ASET - Table Reflection

In the center of a face-up ASET (Angular Spectrum Evaluation Tool) image of a round diamond is a small area around the culet that represents a reflection of the light entering the table.

In the color coded ASET scope sometimes this area appears red, sometimes green, and sometimes a combination of red and green. So which is better, or does it matter?

The first thing to keep in mind is that BOTH red and green represent light return. The second thing, related specifically to the table reflection, is that the color is a function of the pavilion main angles. Table size and crown angles do not affect it at all.

The ASET is a tool designed to reveal more information about the nature of light return than reflectors like the Ideal Scope. In the ASET hemisphere, the demarcation line between red and green zones is set at 45 degrees. Light entering the diamond above 45º is colored red by the device, below 45º is colored green.

It is the pavilion angle that determines which of those colors you will see in the table reflection in the center of the ASET in face-up view. At pavilion angles right about 40.76º the reflection draws light from the point where red meets green. So pavilion angles of 40.75º will be drawing light from less than 45º and thus be colored green. Pavilion angles of 40.77º will be drawing light from just over 45 degrees and be painted red. Both 40.7º and 40.8º are well within the ‘sweet spot’ of AGS 0 parameters. And there is potentially less than 1/100 of a degree of difference that will toggle this area from red to green.

The graphic below illustrates how the pavilion angle on either side of the toggle point determines the color of the ASET table reflection of a round ideal diamond.

A combination of red and green is indicative that some of the pavilion main facets are slightly below 40.76º and some slightly higher. (The pavilion angle reported on the certificate is the average of the eight pavilion mains). These variations among individual angles can be seen graphically by another great AGS tool called the VPA (Visual Proportion Analyzer).

All other things being equal, from a light performance perspective there is no observable difference between diamonds with different color table reflection in ASET. Super ideal diamonds can display either color, or a combination.

It is interesting to see for yourself this relationship. When you browse A CUT ABOVE® ASET images and see one that is primarily red, you will notice the pavilion angle is *generally 40.7 or more. Primarily green *generally 40.7 or less.

Our guidelines for A CUT ABOVE® prescribe a pavilion angle range of between 40.6-40.9, which is the sweet spot subset of AGS parameters. Thus, you will see many examples of both red and green table reflections as well as combinations represented in our super ideal brand.

If AGS had chosen 40 degrees as the demarcation between red and green, all of our A CUT ABOVE® diamonds would have red centers. But it would not change the diamonds or their phenomenal light performance!