When a certain object or subject remains in a shot after a direct cut, whether in the same shape or different one, in the same part of the shot or in another, we get the illusion of a jump. We call it a phi effect. We know four forms of the phi effect.
It arises when an object or subject in adjoining shots is found in different parts of the picture composition (horizontally, vertically or diagonally).
Phi moving closer and moving away
We also call it a phi jump down the optical axis of the lens. The object or subject is filmed in the same parts of the shot surface but with different framing heights.
Objects or subjects are framed in different parts of the picture, with similar or identical framing heights. A phi hit is the basis for editing dialogue scenes, shot with complementary angles of filming (see “Axis of action”).
It arises when different objects or subjects are framed in the same part of the picture.
It arises when the same object or subject is shot in adjoining shots but in a way, that its spacial direction changes within the same shot.
A combination of the listed effects is also possible.