Performance · Chapter 14
ASET, Ideal-Scope, and light-performance imaging
What reflector colors can show, what they cannot, and how to read images without turning them into scores.
Diagnostic images make a diamond’s directional light behavior visible under a controlled setup. They are maps of one viewing geometry—not photographs of how the stone will look in every room.
Reflector images encode direction
ASET and Ideal-Scope place a colored environment around a diamond so returned light is coded by its source direction. The resulting pattern can reveal distribution, symmetry, obstruction, and areas where the setup’s light does not return to the camera.
Read ASET colors within the system
In common ASET implementations, red represents light from higher angles, green from lower angles, blue represents obstruction or contrast, and white or black—depending on background—indicates leakage. The balance expected varies by shape and by the device or rendering convention.
Ideal-Scope simplifies the map
Ideal-Scope imagery generally uses red or pink for returned light, black for obstruction, and pale or white areas for leakage. It is especially useful for comparing similarly captured round brilliants, but image exposure, alignment, stone tilt, and background can exaggerate or conceal differences.
Blue and darkness are not defects by default
A controlled amount of obstruction produces contrast, which allows reflections to switch visibly in motion. Interpreting every blue or black area as lost brightness removes the very structure that supports scintillation. Look for balanced distribution rather than one color occupying the maximum area.
Fancy shapes require shape-specific reading
An ASET pattern that is desirable in a round brilliant is not a universal template for an oval, cushion, step cut, or antique style. Facet architecture changes the expected pattern, and a single face-up image may miss behavior visible only through tilt.
Standardize before comparing
Compare images made with the same device, alignment, exposure, and background, and confirm they belong to the exact stone. Then return to neutral video and live observation for fire, transparency, movement, and preference—qualities a static reflector image cannot settle.
Worth remembering: Use diagnostic images to ask better questions, not to replace the diamond with a diagram.
Essential language
- ASET
- Angular Spectrum Evaluation Tool, a reflector system that maps returned light by source angle.
- Ideal-Scope
- A reflector viewer that highlights returned light, obstruction, and leakage with a simplified color scheme.
- Leakage
- Directions where light passes through the pavilion rather than returning toward the viewing position.
- Alignment
- The centering and orientation of the stone relative to the camera and reflector.
- Ray tracing
- Computer modeling of light paths through a measured three-dimensional diamond.
Questions to take with you
- Which reflector system and color convention produced this image?
- Was the stone centered, level, and photographed with consistent exposure?
- Is the contrast distributed, or concentrated in a persistent dark zone?
- Am I applying round-brilliant expectations to a different facet architecture?
- Does ordinary video confirm the pattern suggested by the diagnostic image?