Tilt Shift Lenses
When I first received my Canon 17mm T/S (tilt-shift) lens, numerous people asked what I would use it for. “Everything” I answered - I would use it with the Nude, landscape, architecture, and perhaps even flowers. This was often met with surprise, as the standard view is that tilt-shift lenses are most appropriate for architecture, but coming from a history of using large format film cameras, all of which have tilt and shift (in addition to numerous other camera movements) built in, for me it seemed obvious to use it wherever appropriate!
The 17mm T/S lens also works with the 1.4x and 2x teleconverters, providing two additional lenses (23.8mm and 34mm respectively). While the image quality does drop some with the addition of the teleconverters, the increased flexibility of the tilt-shift, combined with the fact that the 17mm is already incredibly sharp makes this feature a real bonus of the lens.
The Toy Effect
Probably the best known use of a tilt-shift lens on small cameras (as opposed to large format cameras), is to change how the plane of focus is treated in an image. This is commonly known as the Toy or Miniature effect, as the resulting image often looks like a photograph of a scale model, as opposed to the real world.
Control over the plane of focus is accomplished by tilting the lens away from being parallel to the camera; this forces the focus in the image to be asymmetrical, and therefore changes the way focus works. With this image of Vanessa, to focus it on her exclusively, I used a strong (6.5 degree) tilt, and then carefully focused on her face using the 100% magnification possible with a LiveView enabled camera. Due to the tilt (which as it is sideways, is technically called a swing), the focus runs quickly through the wall behind her, and the walls to her left and right are significantly out of focus.
Wide Angle Distortion
A real advantage of working with a tilt-shift lens is that it can help overcome some problems inherent in some kinds of lenses. With the 17mm T/S, this is most evident when the lens used to avoid distortion
In the example to the right, I wanted to compose an image with Vanessa at the extreme edge of the frame, but in order to get the composition I wanted, an ultra-wide (17mm on a 24x36mm/full frame sensor) lens was required. This created a great deal of distortion of her form, as is the case with objects close to an edge with a wide-angle lens (see the diagram below). Without resorting to advanced software techniques, there is no easy way to overcome this, unless a tilt-shift lens is used.\p>
Distortion Correction with a Shift
To avoid the distortion inherent in wide-angle lenses, it is necessary to keep the primary subject located directly in front of the lens; in some cases this can work fine, but it severely limits the compositional possibilities, unless a tilt-shift lens is used.
With a tilt-shift lens, once the subject is placed directly in front of the camera, the lens can be shifted to the side (or up or down) to change the composition, without altering the perspective (and there by, minimizing the distortion) of the main subject.