# Calibration sphere & light

The AR 51 calibration sphere is an illuminated ball used to calibrate the cameras' positions across the capture volume — this page covers its size, light output, and where to source it.

## Calibration Sphere

The calibration sphere is an illuminated ball, **30–40 cm in diameter** — for example, [this 40 cm garden-light ball](https://www.amazon.de/-/en/Trango-Garden-Diameter-Outdoor-Lighting/dp/B00J1OL9IS). For larger capture areas, use a bigger sphere.

## Light Bulb

The sphere should emit **a strong, white light** — at least 1800 lumens (for example, a [100 W-equivalent daylight LED](https://www.amazon.com/Listed-6-Pack-100-Replacement-Daylight/dp/B0C9TYD7Y4)).