Rack Focus
A focus change that moves the sharp plane from one subject to another within a single continuous shot.
What it is
A rack focus shifts the plane of sharpness from a foreground subject to a background one, or the reverse, while the camera stays still. The focus ring is turned during the take, so the viewer's attention is pulled from one object to the next. Because the change happens inside one shot, it links two things in the frame without a cut.
When to use it
A director uses it to reveal a character who was blurred in the background, or to show that a nearby object matters to someone further away. It suits moments where the story needs the viewer to notice a detail and then the person who reacts to it. Tension often comes from the slow transfer of focus, since the viewer waits for the new subject to resolve.
How to prompt it
Name both subjects and their order: the sharp foreground object first, then the person who becomes sharp. Say that focus shifts or pulls from one to the other, and specify a locked-off camera, since rack focus is not a dolly or pan. Describe which plane starts soft, such as the person being soft and out of focus, so the model knows where the change begins.