An LED ring light is an annular array of LEDs mounted around the objective lens of a stereomicroscope, providing diffuse, even, top-down illumination of the work directly beneath the lens. In the gemmology and jewellery bench context it is used as a complement to dark-field and fibre-optic illumination, particularly for surface examination, photographic documentation, and any task that benefits from shadow-free overhead light.

Compared with a single overhead lamp or with halogen ring lights of older generation, the LED ring offers several practical advantages. It is cool-running, so it can be left on continuously without thermal effect on heat-sensitive stones. It is bright enough at low power to support photography through the microscope without separate flash. Many modern units offer segmented control (separate sectors of the ring can be switched independently to produce directional shadow effects on demand), variable intensity, and adjustable colour temperature. The latter matters for accurate documentation, where a known colour temperature allows white-balance correction in subsequent photography.

For colour-stone work the ring light is generally used to support, rather than replace, dark-field and fibre-optic illumination. Inclusion examination still relies on the optical contrast that dark-field provides, and treatment witnesses such as the lead-glass blue flash require oblique fibre-optic illumination. The ring light is most useful for surface examination (polish quality, tool marks, hallmark detail), for diamond examination (proportions, symmetry, surface finish), and for documentation photography where flat, even light is required.