How Large Format Movements work
Tilt, swing, and the Scheimpflug rule for view cameras.
Where to find it
Tools tab Large Format Movements
Summary
Calculator for view-camera lens and back movements (tilt, swing). Computes the Scheimpflug hinge distance and the wedge of depth of field a tilted lens produces.
Detail
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How it works
View cameras let you tilt or swing the lens (and film) independently. Done right, this lets the plane of sharp focus tilt away from being parallel to the film, so a flat surface running away from you (a road, a tabletop) can be sharp from front to back even at a wide aperture. The geometry rule that governs this is called the Scheimpflug rule.
The Scheimpflug rule
If you imagine the planes of the film, the lens, and the subject extended out as flat sheets, those three planes all meet along a single line whenever the picture is in focus front to back. Tilting the lens changes the angle of that line and lets you put your plane of focus where you want it.
Tilt angle
How many degrees you tilt the lens (or back). A small tilt of two or three degrees is enough for a typical landscape; a steeper tilt is needed for closer or steeper subjects.
Hinge distance
The distance from the lens to the line where the plane of focus pivots. The modal calculates this from your tilt angle and focal length so you know exactly where the plane of sharp focus crosses the ground.
Depth of field becomes a wedge
On a tilted lens, the depth of field is no longer a flat slab. It is a wedge that is shallow near the camera and gets wider as it goes away. The modal shows the near and far edges of that wedge for your aperture.
When to use a swing instead
Swing is the same idea as tilt but rotated to the horizontal axis. Use swing for receding side walls, fences, or any subject that runs away to the left or right rather than into the distance.