A light table is a translucent diffusing surface, typically white acrylic or opal glass, lit uniformly from below by daylight-balanced fluorescent or LED tubes at approximately 5500 to 6500 Kelvin. In the gem trade it serves as the standard sorting surface for loose parcels, particularly diamonds and small coloured stones, where uniform back-lighting reveals colour, clarity, and proportion irregularities that ordinary overhead light obscures.

Use in the trade

Diamond sorters at cutting centres in Surat, Antwerp, and Ramat Gan grade parcels almost exclusively over light tables, using paper folding boards in white or light grey to compare colour against masters. The diffuse, shadowless illumination eliminates point-source reflections that mask body colour. Coloured-stone dealers use light tables to identify windows, extinction zones, and silk in sapphires, and to sort melee parcels by tone and saturation.

For photography the light table doubles as a back-light source, producing the bright, shadow-free white field characteristic of trade catalogue images. Calibrated colour temperature is essential: the GIA grading laboratory specifies 5500 to 6500 K for diamond colour grading, and most professional sorting tables target this range.

Distinguishing from related tools

A light table is not a lightbox. The lightbox encloses the gem in a chamber for controlled photography, while the light table is an open work surface. It is also distinct from the gemmologist's daylight lamp, which provides overhead rather than transmitted light. Most modern bench setups combine both for thorough examination.