Of lenses: To reorient in relationship to the image sensor. This allows the pictures to be taken at with the lens at an angle while keeping the focal plane parallel to the object being photographed, reducing the effects of perspective or allowing photographs of mirrors without the photographer appearing in the reflection. If a lens supports rotation in both the horizontal and vertical planes, the action of rotating the lens in the vertical plane is referred to as “shift”, the action of rotating the lens in the horizontal plane as “tilt”.