Tilting the Lens
When the lens is not tilted, the plane of focus remains parallel with the camera’s sensing plane. Tilting the lens tilts the plane of focus. The effect is that objects at different distances from the camera can all be in focus at once. Tilting the plane of focus the other way can result in radically defocusing some objects in the scene.
By angling the lens, the plane of focus is angled in the same direction to a greater degree. The rotation of the plane of focus is described by the Scheimpflug principle.
By tilting the lens, the photographer can obtain sharp focus over a whole plane that is not a constant distance from the camera. Tilting the opposite way allows the photographer to obtain the miniature effect in which the top and bottom of the frame are highly blurred which simulates the blur present in macro photographs.
More things in focus
In this example, I obtain focus on objects that are different distances from the camera. In this scene, there is sheet music on the right that is in focus. The music is closest to the camera. The rubber plant is second farthest from the camera, but is out of focus. The monster plant is farthest away from the lens, but it is in clear focus. How did i obtain clear focus on the nearest and farthest subject, but not the middle depth subject? I tilted the lens to the right so that the plane of focus rotated to the right about a vertical axis. The altered plane of focus intersects the music and the monstera plant, but not the rubber tree on the left.
Scene of my living room with focus on foreground music stand and middle plant in background accomplished by tilting lens to the right. Canon TS-E 24mm F/3.5L
Fewer things in focus
The camera stayed on its tripod for this shot, so nothing about the scene has changed since the previous shot. The difference is that I tilted lens to the left. This made the plane of focus intersect only the monstera plane. This puts the sheet music and the rubber tree out of focus. The focal plane has rotated to the left.
Scene of my living room with middle plant in focus and other subjects defocused by tilting lens to the left. Canon TS-E 24mm F/3.5L
Miniature Effect
Tilting the lens up or down can be used to achieve a miniature effect. Looking at small objects with high magnification results in very this depth of field. So, when we see object in focus and foreground and back ground out of focus, we associate this with high magnification of a very small subject. When the lens is tilted up or down to achieve a thin strip of focus on the subject and radical defocus of foreground and background, it can appear that the subject is miniature when it is not. In my example above, I have not achieved this. It is typically easier to achieve this with a 50mm tilting lens compared to the 24mm tilt-shift lens that I have used.
