A slow zoom is a gradual, deliberate change in focal length over a sustained period, creating a barely perceptible magnification or reduction of the subject that builds tension, intimacy, or unease without the obvious intrusion of a fast zoom cut. Unlike a snap zoom or crash zoom that announces itself immediately, a slow zoom works almost subliminally, the frame tightening or loosening over many seconds in a way that the audience feels emotionally before they consciously register the camera movement.

The slow zoom in has a long history as a technique for building psychological intensity. Gradually tightening on a face over the course of a scene creates a growing sense of pressure, scrutiny, or revelation. The audience becomes increasingly focused on the subject as peripheral elements are squeezed out of frame, creating an involuntary narrowing of attention that mirrors or amplifies the emotional state the scene is building toward. Slow zooms out perform the inverse function: gradually revealing more context, introducing a sense of withdrawal, or creating the feeling of distance growing between the viewer and the subject. The technique is associated with 1970s cinematography and certain directors known for their use of the long lens as an emotional tool, and it has experienced revivals in contemporary prestige drama and horror filmmaking as a tool that communicates character psychology through subtle visual means. The distinction between a very slow dolly and a slow zoom is perceptible to trained eyes in the compression of the background that a zoom produces, but to most audiences the emotional effect is the primary experience.

In AI video generation, "slow zoom in" or "slow zoom out" with a specified duration and intensity, such as "gradual slow zoom into the face over ten seconds," guides the model toward producing the sustained optical movement that characterizes this technique.