2026-10-19 · Birdia Blog

How to Analyze Your Own Swing Video

How to Film So the Lines Actually Mean Something

A line drawn over a badly filmed video lies to you. Dr. Young-Hoo Kwon, in his biomechanics research, stresses a basic limitation: a phone video is a 2D projection of a 3D motion. If the camera isn't square to the plane you're trying to measure, the angles get distorted by parallax. That's why:

• Two fixed views: face-on for lateral movement and down-the-line (behind the target line) for the swing plane.
• Tripod, same spot every time: if you move the camera between sessions, you can't compare lines session to session.
• No zoom, no tilted camera: a phone angled just a few degrees changes the apparent club plane.

The Lines a Coach Draws — and What Each One Reveals

1. Plane line (down-the-line view). Ben Hogan, in Five Lessons, describes the plane as a tilted pane of glass running from the ball to the shoulders. In video, the practical version is extending the shaft line at address. If the club sits well above that line on the backswing, the plane is too upright; if it drops below, it's too flat. David Leadbetter, in The Golf Swing, builds his entire diagnosis around plane.

2. Circle on the head (both views). The point isn't that the head has to stay perfectly still — it's checking whether it moves a lot going back or dips down toward the ball.

3. Vertical line on the trail hip (face-on). TPI defines sway as excessive lateral movement of the lower body away from the target on the backswing. If the hip clearly crosses that line, you've got sway.

4. Line at the glutes at address (down-the-line). This is TPI's reference for early extension: if the pelvis moves off that line and drifts toward the ball on the downswing, you're losing spine angle.

5. The frame-count stopwatch. This is the most objective measurement you can make at home. John Novosel, in Tour Tempo, timed pro swings on video and found a 3:1 ratio between backswing and downswing. At 30 frames per second, his benchmark rhythms are 21/7, 24/8, and 27/9 frames (backswing/downswing). Count from the first move of the club to the top of the backswing, then from there to impact.

What AI Automates — and What It Still Can't See

Disclosure: Birdia is our product. What a computer-vision app does well is the repetitive part: detecting the phases and measuring the same references on every swing, without you drawing anything yourself. Birdia, for instance, separates takeaway, backswing, downswing, and finish on-device and calculates your tempo ratio against Novosel's 3:1 on every video.

The limitations are real, and worth being upfront about:

• Clubface at impact doesn't show up reliably at 30-60 fps. According to TrackMan's ball flight laws, starting direction depends mostly on the clubface, and curve on the face-to-path difference. That's measured by a radar, not a phone camera.
• The 2D error persists: if you film at an angle, AI will measure a distorted image with perfect precision.
• A line isn't a diagnosis: the cause of early extension can be technical or physical. If something hurts, see a physical therapist or doctor before forcing new positions.

Sources

• Ben Hogan — Five Lessons: The Modern Fundamentals of Golf.
• David Leadbetter — The Golf Swing.
• John Novosel — Tour Tempo.
• TPI (Titleist Performance Institute) — definiciones de sway y extensión temprana.
• TrackMan — Ball Flight Laws.
• Dr. Young-Hoo Kwon — biomecánica del swing y análisis de vídeo 2D/3D.

Frequently asked questions

What's the best camera angle for analyzing your swing?

Both, because each one shows you something different. Down-the-line reveals plane and early extension; face-on reveals sway, head movement, and weight shift. Film both on a tripod with the camera square to avoid the parallax Kwon warns about.

Can I measure my tempo without any app?

Yes, by counting frames. Film at 30 fps, count the frames of your backswing and the frames of your downswing to impact, then divide. Novosel found a 3:1 ratio in tour pros, with benchmark counts of 21/7, 24/8, or 27/9 frames.

Can a video app tell me why I slice?

Only partly. It can flag associated body patterns, like a plane that's too upright, but according to TrackMan's ball flight laws a slice comes from a clubface open to the path, and face angle at impact isn't reliably measured with a phone camera. For that you need a radar.