ASET Ray Tracing

ASET stands for the Angular Spectrum Evaluation Tool, developed by the American Gem Society under U.S. Patent No. 7,336,347. It works on a single, elegant premise: our world is lit from above. Light arrives at a diamond from every direction, but not all directions are equal — bright overhead light is more valuable than dim, low-angle light, and the observer’s own head blocks part of the scene entirely.

ASET maps the directions from which light returns to your eye and color-codes them by the angle they came from. The result is a visual record of how a specific diamond actually handles light — not how it should perform on paper, but how it performs in fact.

These angular ranges are not informal usage. They are stated verbatim in Brian Gavin’s U.S. Patent No. 10,405,618, which defines the green hemisphere as low-angle indirect light up to 45°, the red hemisphere as the brightest light from 45 to 75°, and the blue hemisphere as the 75-to-90° zone of observer obstruction — with leakage reading as black, or white under backlighting.

An ideal ASET image — what AGS grades as a “0” for light performance — shows a balanced distribution of red, green, and blue with no significant leakage. The pattern is predominantly red (orange), with controlled green, strategically placed blue creating a clean contrast structure, and no black.

Balance is the entire point. A diamond that maximizes red at the expense of contrast is not the goal; neither is one chasing one metric while sacrificing another. The brightest, most beautiful diamonds are the ones where every zone is held in correct proportion — which is precisely what Optical Balance describes.

An earlier tool, the Ideal-Scope, helped educate a generation of diamond buyers and earned its place in the trade. But ASET superseded it, and for a clear reason.

The Ideal-Scope uses three categories: red for all light return, regardless of its quality; black for obstructed light; and white for leakage. It tells you how much light comes back. What it cannot tell you is whether that light is high-quality direct light or weaker reflected light — everything that returns is the same shade of red.

ASET takes that single red zone and splits it in two: red for intense direct light, green for indirect light. In other words, ASET reveals light quality, not merely quantity. That distinction is why we moved on. We no longer use the Ideal-Scope; ASET is the superior tool.

A round brilliant and a princess cut will never produce the same ASET image, and they are not meant to. A princess naturally shows more green than a round — that is inherent to its geometry, not a flaw. Reading an ASET correctly means knowing the standard for the shape in front of you.

This is why fancy shapes cannot be judged against a round’s template. The skill lies in understanding what an exceptional emerald, cushion, oval, or princess should show — and recognizing when a stone meets that standard rather than mistaking a shape’s natural signature for a deficiency.

No single instrument tells the whole story. Our verification rests on three tools that must all agree:

When all three converge, you have Optical Balance — not a marketing phrase, but a measurable, verifiable standard. It was using AGS ray-tracing software that the late Peter Yantzer, former head of the AGS Laboratories and architect of its Performance-Based Cut Grading System, measured the Brian Gavin Signature cushion at 95% light return and called it the brightest cushion he had ever seen.

This is not theory. Two of Brian Gavin’s United States patents are built directly on the ASET light-performance science described above, and a third carries the same precision into a fancy shape.