Tilt-shift Photography

On a view camera, the tilt and shift movements are inherent in the camera, and many view cameras allow a considerable range of adjustment of both the lens and the camera back. Applying movements on a small- or medium-format camera usually requires a tilt-shift lens or perspective control lens. The former allows tilt, shift, or both; the latter allows only shift. With a tilt-shift lens, adjustments are available only for the lens, and the range is usually more limited.
Tilt-shift and perspective-control lenses are available for many SLR cameras, but most are far more expensive than comparable lenses without movements. The Lensbaby SLR lens is a low-cost alternative for providing tilt and swing for many SLR cameras, although the effect is somewhat different from that of the lenses just described. Because of the simple optical design, there is significant curvature of field, and sharp focus is limited to a region near the lens axis. Consequently, the Lensbaby's primary application is selective focus and "toy camera"–style photography.
It is also possible to construct a tilt-shift lens of sorts, as described in the linked article by Dennison Bertram.