Which method is primarily used for ensuring focus on specific moving subjects?

The method primarily used for ensuring focus on specific moving subjects is rack focus. Rack focus involves changing the focus of the lens during a shot to shift the viewer's attention from one subject to another, particularly when these subjects are at different distances from the camera. This technique allows cinematographers to create a dynamic storytelling effect, emphasizing the subject that is currently in focus while subtly guiding the audience's eye.

In contrast, deep depth of field keeps a larger portion of the scene in focus, which may not be ideal for isolating or highlighting a particular moving subject. Macro focus is designed for capturing extreme close-ups of small objects and is not typically applied to moving subjects. Camera panning involves moving the camera horizontally or vertically to follow a subject; while it captures motion, it does not specifically manage focus on different elements within the frame. Thus, rack focus is distinctly suited for directing viewer attention to moving subjects through intentional changes in focus.