What is the specific function of shifting lens?

Axis-shifting lens refers to a lens that adjusts the viewing angle by moving the optical axis of the lens.

The function of the shift lens is not only to correct the perspective deformation, but also to adjust the focal plane position. In general, the focal plane of the camera is parallel to the film plane, and the scene in the focal plane is clear and the Jiao Wai is blurred when shooting with large aperture; If the focal plane is adjusted by moving the axis lens, the sharpness can be changed. Obviously, shifting lens is most suitable for architecture, landscape and commercial photography.