Polished spheres (plastic or glass, varying finish) — reveal light direction and reflection on set. Essential for color reference and gaffer analysis.
They stand around on every professional set like little oracles — polished spheres made of plastic or glass that show you in seconds what the light is really doing. Reference spheres are your most important tool when it comes to consistent lighting and later for color calibration. They work on a simple principle: a sphere reflects all light from all directions equally. This means you immediately see which light sources are falling where, where shadows are forming, and how the color temperature is distributed.
In practice, you need at least two different surfaces — one highly polished (smooth sphere with strong reflections) and one matted (diffuse surface with softer reflection). The smooth one shows you the direct light sources and their intensity; the matted one reveals the fill lights and ambient light. During setup, place the spheres directly next to your subject at eye level. If you photograph them with the same camera and lens as the actual shot later, you have an exact reference for color grading — especially important when shooting with multiple cameras or on different shooting days.
In editing and grading, the reference sphere serves as an anchor. You compare the shot with your reference photograph: Are the skin tones consistent? Has the direction of light shifted between takes? A standard Gray Ball (18% gray according to Kodak) is your basic tool; some sets also use ColorChecker Balls with multiple color fields. The decisive advantage: a sphere doesn't lie. It shows you the geometric reality of light — not your personal perception, which is distorted by adaptation and context.
Professionals always keep one or two reference spheres in their equipment bag. They weigh almost nothing, are robust, and save you hours of grading time in post-production. They are indispensable, especially in locations with mixed lighting or on long shooting days where the sun's position changes. Photograph the sphere at least at the beginning and end of each setup — that small extra shot will pay off.