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.
In more detail
The census settings are a 6.9° light cone, a 64° viewing limit, a 0.6° fire threshold and a 20° tilt. The scoring settings are the overall weights, the scintillation constant 45 and the symmetry factor 6. They also include the 61.5% reference depth and the shape-family ceilings 93, 86, 76 and 64. Because of them, the scores rank cuts against each other; they are not physical constants.
How we measure it
The Cut Performance Index lists the fixed settings with the formulas that use them. The overall weights are 0.34, 0.20, 0.16, 0.10, 0.10 and 0.10.
Related terms
- 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.
- Overall score: 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.
- 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.
- Shape-norm: 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.
- Spread (light performance): Spread is an estimate of a cut's face-up size for its weight, compared with a stone 61.5% deep. Above 100 means the cut faces up larger for its weight than that reference.