Tilt–shift photography

Tilt-shift photography is an artistic technique where the lens is tilted and shifted relative to the attached camera. Traditionally, the two are connected by a bellows. When tilt is applied, the film or image sensor is not at a right angle to the optical axis of the lens, causing a gradient of focus. This effect can be used to direct the viewer's gaze by blurring parts of the image the photographer wishes to de-emphasize, or can be used to simulate a smaller depth of field by bringing the foreground and/or background out of focus. It can also correct for perspective, by sharpening the focus of a foreground and background that would otherwise be outside the depth of field; in theory, perfect perspective correction happens when the planes of the lens, the image sensor, and the object being imaged all intersect. [1] One builder of a do-it-yourself tilt-shift lens noted that the lens used should be one intended for a larger film format than the camera, so that vignetting doesn't occur as the lens is tilted [2].

A collection of links to galleries and information on tilt-shift photography can be found here [3].