Skip to content

What makes a good video

The analysis has to find a 12 cm ball moving at 25 metres per second, and work out where your feet, hips and shoulders are, from a single camera. What you film decides what it can do. Nothing later in the process recovers footage that never showed the throw clearly.

The short version

  • One camera, side on, at about chest height.
  • Landscape, never portrait.
  • Whole throw in frame — from the first wind to well after release.
  • Steady. Prop the phone up or use a tripod. Handheld works, but steadier is better.
  • 1080p, 30 or 60 frames per second. Not 4K, not slow motion.
  • Good light, and a background the ball stands out against.

Where to stand

Set the camera to the side of the circle, roughly level with the thrower's chest, far enough back that the thrower and the hammer stay inside the frame for the entire throw — including the winds, when the ball swings widest, and the follow-through after release. A throw that leaves the frame partway through can still be analysed, but every frame the ball is outside the picture is a frame that has to be estimated instead of measured.

Side-on matters. From directly in front or behind, the turns compress into each other and the depth of the orbit is guesswork.

Phone settings that matter

  • 1080p at 30 fps is the target. 60 fps is fine and slightly better.
  • Landscape. Rotate the phone.
  • Lock the camera down. Set the phone against a bag, a fence, anything solid. A tripod is better. If the camera drifts during the throw, the reconstruction has to work out how much of the movement was you and how much was the camera.
  • Slow motion. Phone slow-motion modes rewrite the timing information in the file, and the timing is what speed is calculated from.
  • 4K. Bigger is not better here; it is slower and buys nothing.
  • Anything under about 20 frames per second. Below that the ball moves too far between frames to be tracked reliably.
  • Portrait video. You lose the width you need at exactly the moment the hammer is furthest out.

If you are filming with the ThrowSage phone app

The app exists to take the settings above off your hands. When you record inside it:

  • Format is chosen for you. It picks the best the phone offers in this order — 1080p at 60 fps, then 1080p at 30, then 720p — and shows the choice in the corner (for example 1080p • 60fps). It never records 4K and never slow motion.
  • It tells you to turn the phone. Hold it upright and a banner asks you to rotate to landscape before you start.
  • Tripod or handheld is detected. For about two seconds after the screen opens it reads the phone's gyroscope. Held still, it reports Auto — Tripod: stabilization is switched off (it would fight a still camera) and focus is locked the moment you press record. Moving, it reports Auto — Handheld and leaves stabilization on. Tap the label to override, or choose Tripod, far to zoom in 4× when the phone has to sit well back from the circle.
  • A shaky handheld clip can be steadied afterwards. Each recording has a Stabilize action; use it before syncing if the camera moved.
  • Sync replaces the upload step. Recordings stay on the phone until you tag the athlete and press Sync on that throw — nothing goes anywhere on its own, so ten takes can become two analyses.

What the app cannot do is stand in the right place, keep the whole throw in frame, or light the ball. Those stay with you; the rest of this page still applies.

Light and background

The ball is small, dark, and moving fast enough to blur. It needs to be distinguishable from whatever is behind it.

  • Film with the light behind the camera, not behind the thrower.
  • Avoid a background full of other round dark objects — heads in a crowd, other implements on the ground, equipment bags.
  • Dusk, heavy shade and indoor cages are the hardest conditions. They work, but expect to spend more time correcting the tracking afterwards.

A quick self-check before you upload

Play the video back and ask:

  • Can you see the ball in every frame? If you cannot, the software will not either.
  • Is the whole throw there — winds, turns, release, follow-through?
  • Did the camera stay still?
  • Is it landscape, and does it look like normal-speed footage?

Four yeses means upload it. A no is worth a re-film.

Next: Uploading a video