Scheimpflug principle
The entire subject plane is in focus if the lens plane is inclined downward and the extended lines from the lens plane, the object plane, and the film plane all connect at the same location, according to Theodor Scheimpflug (1865–1911). When using tilt-shift lenses or tilt-and-swing movements on view cameras, this technique is put into use. Accordingly, if you're taking a landscape snap, you can tilt the lens forward until the plane of focus is parallel to the ground. As a result, even while shooting with the lens wide open, depth of field is greatly expanded.
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