Split Diopter

A method that cuts a close-up lens (a diopter) in half and puts only that half in front of the camera lens. The side with the close-up lens focuses on a near subject, and the side without it focuses on a far one, giving the frame two planes of focus. Both subjects are sharp at once, but the distance in between is blurred, and a seam appears between the two areas. That is why the seam is often hidden along a line already in the frame, like a door frame or the edge of a table. It was popular from the 1970s to the 1990s and is rare today.

Camera position seen at an angle from above. One bunny stands front left, and another stands about 3 m behind on the right.

Camera view. The left half focuses on the front bunny and the right half on the back bunny, so both are sharp, with a softly blurred seam running down the middle.

How it feels

Tension
Contrast
Standoff
Unnatural
70s cinema

When to use it

Fitting a close-up of a face in front and something happening far behind into one shot
Setting a near person and a far person against each other with equal weight
Front-to-back distances too large even for deep focus
Giving the feel of a 1970s-1990s film

In the movies

The Untouchables (1987) · Source: Movieclips (YouTube) · Original video

Jaws (1975) · Source: Movieclips (YouTube) · Original video

Jaws 1975
Cinematographer Bill Butler. An American Society of Cinematographers (ASC) article gives it as a classic example of split diopter. The specific scene has not been confirmed.
Close Encounters of the Third Kind 1977
Cinematographer Vilmos Zsigmond. An ASC article gives it as a classic example of split diopter. The specific scene has not been confirmed.
Star Trek: The Motion Picture 1979
Cinematographer Richard H. Kline. An ASC article gives it as a classic example of split diopter. The specific scene has not been confirmed.
The Untouchables 1987
Cinematographer Stephen H. Burum. An ASC article gives it as a classic example of split diopter. The specific scene has not been confirmed.
The War of the Roses 1989
Cinematographer Stephen H. Burum. An ASC article gives it as a classic example of split diopter. The specific scene has not been confirmed.

Not to be confused with

Deep Focus: Deep focus is sharp all the way from front to back without a break. A split diopter is sharp only at two planes, near and far, with blur in between.
Rack Focus: A rack focus makes front and back sharp in turn; a split diopter makes them sharp at the same time.
Macro: Putting the same close-up lens over the whole lens instead of half gives macro, filming close things big.

Prompt

Keyword

split diopter shot

Descriptive

Split diopter shot: the rabbit-masked man's face very close on the left is sharp, and the second figure far behind on the right is also sharp, with a soft blurred seam between them.

Try these combinations

Split diopter + 70s thriller: two faces, front and back
Split diopter shot, a man in close-up on the left and a woman far behind on the right, both the near face and the far figure in sharp focus at the same time, 1970s thriller
Low angle + split diopter: a phone and a detective
Low-angle split diopter shot, a telephone on the desk in the foreground and a detective at the door in the background, both in sharp focus at the same time