Depth of field of the lens tilt/shift
Online calculator for lens depth of field uses the focal length of the lens, tilt angle, and focusing distance without tilt to determine the position of the plane of maximum sharp focus and depth of field:
«Focusing distance without rotation» corresponds to (approximately) applied to the focus ring. Pay attention to how small changes in the rotation angle lead to large changes in the tilt angle of the focal plane, and how the effect of the rotation angle decreases with its increase. Notice also how the focusing distance without rotation can greatly influence the tilt angle of the focal plane. Similarly to the usual depth of field, the total angular depth of field (difference between the near and far angles of acceptable sharpness) decreases with a decrease in the focusing distance.