Rack Focus
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A rack focus moves the sharp plane from one subject or distance to another during a continuous shot, while the composition stays largely the same. Attention changes because the helical turns, not because the camera cuts or dollies.
Narrative function
A brass key is sharp on a desk. The woman in the doorway is soft.
Over about two seconds the key goes, her face arrives. Nobody moved.
The audience felt a handoff inside one space. Use it to change who owns the shot without cutting: pursuer and pursued, a clue and a face, a listener and the person who just entered.
A slow rack is a sentence. A snap rack is a jab.
It is the wrong tool when both planes must stay sharp (that is deep focus or a split diopter) or when the camera should physically travel. If details morph instead of going in and out of focus, the model invented a dissolve.
How it works
Mark two distances. Rehearse timing with the first AC.
Keep the head still for a clean demonstration, or coordinate the pull with a small move. Wide-open glass makes the rack readable.
Lens breathing may change field of view slightly. Decide if that is wanted.
Prompt: locked camera, named near and far subjects, a two-second pull, shallow depth of field, no zoom.
When to use it
Focus holds on a foreground key, then pulls to the figure in the doorway over about two seconds. Do not rack when the scene needs both faces sharp at once, or when a cut would be cleaner.
Compared with similar shots
Shallow Focus is a static thin plane. A rack is that plane moving.
Split Diopter keeps two distances sharp at once with a seam. Deep Focus keeps a continuous range sharp so no pull is required.
Push In travels the camera. The rack does not change the map, only the focus mark.
In film
Peking Opera Blues shifts focus from the pursued figure to the pursuing policeman inside one composition. The Graduate uses selective focus to organize Benjamin against the people around him.
The Player treats the pull as a long sentence of attention.
Peking Opera Blues 1986Focus shifts from the pursued figure to the pursuing policeman.
The Graduate 1967Selective focus organizes attention between Benjamin and surrounding figures.
Prompt it
Name both planes and the duration. Still: Rack focus between planes around [Subject], a two-second pull from foreground to the figure or the reverse.
Video: Focus racks from a named foreground element onto [Subject] over about two seconds, shallow depth of field, locked camera, no zoom.
What usually goes wrong
Wrong cousin: a cut, a morph, or both planes staying sharp. Tell: no defocus, details melting, or a zoom pretending to be a pull.
Fix: hold framing, send one plane soft while the other comes true, and keep identities stable.
Questions
What is rack focus in film?
A focus pull from one distance plane to another during the shot. The frame stays, attention moves. Also called a focus pull, slow rack, or snap rack.
Rack focus vs shallow focus
Shallow focus is the state of a thin sharp plane. Rack focus is the act of moving that plane from one subject to another.
When should I use rack focus?
When you need a reveal or a handoff of attention without cutting. Do not use it if both planes must remain sharp.
How do I prompt rack focus for AI image or video?
For video, lock the camera, name the near and far subjects, and give a duration (about two seconds). For stills, describe the pull as a pair of planes, one arriving, one leaving.
Melies can generate this Rack Focus
Melies is the AI filmmaking workspace. This Rack Focus opens with the optical prompt loaded, so the effect has a physical cause in the frame.