AGS Advanced ASET Diamond Certificate

An additional ASET light map will now accompany the AGSL reports of all new* round diamonds in the A CUT ABOVE® brand. The new Whiteflash ‘Advanced ASET’ will include two face up ASET maps rendered at 30 and 40 degrees of obscuration providing information on multiple aspects of light performance, and a pavilion view that illustrates the hearts pattern and the optical precision of the cut (also referred to as optical symmetry). The branded AGS A CUT ABOVE® proprietary certificate with Advanced ASET is the most comprehensive diamond document available in the market, and currently the only diamond report containing three separate light maps.
AGS Advanced ASET Certificate

Background on ASET

ASET (Angular Spectrum Evaluation Tool) is the graphical tool at the heart of the American Gem Society Laboratories’ sophisticated light performance cut grading system. ASET light maps provide important information about how a diamond is handling light. The grading system, which involves computerized ray tracing of an accurate 3D scan of the diamond measures brightness, light leakage, contrast and fire.
Contrast, seen in Blue on an ASET light map is a vitally important component of diamond beauty that impacts both brightness and sparkle. In the proper amount and distribution contrast enhances our perception of brilliance. Too much and a diamond can look dark – too little and the diamond may lack sparkle. This crucial aspect of light performance, as you will see, is one in which the observer physically factors in to the equation.
For more information please see our page on ASET.

The Curious Role of the Observer – Diamonds Need Us!

As strange as it sounds, the observer actually plays an important role in the amount of critical structured contrast present in a diamond, and must be factored into the facet design. You might say it’s a concept that is hard to wrap your head around! In fact, as we closely observe a diamond some of the light that would otherwise fall on the crown of the gem is blocked by our heads (represented by the blue zone in ASET). Some facets, particularly the pavilion mains, reflect this head shadow back to our eye creating contrast with the other facets that are illuminated. As we observe the diamond in motion, the contrast that we help to create results in a light/dark or on/off pattern of blinking facets. This dynamic contrast generates scintillation and sparkle.
ASET Hemisphere

Why Both 30° And 40°?

The ASET structured environment features a 30 degree cone of obscuration that is approximately the angular range of the light that is blocked by an observer’s head when viewing a diamond at typical viewing distance of about 10 inches (15° on either side of the line of sight perpendicular to the table of the diamond). If we draw the diamond very close to view it, the range that is obstructed increases to about 40 degrees. A diamond must be able to acquire ample light from outside this range or it will have diminished brightness. The two face up maps of 30° and 40° will show the amount of obscuration at close and very close viewing distances.

The light performance grading algorithm includes measuring contrast at 40 degrees to ensure that a diamond does not have too much contrast at very close viewing, or when an observer has big hair or is wearing a hat. The algorithm measures contrast by a formula of 2 parts 30° and 1 part 40°.  Deficits in contrast will result in a penalty in grading. A grade of AGS Ideal is not possible unless contrast is within very strict limits, including what happens at 40.

Standard ASET Light Map at 33.5°

The ASET light map on standard AGS Platinum reports is printed at a cone of obscuration of 33.5 degrees. This corresponds to the average of the 30° and 40° computations referenced above. The new Advanced ASET consists of both the 30° and 40° light maps, as opposed to the single 33.5. In addition to the advantage of providing a look at how the diamond will behave at 40°, the 30° light map on the cert will more closely correspond to actual ASET photos which are taken in a standardized environment with a cone closely approximating 30 degrees.
Below are samples of actual photos taken by the Whiteflash Team compared to the computer generated light maps on the AGS reports. The first set compares our actual photo to the standard light map on a Platinum report. The second set compares our actual photo to the light maps on the new Advanced ASET report. Note the differences in the first set deriving from the 3.5° difference - there is a bit more blue contrast.  In the second set , you can see how close our actual 30 is to the Light Map 30 on the Advanced ASET certificate.
Actual ASET Photo vs Computer Generated ASET
Actual ASET Photo vs Computer Generated ASET

Dynamic Contrast

At the boundaries of structured contrast lies the fascinating and all-important domain of dynamic contrast. These are the pinpoint areas that turn from dark to light, from ‘on to off”. As that happens we experience the ‘life’ in the stone. In addition to being fundamental to scintillation, the dynamic contrast areas also promote fire. Because our ability to experience fire, or colored sparkles, depends so heavily on the light source (see our full article on diamond fire), it is interesting to note that head shadow is also clipping the light source and making it more likely that we will see a colored sparkle. Those boundary areas of dynamic contrast contribute to that magical effect. The ASET 40 shows dynamic contrast in a darker shade of blue.
Tolkowsky 30 and 30.5 and 40 degree ASET
ASET Maps of a Tolkowsky Ideal at all three cones of obscuration. Contrast is seen in blue.
The ASET 40 shows dynamic contrast in a darker shade of blue.

Computer Generated Light Maps and ASET Photos

The ASET maps on AGS reports are computer generated from an accurate 3D model of the diamond as captured by one of the highly accurate non-contact measuring devices in wide use in the diamond industry today. AGSL light performance grading is a mathematical system based upon the physics of light. Brightness, contrast, leakage and fire can all be precisely computed and rendered in ASET maps of various kinds. This is a repeatable and reliable method of scientific cut grading. There are instrumentation variations, but the measuring devices today have extremely small margins of error. This makes a computer generated ASET light map very accurate.
Actual ASET photos, such as those taken on all Whiteflash diamonds, also have some variables. Despite using equipment and a process that is very consistent and accurate, very small deviations in orientation of the diamond to the camera lens can result in very small variations. Ideally you will have both a computer generated map AND a photo. This will provide confirmation with each image validating the other.
Please note that in actual ASET photos some of the contrast may appear black rather than blue. This is the reflection of the camera lens that is peeking through in the very middle of the blue zone.

Symmetry and Precision Revealed by ASET

ASET Light Maps also provide valuable information about faceting precision. The patterns and symmetry of the colors are a good indication of the level of craftsmanship. 3D symmetry, also known as optical precision, does not happen by chance. It is the result of a philosophy of cutting for maximum beauty, and having the equipment, skill and time to execute that goal.
The pavilion view ASET is intended specifically for this purpose. Since a diamond is not viewed from the bottom, light performance from this perspective is not relevant. But a pattern of uniform hearts can only be achieved if the diamond has been cut with flawless precision in three dimensions.
This level of precision also impacts light performance. The tiny system of mirrors that is a diamond can only operate efficiently and accurately if all facets are aligned properly in three dimensional space. When aligned with precision, the optical potential of the cut design is maximized.
On the AGS website the importance of optical symmetry is expressed quite evocatively: “If Light Performance is a rock star, then Optical Symmetry is a maestro. Just as a maestro would be focused on the execution and precision of a performance, so is Optical Symmetry.”

The Value of Advanced ASET for the Consumer

The mission of the American Gem Society is to provide the market with the highest levels of consumer education and consumer protection. As members of the AGS, Whiteflash shares these goals. The Advanced ASET with the addition of the 40 degree light map gives the consumer assurance that the diamond performs well, even at closer than normal viewing distances. The pavilion view ASET demonstrates the level of facet precision and craftsmanship. These maps are particularly valuable when comparing other diamonds, apples to apples, from vendors who also provide comprehensive information about the light performance of the diamonds they offer.
Old ASET AGS Certificate
AGS Certificate with a Standard Dual Light Map (click to enlarge)
New Advanced ASET AGS Certificate
AGS Certificate with a Advanced ASET Light Map (click to enlarge)
* Diamonds with certificates dated before the published date of this article may not have the Advanced ASET light map.

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