What iPhone video can—and cannot—show about swing path.
Two-dimensional phone video can help discuss visible bat and body relationships. It cannot reconstruct a complete three-dimensional bat path from a single ordinary clip.
Choose the view for the path question
A side view can show the bat relative to the body and contact area. A rear or front view may help discuss direction. Each view hides depth.
Keep the bat visible
Use good light, enough distance, and a frame rate appropriate for the motion when available. Motion blur can hide the barrel between frames.
Mark reference areas, not a fake trajectory
Use lines for posture, contact zone, shoulder direction, or another visible reference. Do not draw a smooth path through frames that the camera never captured.
Align the same hitting phase
Compare the bat and body around heel plant, contact, and extension rather than matching clips only by elapsed time.
Separate outcome from the visible movement
Ball flight and contact quality matter, but one result does not fully explain the movement. Keep both pieces of evidence in the session note.
Use specialized tracking for precise bat metrics
Dedicated sensors or multi-camera systems are the appropriate tools when you need calibrated 3D path, attack angle, or bat-speed measurement.