What Is an ASET Image & How to Evaluate It? (A Full Guide + FAQ)

We’ve all heard about the 4Cs. So, if we have those then do we really need an ASET image? And what is that anyway?!

Whilst the typical 4Cs diamond quality grading system does a fabulous job of helping us choose a quality diamond, where the cut is concerned we can certainly go one step further.🏃🏻‍♀️

When the cut of a diamond is the main determining factor of its brilliance, fire and scintillation, it surely doesn’t hurt to gather even more information, does it?

This is where the ASET image comes in.

The ASET image provides even more, in-depth information about how your diamond dances and plays with the light—the most important thing to know about a diamond!

So let’s get started and figure out what this ASET image really has to offer and whether we need it when buying our next diamond.

ASET Scope and ASET Image
Image (Right): Whiteflash

What is an ASET Image and what is the framework?

Well, let’s start with the basics, shall we?

ASET stands for Angular Spectrum Evaluation Tool. I know, fancy! This ASET device was created by the AGS (American Gem Society) and is at the very heart of their light performance-based cut grading system.

Whilst we can certainly use the knowledge we already have of diamonds to make an educated decision as to the quality of the stone, the ASET image allows us to take it one step further.

Looking at a diamond, we can use gut instinct alongside diamond quality grading information to think, "AHA! What a stunningly brilliant diamond!" Or perhaps, alternatively, "Hmm… we can do better!" Yet, the ASET image is an extraordinarily simple tool that quickly and effectively provides a heap ton more information about how well a diamond handles light.😎

The brilliance and fire of a diamond are the essences of its incomparable beauty, so understanding the cut quality and light performance of a diamond in greater detail could be key in choosing a truly exquisite diamond.

Released in 2005 by the AGS, this grading system is the most advanced and scientifically vetted cut grading system in the diamond marketplace.

And the ASET image itself is actually very simple…

Red, Blue, Green, Black, or WHITE!
In the most simplistic terms, the ASET image analyzes a diamond that has shown red, blue, and green colors under special lighting sources. The image itself portrays a beautiful pattern that highlights any areas of light leakage and important information about how the diamond handles the light (more on that in a short tick!)

Have you ever looked through a kaleidoscope? The ASET image has a very similar appearance!

What type of color distribution should we expect in an ASET image?

Time to dive a little deeper.

As mentioned, the ASET device is actually surprisingly simple. The image is color-coded using red, blue, green, and black (or white), and by understanding what these colors represent we can begin to understand how effectively a diamond plays and manipulates the light.

So, let’s break it down!

ASET Image: Diamond Light Reflection From Different Angles

RED - The red color within the ASET image represents the brightest light that allows the diamond to shine with extraordinary brilliance! As you can imagine, when we see a lot of red within these images, it’s a GOOD THING!👍🏻 This is the light that strikes the diamond at an angle within the range of 45-75 degrees.

BLUE - The blue areas represent the areas of contrast within the diamond. That being the pattern of light and dark that is aesthetically pleasing to the eye (in a well-cut diamond that is!) These patterns should be symmetrical, balanced, and evenly distributed. The blue color is light typically reflected between a range of 75-90 degrees.

GREEN - The green color shows areas within the diamond that still reflect light (as the red color shows) however, it’s generally less bright than the red areas of light reflection. The green color represents light that is reflected between 0 and 45 degrees. Ideally, we would like to see a lot more red than green within these ASET images. However, it is not uncommon for the table in the center of the stone to reflect red OR green, and sometimes a combination of both.

BLACK (Or WHITE) - Now, areas of black (or white) typically represent the areas of light leakage. Which literally means the areas in the diamond where light is actually lost. As you can imagine, this is the most undesirable color and we want as little of this in the ASET image as possible!

A Whiteflash Diamond and Its ASET Image Provided by the Jeweler
A Whiteflash diamond, and its ASET image provided by the jeweler (AGS-104112218022)

Why was the ASET invented?

Very good question!

After all, we have diamond quality grading systems in place (such as the GIA) why would we need the help of ASET?

Let’s begin answering this question by looking back over the anatomy of the diamond.

Diamond Anatomy

What makes a diamond such a desirable stone is its sheer brilliance, fire and scintillation. The extraordinary light performance allows a well-cut diamond to dance in the light and sparkle like a star in the sky.

And this light performance is mostly attributed to arguably the most important C of the 4Cs grading system—CUT. Yet, when most people think about the cut of a diamond, they naturally think about the SHAPE rather than its cut quality.

But the cut is so much more than the shape of the diamond!

What do we actually mean by diamond CUT?
The cut is actually specific to a diamond’s proportions, symmetry, and polish. We’re talking about the evenness of its patterns and how balanced its angles and edges appear.

All of these proportions must work in harmony with one another and so we do not grade a diamond by considering its individual proportions but instead, we consider how each proportion relates to one another!

As you can see, it’s so much more than just the shape!

Taking the above round brilliant cut diamond above as an example, the GIA clearly shows the various aspects of this diamond that need to be taken into consideration when determining the cut quality of the stone.

Different Proportions of a Diamond (GIA)
Diagram: GIA (Gemological Institute of America)
  • Table Size - An Excellent cut diamond will generally consist of a table size between 52 and 62 percent.
  • Total Depth - This is the diamond’s overall depth, from the very top to the very bottom!
  • Pavilion Depth - The pavilion depth is what you could consider as the bottom half of the diamond. A diamond with a pavilion depth that is too deep or too shallow will often suffer from light leakage (and we don’t want that!)
  • Pavilion Angle - To be considered excellent, the pavilion angle should fall between 40.6 and 41.8 degrees where all other proportions are optimized.
  • Crown Height - This is what you might consider being the top half of the diamond. Again, the crown height can greatly affect a diamond’s ability to reflect and disperse light.
  • Crown Angle - A well-cut diamond should consist of a crown angle that falls between 31.5 and 36.5 degrees.
  • Girdle Thickness - The girdle is the middle portion of the diamond, in between the crown and the pavilion. A girdle thickness that is medium to slightly thick is ideal here—not too thick and not too thin!
  • Lower Girdle/Half Facet Length - This area is what defines the contrast of a round cut brilliant which in turn adds or distracts from the brilliance of a diamond. A well-cut diamond will fall between 65 and 90 percent.
  • Culet - The culet is a small facet at the very bottom of the diamond. To the naked eye, this can be difficult to see but it is there mostly to prevent the point of the diamond from chipping. A very small or small culet on a GIA report is generally considered as one component of an excellent cut.

Mathematical methods vs. ASET analysis

So, as you can see, there are a lot of mathematical parameters to consider when distinguishing the cut quality of a diamond! And whilst these are recognized industry-wide, there’s a very good reason why AGS also conducts performance-based ASET-analysis to evaluate light performance…

⚠️Because even though there might only be a slight difference in two different diamonds specs (in reference to their percentages and angles etc) there could be a HUGE difference in their light performance.

And light performance is what MATTERS, right?

The reason, therefore, that the ASET was invented to greater evaluate the light performance of a diamond and also provide a comprehensive and deeper visual understanding of cut quality for customers.

AGS ASET Images on the Diamond Report (No. 104112218022)
ASET images of a Whiteflash diamond on the AGS report (No.: 104112218022)

This allows us much more information about:

  1. How effectively a diamond is making use of the light available
  2. How evenly light is reflecting throughout the diamond
Prior to ASET
Before the invention of ASET, mathematical ray tracing was used to estimate how well a round brilliant diamond handled light. However, this only took into account 17 of the 58 facets!

  • The table facet
  • 8 crown facets
  • 8 pavilion main facets

Sarin Technology is used to measure all angles, percentages, and proportions of a diamond which is then used to determine the cut grade.

This is still used by the GIA Gem Trade Laboratory to this day.

However the AGS ASET framework measures and evaluates all 58 facets and the stone’s overall light performance, so you can imagine just how much more information this gives us!

Is ASET image evaluation a must for a diamond purchase?

Let’s not mess around, shall we?

Is an ASET image evaluation a must for a diamond purchase…Absolutely not.🙂 There are no rule books here! You can consider these ASET images to be an added bonus. A really incredible and handy bonus!

Whilst AGS has ASET images on their reports, GIA-graded diamonds do not. The GIA focuses on those mathematical parameters mentioned above and clearly reports information in relation to the other Cs—color, clarity, and carat weight.

The important thing to note here is that whilst ASET images would likely be an added cherry on top of a dazzling cake, it is most important that the diamond you intend to purchase is graded by a top-class authority (like GIA) as opposed to a lesser-known laboratory.

This is so we know that the cut grade is absolutely trustworthy and you are certain to be getting what you pay for!

Perhaps the most attractive thing about the ASET image is that it gives customers a more comprehensive and visual understanding of a diamond’s cut quality and light performance. Which can be incredibly helpful during the buying process.

📝Our recommendation? Always review or verify the light performance of the diamond through a high magnification loop or online using a 360-degree video of the actual diamond before making a decision.

And make sure to grab that diamond quality certificate from a reputable lab!

ASET images by AGS vs. ASET images by jewelers
Listen up! It’s important to note that some jewelers have developed their own ASET technology and create their own ASET images for their diamonds.

It’s essential that you are aware that these may not be as accurate as AGS ASET images as they may not have access to such sophisticated and scientifically designed equipment or follow the strict standardized process that AGS adheres to.

There are pros and cons to these in-house technologies but what is worth checking is whether or not it is in fact an AGS ASET so that you have complete transparency.

BONUS: ASET images vs. Idealscope images

The basic principles of the idealscope are much the same as the ASET. In a very similar fashion, it’s a very simple technology that provides us with a visualization of a diamond’s light performance.

ASET Image vs. Idealscope Image (Whiteflash Diamond AGS-104112218022)
ASET image (L) vs. Idealscope Image (R) | Whiteflash AGS-104112218022

The idealscope is a reflector tool (much like the ASET) that was born out of the findings of a Japanese scientist in the 1970’s.

Let’s take a look at the main differences between the ASET and the Idealscope using round brilliant cut diamonds as an example:


  • More advanced technology using blue, green, red, and black colors to show areas of light performance.
  • Can compare the ASET image of your diamond to a reference chart showing a variety of pattern and color combinations that range from average, above average, very good, and excellent.
  • Contains a lot more information!
  • Works well for round brilliant diamonds as well as other fancy shaped diamonds.
  • Requires greater knowledge to interpret.


  • Consists of a more simple black lens and a red reflecting material. Red displays the light return and areas of black indicate contrast with white displaying light leakage.
  • Can look through idealscope and compare to simple reference chart to evaluate symmetry, light performance, and proportions.
  • Contains less information.
  • Does not work well for fancy shaped diamonds.
  • Perfect for a diamond novice looking for a little bit more information.

Other frequently asked questions about ASET images

Time to answer those faqs!

What is an ideal table reflection in an ASET image?

The color code for the table can appear as both red or green. Now, remember, both of these colors represent light return and so it is not so much that one is better than the other, simply that they offer a different kind of light return.

What is important to note here is that the color of the table reflection is actually distinguished as a function of the pavilion’s main angles—not by the table size or crown angles!

In short, there isn’t really an ideal table reflection because as mentioned previously, each element or proportion of the diamond cannot be measured individually. Everything is relevant to one another.

You can have both a green and red reflected table and they can both produce a stunning diamond although they will have slightly different light reflective qualities.

Which jewelers provide ASET images?

Both Brian Gavin and Whiteflash offer ASET imaging with their diamonds. But remember, these ASET images provided by the jewelers might not be as accurate as those ASET images on the AGS diamond reports. Always give priority to the ASG ASET images when making decisions, if the diamonds are graded by AGS.

(💡But also remember, ASET imaging isn’t a MUST in the buying process. Just make sure to have a certified laboratory diamond quality report, such as a GIA diamond quality report)

Everything ASET images and more

There is a lot of information to take away here but don’t let it overwhelm you!

The ASET technology is simplistic, incredibly insightful and a great visualization aid to help you in the buying process. Although it is not imperative, it can certainly provide greater insight and put your mind at ease knowing that you are in fact buying a great quality cut diamond!

Be sure to check with a reputable jeweler if you have any concerns and enjoy the color display of the ASET technology and all of the information it provides!😊

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