Part 4: The AGS Performance Cut Grade System
A Common Sense Approach to Assessing Light Performance

Sometimes things can sound initially more complicated than they are in reality.  This is the case with the AGS Performance Cut Grade system. Yes, there are several patented technologies encompassing the system with enough technobabble to satisfy the nerdiest among us, and yes, the fine details of the system are mathematical and technical. However, the IDEAS behind the system are based on good old common sense. If you want to break out your pocket protector and get into the technical details of the AGS Performance Cut Grade system, then by all means, read the peer-reviewed articles, patents, and other publications. But if you’re a big-picture kind of person, you’re at the right place.  

What does a diamond do? What is its nature? What are you seeing when you look at a diamond?  

The answer is beautiful. What you see in a diamond is everything in the panorama surrounding the stone including you! The bright sparkles you see are the lights above your head or the windows beside you, or even the light from your TV. The darker areas in the diamond may be the shirt you are wearing, the bookcase against the wall, or the smile on your face. 

The main point is that the complex pattern of light and dark in the diamond is really a fun house view of the surrounding world. Look closely, and you will notice that the diamond is partitioned into myriad tiny regions, each a virtual window into the surrounding world. As the diamond or the viewer moves, the scenery changes. Bright lights are seen through some of the virtual windows, creating dazzling sparkles as the stone comes alive.

So what makes a diamond appear bright?

There’s a simple (common sense) answer. Diamonds appear bright if the virtual windows are pointing toward the brightest areas of the surrounding world. This idea is the foundation of much of the AGS Performance Cut Grade system and is the essence of the “Light Performance Maps” ( ASET maps) included on the Platinum DQD documents.


Where are the brightest areas of the world? 

Look around, and you will observe that the world is lit from above. Therefore, diamonds with virtual windows pointing toward the higher places will tend to be brighter than those pointing to the lower. This is true, except for one caveat
: If a virtual window is pointing too high, then it is your own face you will likely see and not the brighter world behind it. Interestingly, it is this obscuration effect of your own body and head that can create some of the most striking and visually appealing contrast patterns in a diamond. One such example is the familiar “arrows” pattern in the standard Round Brilliant. Not only can a diamond’s contrast pattern be visually interesting, it also can contribute to the brilliance of the stone by making the adjacent regions in the diamond appear brighter.   
There you have it. While the implementation of the AGS Performance Cut Grade system may be mathematical and technical, the underlying ideas are based on easy-to-understand concepts and straightforward observations. Simply put, diamonds appear bright if they are cut to draw light from the brightest areas of the world. Among other things, this idea implies that the brightest diamonds will exhibit a minimum amount of light leakage and will not draw too much light from high angles where the observer’s head can obscure light sources. While not a complete technical description of the AGS Performance Cut Grade system, these concepts, as well as the others discussed in this section, serve as the big-picture ideas behind much of the AGS Performance Cut Grade system.