A Tilt-Shift Perspective
13/07/11We have been using the new Canon 24mm f3.5 Tilt-shift (TS-E) lens now for the last couple of months for both cityscape and landscape photography and thought we should post a mini-review. We considered the images we like to shoot and the most appropriate TS-E lens, and eventually chose the 24mm. Although the 17mm f4.0 lens would probably suit our style more with its wider perspective, the inability of the 17mm to take filters due to its bulbous front element was a major negative. We use NDs and graduated NDs extensively and the 24mm has no problems with external filter holders. The limitations of the 24mm can be worked around by using a full frame camera and utilising the shift panorama if a wider perspective is required.
Both TS-E lens are manual focus only and best used on a tripod, particularly when using the tilt function (to accurately determine the focus plane). However, both lens have autofocus confirmation via the appropriate AF point lighting up and sounding on the view finder.
A little first about the principles of tilt-shift lens. One reason why the image qualities of these lenses are so highly regarded is due to the huge image circle that it projects.
The new Canon TS-E lens projects a huge 67.2mm as opposed to the 43.2mm of most EF or full frame lenses. As a result they are very sharp even wide open, have very little fall off due to the large image circle, and there is little chromatic aberration or distortion. The 24mm is arguably the sharpest lens in the Canon line-up. The large image circle also allows a greater degree of shift (or moving the sensor around the image circle). Up to 12mm shift is available in any direction.
The Shift Function is relatively easy to understand and to use. The shift function shifts the image circle relative to the image sensor. For the first time in a TS-E lens, there is the capability of independent rotation of the tilt and shift axes relative to the camera and to each other. For us, the shift function is of most value in cityscape images, where correction of converging verticals may be desired. This allows the image plane to be maintained parallel to the subject plane. This diagram from Mark Evans highlights the principles:
This first image is taken by a conventional 16-35mm lens with a 24mm perspective. The camera is pointed up at the building and thus the image plane and subject plane are not parallel and the top of the building appears smaller.
The second image is taken by the 24mm TS-E lens, portrait format with a full +12mm shift. The image plane remains parallel to the subject plane, and by shifting the lens up, the entire building is captured.
The differing perspectives are obvious, and we feel each has their place.
In order to simulate a 17mm or wider perspective, it is relatively easy to stitch images to form a simple panorama using the shift function. As the lens projects an image circle that is much larger than the sensor, shifting allows the movement of the sensor from the centre of the image circle and capture a wider scene. The following vertical panoramic image combines three landscape format images by shifting the lens to the top, centre, and bottom (+12mm, 0mm and -12mm).
These were the three source images for the panorama
The tilt function may also be used in landscape photography. It’s primary role is to alter the plane of focus. With a normal lens, the image plane or sensor plane, the lens plane, and the plane of focus are parallel, and at 90 degrees to the lens axis. This means that subjects that are in sharp focus are at the same distance from the camera.
When the lens plane is tilted with respect to the image plane, the plane of focus is at an angle to the image plane, and objects at different distances from the camera can all be sharply focused as long as the lie in the same plane.
In Landscape Photography, the obvious application is to adjust the lens plane so that the image is sharp from front to back without using small apertures or high f-numbers. There are times when high f –numbers may not be desirable, and often the sweet spot for a lens is f8-f11. Using the tilt function on a TS-E lens to adjust the lens and focus plane so that it is near parallel to the ground allows the entire image to be sharp even at larger apertures. In this image the entire image is sharp at f3.5
Alternatively, one may want to adjust the focus plane so that it is very narrow, to produce a so called “fake miniature” effect. In our opinion this is a bit of a novelty, but it is still fun to achieve. This image reveals a very narrow focus plane, and I’ve included a larger version so this can be easily identified:
In summary then, the Tilt-shift lenses are a welcome addition to the landscape and cityscape photographer’s kit, and there are many more applications than we have discussed in this article. Interior architectural and design photography for example would be an ideal application of the 17mm TS-E lens. If nothing else, the 24mm TS-E f3.5 IIL is also a wonderful 24mm prime, but the tilt-shift functions adds a dimension to our photography that was not previously achievable in camera.