Calibration target: per take. Use the printable 10×7 ChArUco board (9×6 inner corners, 25mm squares, 18mm markers). Minimum quality: , per camera.

The board must be visible in both cameras at the same time, but it does not need to be in the same zone in both views. Zone overlays turn green after analysis. If preview looks mirrored on your device, continue anyway; calibration uses board geometry, not image orientation.

1. Keep both cameras fixed and angled toward the same play area (roughly 20-45 degrees apart).
2. Hold the board so both cameras see all corners in each sampled moment.
3. For each camera, cover all four zones over time (zones can differ between cameras per moment).
4. Tilt/rotate slightly (about 15-30 degrees), and vary distance (near and far).
5. Use a rigid board backing (cardboard/foam core). Curled paper reduces calibration quality.
6. Avoid motion blur; pause briefly (0.5-1s) in each zone.

The timer is guidance only. You can record longer than target and add multiple takes; results are aggregated.

Sweep the calibration board through each highlighted zone and pause briefly when stable. Recommended minimum: . No auto-stop.