A light box, in the gem and jewellery context, is a small enclosed photographic environment with diffused interior illumination, used to photograph gemstones and finished jewellery under consistent and controllable lighting. The box typically has white or grey walls, a translucent diffusion layer between the light sources and the subject, and one or more openings for the camera. Both LED and fluorescent illumination are used, with LED predominating in current practice for its colour-temperature consistency and low heat output.

For the working trade light boxes serve two distinct functions. First, they provide a reproducible photographic setting for inventory imaging and online listings. The diffuse field eliminates harsh specular highlights, permits the gem's internal colour and dispersion to register accurately, and makes setting metals appear neutral rather than gold-cast or blue-cast. Second, light boxes calibrated to a defined colour temperature, typically 5000K to 6500K, support consistent colour grading of coloured stones, and are used by some gem labs and graders as an adjunct to formal grading lamps.

Distinct from a light box is the GIA DiamondDock or comparable diamond grading lamp, which is engineered to a specific spectral output for diamond colour grading. A general-purpose light box should not be substituted for a grading lamp where formal colour grading is being performed.