Shape-norm compares a cut's brilliance with a ceiling for its shape family. It shows how close a cut comes to what cuts of its family reach, rather than to a round.
In more detail
The ceilings are 93 for round brilliants, 86 for fancy brilliants, 76 for step cuts and 64 for other cuts. The score is capped at 125, so it can go above 100.
How we measure it
Shape-norm = min(125, 100 × B ÷ C). B is census brilliance, and C is the ceiling of the cut's family. For your own file, the Wheel sorts the stone into a round brilliant, a step cut or a fancy brilliant.
Related terms
- Brilliance: Brilliance is the white light that a cut stone returns to the viewer. In our census, it is the share of entering light that leaves through the crown toward the viewer.
- Cut Performance Wheel: The Cut Performance Wheel is a free Digital Gemology tool. It draws eight light-performance scores of one cut, in one gemstone, on a wheel.
- Fixed settings: Fixed settings are the constants of our scoring method that we chose rather than measured. They are the same for every cut, so the scores can rank cuts within one gemstone.
- Light census: The light census is our ray tracer behind the Cut Performance Wheel, the cut-page scores and the Cut Performance Index. It drops a fixed set of rays on a stone from above and counts where each one leaves.