Applications and Examples
Tilt and shift lenses certainly aren't the kind of equipment that most photographers will be able to afford or justify, indeed many may well question their continued existence given that their capabilities can be imitated using software. But the key here is that word 'imitated'; for critical applications which require the highest quality, the use of movements gives superior results. This is nothing new - indeed it's long been a staple technique for photographers using large-format cameras - but in the context of modern digital capture it becomes important when trying to extract the maximum possible image quality from the latest round of high-resolution DSLRs.
The purpose of such lenses is two-fold. Firstly, shift movements are used to help control perspective, and most famously avoid the 'converging verticals' effect commonly seen when shooting architecture with wide angle lenses. This can of course be easily corrected using software (e.g. Photoshop's 'Lens Correction' filter), but such methods work by stretching parts of the image, and lose resolution in the process; in contrast the use of shift movements maintains critical detail from corner to corner.
Secondly, tilt movements are used as a means of controlling depth of field. Most notably, this allows the user to achieve extended depth of field without having to stop down to small apertures, and therefore avoids the associated penalty of image softening due to diffraction. However tilt movements can also be used to manipulate the direction of the plane of focus across an image for creative effect; perhaps the currently most fashionable application is to use shallow depth of field to make real-life images look like miniature models.
Shooting with a tilt and shift lens is an exercise in painstaking technique and patience. Visualizing the effect of shift on geometry is relatively simple, but using tilt to manipulate the plane of focus is a lot more complicated; ideally you need a camera with a highly functional live view system that allows you to check fine focus critically across the frame. Setting exposure is not entirely strightforward either - tilting or shifting the lens will confuse the camera's meter, so it's best to work in manual, check your histogram regularly, and shoot RAW for maximum leeway.
In this section we're going to explore a few of the possible applications of a tilt and shift lens, and how well the Hartblei delivers them (it's not however intended to be an exhaustive tutorial on the use of lens movements). The example images have been slightly rotated and scaled for best overlay (so as to illustrate the point most clearly) and then cropped. Full size versions of some of these images can be downloaded by clicking on the captions.
Perspective correction using shift movements
Probably the first application most people will think of in connection with a tilt and shift lens is the correction of converging verticals. This can make a big difference when using a wideangle lens to shoot architecture, but as the focal length increases, the effect becomes progressively more subtle. The example below shows the difference between shooting normally and with maximum downwards shift, at close to the lens's minimum focus distance. The application of shift has improved the overall geometry slightly, but it's fair to say that with this 120mm lens the effect is very minor.
With maximum shift (10mm)
The application of shift can have a second function though - it allows the camera back to angled closer to parallel with any desired plane of focus on the subject, and therefore give more even sharpness especially at larger apertures.
Depth of field control using tilt movements
While shift movements have limited effect with this relatively long lens, the corollary of this is that the use of tilt movements to manipulate depth of field becomes extremely effective, and most relevant to its intended use. To illustrate this, here are comparison shots using the lens with and without tilt applied. The camera is looking down at the figure from an angle of about 45 degrees, and to exaggerate the effect we're shooting at F4 (normally you'd shoot at smaller apertures for maximum sharpness and a little more depth of field).
In the first shot with the lens pointing straight ahead, only the face is in focus. We can bring more of the front of the figure into focus by tilting the lens upwards; at maximum tilt almost all is in focus. What is happening here is perhaps easiest to understand when you consider that prime lenses often focus closer by moving the lens further away from the sensor; tilting the lens simply means that the part of the lens which is further away from the sensor is effectively focusing closer. The practical upshot of this is that the plane of sharp focus is no longer parallel with the sensor, but instead the focus distance varies across the frame. This in essence is the raison d'etre of a tilt lens - you can extend the apparent depth of field without stopping down and degrading the image through diffraction.
With maximum tilt (8 degrees)
In practice, visualizing the effect of tilt on the final image isn't straightforward. It's more or less impossible to judge the position of the plane of focus sufficiently accurately using even the best DSLR viewfinder, and this is therefore one application for which the studio-friendly live view systems of Canon and Nikon's latest models become a real benefit. Of course it's still advisable to check the final shots on a computer whenever possible before calling it a day on the shoot.
Combining shift with tilt
The example below illustrates much the same principle, but adds an additional shift step for further correction. Again we've used F4 to illustrate the effect most clearly. In this setup, the subject is at an angle of approximately 45 degrees to the taking camera (Nikon D3X), and approximately 30cm / 12" below it to give a slightly overhead view.
With the lens pointing straight, depth of field is very narrow, and only the 'Fujifilm' badge on the F200 EXR is in focus. Tilt the lens fully to the left and recompose, and almost the entire front of the camera now comes within depth of field - a dramatic improvement. Adding maximum downwards shift improves matters further - the shape of the camera is rendered better, and sharpness is slightly more consistent across its front face (as the focus plane is nearer to being properly parallel with the camera) - but the effect is quite subtle.
Using tilt for selective focus
Tilting the lens can also be used to focus selectively on a specific element in an image. In the sample below, the application of 4 degrees of tilt to the right allows the red players at the left and right of the frame to be thrown out of focus, despite being at the same distance from the camera as the one in the centre of the frame. This approach can also be used to blur a relatively close background beyond what could normally be achieved.
Tilt movements may also be used to give real-life scenes the appearance of miniature models. This effect is a result of the angled focus plane giving unexpected transitions between in-focus and out-of-focus regions which resemble the shallow depth of field effects of close-up photography. The most familiar perspective for such shots tends to be looking down on a scene from a height, but naturally other approaches also work. In the example below, the miniaturisation effect comes primarily from the unusual focus transitions on the flowers in the hanging basket.
Panoramas and composites
One less-appreciated application for shift lenses is that of panorama shooting. The method is simplicity itself; mount the camera on a tripod, and make two exposures, one with the lens fully shifted to the left, another with the lens fully shifted to the right. In principle the two images should align near-perfectly, and give a seamless panorama with just minimal masking work required.
The example below illustrates this in practice. In this particular case the two images align extremely well, with just a few pixels vertical offset - an indication of the precision of Hartblei's rotation mechanism. A little masking is needed to deal with elements which move between the two exposures - the clouds, and the boat at the bottom of the image - but overall this must count as one of the most painless methods of making panoramas. These images were shot at an aperture of F8 using magnified live view to focus, and image quality is extremely impressive right across the frame, although with a little visible loss of sharpness at the extreme corners.
Note also that this approach can easily be extended in various fashions, for example to making 2 row / 2 column composites. When using this method to construct panoramas and composites, ideally the position of the lens's entrance pupil should be kept constant and the camera rotated relative to it; otherwise the slight change in perspective may cause problems with objects near to the camera. For this purpose, Hartblei's widest lens, the 40mm F4 TS, comes with an integrated tripod mounting collar.