Tilt-shift lens

A tilt-shift lens, is a lens whose optical part can be tilted and moved. Simply put, it is a lens in which the optics can be tilted and / or shifted relative to the image sensor. The tilt and shift lenses also rotate to allow the lens to tilt and / or move in a wide range of directions.

What is the tilt function for?

The tilt function takes advantage of the Scheimpflug principle, which describes a situation in which the plane of the lens is no longer parallel to the plane of the image (or to the image sensor, in the case of digital). While this may seem dauntingly complex, the important point to remember is this: the tilt feature can dramatically alter your focus plane.

In a typical lens, the focus plane is parallel to the sensor. This means that if you focus on an object 2 meters away with a normal lens using a moderately wide aperture, everything from left to right will be in focus at your focus distance of 2 meters, with Areas in front of and behind the focus point gradually become blurred. However, tilting a lens left or right changes the focal plane from parallel to approaching perpendicular to the sensor, with the result that the focus plane passes through the frame vertically. This means that everything from the front to the back of the image can be brought into focus even using a moderately wide aperture, with the left and right areas of the focus area gradually becoming blurred.

___ Sensor plan

___ Lens plan

| | | Area of sharpness

Alternatively, by tilting the lens up or down, you can accentuate the effect of limited depth of field at a given aperture. This technique is used to make cities look like replicas of scale models when photographed from elevated perspectives.

What is the shift function for?

The shift function, as the name suggests, allows the lens optics to move relative to the image sensor. The key to this intriguing ability is that tilt and shift lenses are designed to project a much larger image circle than traditional lenses.

By moving a lens, you can simulate photographing your subject from a different camera position. By using the shift function, you can create architectural photos without converging vertical lines. To do this, the camera must be level and pointed directly at the building. The lens is then moved upward to include the top of the building and in some cases a significant amount of sky for optimal framing (thus sacrificing nearby foreground elements). Because the lens is leveled, the vertical lines do not converge. And because the lens is offset, the lens simulates the view of a camera placed much higher than it actually was.

O Image circle

One specific use of the offset feature is to allow camera angles that are otherwise not possible. For example if you want to photograph the reflection of a mirror as if you were in front of it, but without the camera being visible.