Saturday, 29 March 2014

Perspective Control A.K.A Tilt Shift Lenses

Tilt-shift lenses provide the DSLR shooter with a limited amount of functionality of a view camera. With a tilt shift lens mounted on a DSLR camera it could do all the movements that the front standard of a view camera could do although the rear standard (image sensor) remains fixed. Thus allowing some creative control over perspective and depth of field. Many optical tricks performed by the tilt shift lens could not be faked in post production and so they are indispensable for some advanced work mainly in architecture, landscape and product photography.

tilt shift lens
tilt shift lens: image courtesy wikipedia

Tilt and Shift Movements an Overview

Before discussing tilt and shift movements it should be understood that a tilt shift lens produces a much larger image circle than conventional lenses.

With a fixed lens mounted on a DSLR camera the lens plane, sensor plane and the plane of focus are all parallel to each other at all times. Tilt movements allow the photographer to tilt the plane of focus such that it is no longer perpendicular to the lens axis, thus creating a wedge shaped depth of field. The width of the wedge increases as the distance from the camera increases. In effect tilting the lens does not increase depth of field instead it allows the photographer to modify it to suit the subject being photographed.

Shifting the lens changes the lens's imaging circle in relation to the sensor and thus uses only a small crop from the image circle, from which portion of the image circle should the image be formed is determined by the direction of the shift.

Advantages of Tilt Shift Lenses

Tilt shift lenses offer many advantages, like rendering straight lines straight in images, correct the geometric distortion in objects that are in the foreground when shooting with a wide angle lens, helps photograph a mirror without the camera being reflected in it etc. We have covered all these in detail in previous articles. But one thing worth mentioning is that  even when unshifted, a tilt shift lens will produce better image quality at the edges of the frame when compared to fixed lenses. This is similar to the effect of using lenses designed for full frame cameras on crop sensor bodies.  Due to the crop factor the camera only uses a crop from the center portion of the lens and thus image softness, vignetting, distortion etc are minimized. These defects are generally more pronounced at the edges of the lens and by not using the corners of the lens all the problems areas are simply cropped out.

Disadvantages of Tilt Shift Lenses

Although advantages far outweigh their disadvantages, tilt shift lenses do have their share of disadvantages.

  1. In most cases they are prohibitively expensive.
  2. They are limited in the amount of movement possible.
  3. They are single focal length lenses and you will need individual lenses of different focal length if you need to cover many focal lengths. (In case of view cameras as the movements were integral to the camera body they allowed movements with lenses of all focal lengths).
  4. Tilt shift lenses are often much larger and heavier than their fixed counterparts of the same focal length and maximum aperture.

Here are the tilt shift lenses currently available in the market from popular camera manufacturers

Tilt shift lenses from Canon

Canon TS-E 17mm f/4L Tilt-Shift Lens

Canon TS-E 24mm f/3.5L II Tilt-Shift Lens

Canon TS-E 45mm f/2.8 Tilt-Shift Lens

Canon TS-E 90mm f/2.8 Tilt-Shift Lens