How to film for clean video analysis

Good analysis starts before you open TrackStat — it starts with the footage. A few minutes spent on your camera setup saves you far more time later, and makes the spatiotemporal metrics far more reliable. Here’s the setup we recommend.

Get the frame rate right

The single most important setting is frame rate. To resolve contact and flight times accurately you want a high, constant frame rate:

• 120fps is the practical minimum for sprint work.
• 240fps is better, and most modern phones can do it in slow-motion mode.
• A GoPro is excellent here because it records at a genuinely constant frame rate, which keeps your timing measurements honest.

Avoid “auto” modes that quietly drop the frame rate in low light — that’s the most common cause of noisy data.

Watch out for variable frame rate

Phones don’t always record at the speed they advertise. Set an iPhone to 240fps and it will quietly drop to a slower rate as soon as the light gets low — and other apps running in the background can pull the rate down too. The catch is that the file still gets labelled 240fps, even though the camera is no longer capturing 240 genuinely different frames every second. This is called a variable frame rate, and it’s the silent killer of clean timing data.

You can spot it by scrubbing through the footage one frame at a time: the picture stays exactly the same for two or three frames, then jumps. Those repeated frames aren’t real moments in time — the camera simply duplicated the last one to fill the gap. When TrackStat measures contact and flight times across a stretch of duplicated frames, the numbers come out wrong, because the clock says time has passed but the picture says nothing moved.

A few things keep the rate constant and honest:

• Use a GoPro or action camera where you can — they lock to a genuinely constant frame rate rather than easing off when conditions get harder.
• Close background apps before you film, so the camera has the phone’s full attention.
• Give it plenty of light (see below) — this is the single biggest reason a phone holds its high frame rate instead of dropping it.

Position the camera

Place the camera side-on to the runner, perpendicular to the direction of travel, far enough back that you capture two to three full steps in frame. Keep it level and on a tripod — handheld panning introduces motion blur and makes step detection harder.

1. Set up back from the lane based on your camera — around 5 m for a GoPro (its wide lens lets it sit closer), or around 8 m for a phone in landscape.
2. Frame the zone you care about (e.g. the 30–40m mark for max-velocity work).
3. Lock focus and exposure before the rep.

Light it well

You don’t need studio lighting, but you do need enough light. Higher frame rates need more light to avoid dark, blurry frames. Film with the sun behind the camera where you can, and avoid filming directly into glare.

Quick checklist

• 120fps or 240fps, constant
• Side-on, tripod, level
• Two to three steps in frame
• Locked focus and exposure
• Plenty of light, no glare

Nail these and marking up each step in TrackStat becomes quick and consistent — which is exactly what you want when you’re comparing an athlete across a season.