the location of the lens's imaging circle relative to the digital camera sensor. This means that the lens's center of perspective no longer corresponds the the image's center of perspective, and produces an effect similar to only using a crop from the side of a correspondingly wider angle lens.
Tilt movements tilt the plane of sharpest focus so that it no longer lies perpendicular to the lens axis. This produces a wedge-shaped depth of field whose width increases farther from the camera. The tilt effect therefore does not necessarily increase depth of field—it just allows the photographer to customise its location to better suit their subject matter.