How to Determine a Diamond’s Optics Even If You’re New

When in-depth research was first performed at leading gemological labs (AGS/GIA) to study and predict light performance based on proportions, the results were revolutionary. It was found that diamonds which possess a certain range of cut proportions tend to exhibit better optical performance. On the contrary, diamonds which didn’t fall within that range (e.g. excessive table size) tend to suffer reductions in brilliance and scintillation. 

And within this range of proportions, the common consensus among the labs is that there isn’t a fix set of “magic numbers” which can create an appealing diamond. Instead, there are many sets of proportions that can yield similar results in a diamond’s optics.

If you think about it, it makes sense. This is because light performance is based on a complex relationship between factors like table/depth percentages and pavilion/crown angles.

Diamond Selector Simulation

depth and table simulator for diamond optics

Besides GIA’s Facetware software, this online visual tool can give you a quick estimate of how proportions can impact optical properties. By sliding the counters to change the depth and table sizes, you can get a rough idea of the diamond’s predicted brilliance.

The Layman’s Method to Determining a Diamond’s Optical Performance

If you hold a poll with jewelry professionals and ask them what they think the most important factor of the 4Cs is, a good majority of them will tell you that it is the diamond’s cut. Yet ironically, most jewelers or salespeople have no basic understanding of what really constitutes to an ideal cut.

In fact, I’ve seen the following scenarios replayed time and time again when I visit jewelry stores. I have had countless experiences with salespeople who are just reading off the sales presentation charts with no clue to what they really represent. Worse still, there are some who simply show you the cut grade from a grading report and make a sweeping statement that all GIA triple excellent cut diamonds are the same. Well, the truth is, they aren’t.

There is an important question that 99% of the jewelers fail to address – how do you differentiate between diamonds which are all graded with the same cut rating? If you have a comparison of 3 GIA triple excellent diamonds, which should you pick for the best light performance?

For most consumers who do not have sufficient experience in viewing diamonds, it can be extremely difficult to tell the differences. However, with the use of tools like the ASET and Idealscope, you can now see and make decisions based on tangible data.

How Do Diamond Evaluation Tools like ASET and Ideal Scope Function?

idealscope with 10X magnification

The ideal scope was first developed in the ’70s by a Japanese gentleman call Mr Okuda based on the principle of using reflectors. In its most basic form, the Idealscope is made of a red-reflecting material placed between a magnifying lens (typically 10X) and the diamond to be evaluated. Mr Okuda’s work was later built upon and evolved into the current model you see to the left.

As you can probably tell, the idealscope is a simple handheld tool (measuring about 5cm in height) used to reveal areas of a diamond that reflect light or leak light. It can also be used in analyzing the optical symmetry of the diamond. For example, in a hearts and arrows diamond, the arrows patterning can be checked for consistency and precision.

consistent arrows patterning of a well cut diamond

Here’s an example of an ideally cut Hearts and Arrows diamond under the Idealscope.

An Introduction to ASET for Optics Evaluation

portable ags aset scope

The ASET (Angular Spectrum Evaluation Tool) is a similar little device developed by the American Gem Society for light performance analysis. At a first glance, you might think the ASET scope looks somewhat identical to the idealscope and resembles a children’s toy.

However, the information provided by the ASET is more detailed due to the use of 3 color bands. And if you didn’t know yet, the ASET image is also used for providing graphical cut information in AGS’s platinum light reports.

The great thing about both these tools is that they can be used to assess both mounted and loose diamonds in a matter of minutes (for best results, a uniform light source and a loose diamond will be preferred).

Also, with the ASET and idealscope, you can capture images for analysis by attaching the scopes to the lens of a camera. Once that is done, you will be able to inspect the images easily on a large screen and do further analysis.

So, Why Don’t Local Stores Offer These Tools for Consumers?

While these are the tools which can help consumers evaluate a diamond, they aren’t available in most jewelry stores. The underlying reasons are simple. As I mentioned earlier, most jewelers have no clue on cut evaluation and are ignorant of the existence of such scopes. More importantly, the majority of diamonds in the market aren’t well cut and it would only hurt the stores to let you view their diamonds critically.

If you intend to shop in a brick and mortar store, I recommend purchasing your own scopes and learning how to use them. Each of these scopes cost about $50 before shipping. Compared to the cost of a diamond ring, this is only a small price to pay for the benefits it offers. Also, you don’t need a set of these 2 scopes. By itself, the ASET scope is more than sufficient for diamond selection purposes.

Here’s the good news. You don’t necessarily need to own or learn to use both of these tools if you don’t want to. Reputable online vendors like Whiteflash or Brian Gavin have professional set ups for capturing these data and offer these services for free.

If you are considering online shopping, I recommend working with these vendors as they have a proven track record of providing great support and high quality diamonds.

On the next page, I’m going to show you how to use these 2 scopes in different scenarios. You will also learn how to interpret the ASET/Idealscope images and use this knowledge to your advantage.

Next Page >>

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  1. Scott-
    November 8, 2014 at 4:29 am

    hi paul,

    where can I buy an ASET and idealscope?

  2. Paul Gian-
    November 8, 2014 at 7:31 am

    You can get it at several places depending on where you live.

    For US/Canada, you can check out this link:
    For Asia, Australia, you can check out this link:

  3. Kpgm-
    April 18, 2015 at 7:33 pm

    I purchased the $180 kit with expert idealscope and aset. The scopes are cheap plastic and are both made in china. They are utter crap in terms of build quality and I was extremely disappointed.

    Garry Holloway is making a KILLING on these.

    That being said, I viewed 40-50 XXX diamonds before settling on the one for my fiance, and 35+ had excellent idealscope and aset images.

    It gave me confidence in the one I chose, but I don’t know if it was exactly necessary.

  4. Paul Gian-
    April 24, 2015 at 5:07 am

    Admittedly, the scopes are very pricey. However, you didn’t have to buy them if you don’t want to. As I mentioned in my article, you can choose to work only with vendors who can provide you with these images for their listings.

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