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.
In more detail
A stone on a hand is seldom seen exactly face-up. A cut that holds its light when tipped looks steadier. The cap at 100 stops a dim cut from scoring well only because it has little light to lose. The T73 round brilliant in diamond scores 92.
How we measure it
The census runs again with the stone tilted 20°, with 2,200 rays. T = min(100, 100 × B(20°) ÷ B(0°)). The Brightness & Tilt Analysis gives a fuller picture: its figures at 13 tilts from −30° to 30°.
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.
- 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.
- Brightness & Tilt Analysis: The Brightness & Tilt Analysis is a free Digital Gemology tool. It measures how much dome light a cut returns face-up, and how this changes with tilt.
- 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.
- Head shadow: The head shadow is the part of the overhead light that the viewer's own head blocks. In our tools, it is a cone around the line of sight in which no light counts.