The overall score is one figure out of 100 that combines our light-performance scores for one cut in one gemstone. The Cut Performance Wheel calls it Global.
In more detail
It compares cuts within one gemstone only; never compare scores across stones. The weights are fixed settings of our method, not measured constants. The T73 round brilliant in diamond scores 89.8.
How we measure it
Overall = 0.34 B + 0.20 F + 0.16 T + 0.10 S + 0.10 Y + 0.10 (100 − leakage). Here B is brilliance, F fire, T tilt, S scintillation and Y symmetry. The census stores the figure unrounded. The Cut Performance Index shows one decimal, and cut pages show whole numbers.
Related terms
- Cut Performance Index: The Cut Performance Index is Digital Gemology's open table of light-performance scores for the cuts we sell, in seven gemstones. It gives each cut brilliance, fire, scintillation, tilt, symmetry, spread, shape-norm, leakage and an overall score.
- 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.
- Fire: Fire is the flashes of spectral color that a cut stone sends out. In our census, fire is the share of returned light whose colors leave more than 0.6° apart.
- Tilt (light performance): Tilt is how much of its face-up brilliance a cut keeps when the stone tilts. Our tilt score compares brilliance at a 20° tilt with brilliance face-up, capped at 100.
- Leakage: Leakage is light that enters a stone and leaves where the viewer cannot see it, mostly through the pavilion. Lower leakage is better.
- 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.