Direct light is light that reaches the viewer from 45° to 75° above the girdle plane. Our light map shows it in red.
In more detail
This is the bright light from above, outside the zone of the viewer's head. A well-cut round in diamond returns most of its face-up area as direct light.
How we measure it
The simulator's light map classes each face-up ray by the elevation its light came from. Rays from 45° to 75° count as direct.
Related terms
- Light Return: Light Return sorts each point of a face-up stone by the direction its light came from. Its four classes, direct, indirect, contrast and leakage, together cover the whole face-up stone.
- Light map: A light map is a face-up picture of a cut stone, colored by the direction each point's light came from. Red is direct light, green is indirect light, blue is contrast, and a dark color is leakage.
- Indirect light (Light Return): Indirect light is light that reaches the viewer from below 45° above the girdle plane. Our light map shows it in green.
- Contrast (Light Return): Contrast is the part of a face-up stone whose light comes from 75° or higher above the girdle plane. This zone lies within 15° of the line of sight, where the viewer's head is.
- Leakage: Leakage is light that enters a stone and leaves where the viewer cannot see it, mostly through the pavilion. Lower leakage is better.