Chapter 2 - Diamond Education Made Easy (Part 5 - Evaluating Light Performance Using Idealscope/ASET Images)
In this previous part of the Diamond Education Made Easy, I'd discussed about the significance of Hearts and Arrows on the optical symmetry of the diamond. If you'd missed it, you could check the links down below:
Chapter 2: Diamond Education Made Easy (Part 2 - Diamond Grading System)
Chapter 2: Diamond Education Made Easy (Part 3 - Diamond Structure and HCA Score Calculator)
Chapter 2: Diamond Education Made Easy (Part 4 - The Significance of Hearts & Arrows)
Chapter 2: Diamond Education Made Easy (Part 3 - Diamond Structure and HCA Score Calculator)
Chapter 2: Diamond Education Made Easy (Part 4 - The Significance of Hearts & Arrows)
Typically, a good H&A diamond with a great HCA score means that you've selected one of the top 1% of diamonds in the entire world! And usually these diamonds would give you a good visual impact, and enough to please the woman of your dreams. But do we settle for good, or are we going for the best of the best? After all, we don't do normal here, do we.
Since we're going for the creme of the crop and so that we don't get conned by shop keepers, you may want to know how to qualitatively evaluate the light performance of the diamond, whether are we getting the best of what we'd paid for.
And how do we evaluate the light performance of the diamond?
Idealscope or ASET Images
Idealscope images is a scope that is able to let you evaluate how much light is leaking out from the diamond. Because as I'd mentioned, if too much light leaks out at the side, you're going to end up with a relatively dull diamond.
This is an Ideal scope
ASET, also known as Angular Spectrum Evaluation Tool works similarly with the Idealscope, in the sense that they also evaluate how much light is leaking out from the diamond. However, it also shows us additional information such as the visual proportion of light return across the diamond. This is represented by the various colours in the picture.
This is an ASET scope
Let's have a look at the difference between the ASET and Idealscope images below for the same diamond. So how do we evaluate it to observe the light leakage?
Image obtained from YourDiamondTeacher
It's very simple really. The redder it is, the better. And this rule applies to both Idealscope and ASET images.
Idealscope Images
In an Idealscope image, there are only four colours that you'll need to pay attention to: Red, Black, Light Red and White/clear colour.
Image obtained from Pricescope
Red (Highly desirable): The red colour represents the areas of light reflection. So the more red parts there is in the image, the better it is.
Black (Highly desirable): The black/dark colour represents the contrast in the diamond. A significant contrast leads to a better scintillation, and makes your diamond appear brighter.
Light red (Undesirable): While it is still red, the lighter red represents that that particular area is reflecting back less light.
White/clear (Stay away at all cost): If you see an Idealscope image with plenty of white, reject the diamond immediately. The white colour represents areas of significant light leakage. Choose a diamond with minimal light leakage.
Therefore as you can see, the light performance highly depends on the cut of the diamond. In the market, there are many diamonds which are touted to have the best 4Cs, but what are the use of those if they do not perform the way as we want them to? I'd attached a sample of the IdealScope reference chart as below, as a comparison of various cuts with the light performance of the diamond.
So to summarize the Idealscope image analysis, the redder the image is, the more light it is reflected into your eyes, the better the diamond is in terms of light performance.
ASET Images
In ASET images instead, the colour contour represents the angle of light that is entering the diamond. This differs from the Idealscope image as the Idealscope image analyzes the light performance without regards to the light entering angle.
Image obtained from YourDiamondTeacher
The blue colour represents the light that enters in from 75 - 90 degree angle. Typically, the light path through this angle would be obstructed, due to surroundings (i.e. your head that is viewing the diamond. Haha.). That being said, it is still desirable to have some blue areas in the ASET image, as these areas would provide the contrast to make your diamond appear brighter.
Red: 45 - 75 degrees
Between all the angles as mentioned above, the light that enters into the diamond between 45 - 75 degrees angle would reflect the brightest. Highly desirable to see lots of red.
The light that enters between 0 to 45 degrees would be represented as a green spot on the ASET image. These areas are reflecting lesser light, and is therefore considered less bright compared to the areas in red.
Image obtained from YourDiamondTeacher
Similarly to the Idealscope images, the white/clear colour shown on the ASET image are highly undesirable, as these represent the light leakages from the diamond.
Image from YourDiamondTeacher
An excellent diamond with a fantastic light performance will demonstrate a ASET image that is fully red and blue, with minimal green and white. From the diagram as above, you can clearly see that for the Average and Above Average diamond, there are many green and white/clear areas that signifies less light return, with significant light leakages as well.
Idealscope versus ASET Images. Which is the better tool?
Now that is a fantastic question. Both tools have many similarities, as both are meant to evaluate the light performance of the diamond. Analysis wise is similar as well, as the redder it is, the better the diamond is expected to perform.
The only difference is that the Idealscope treats all light entering in as the same, which means that it does not take into account the angle of the light entering. When this happens, you'll not be able to tell whether the entering light is within the optimum region (45 - 75 degree) for best light return. The ASET image, on the other hand would be able to differentiate the degree of light entering and how it returns to our eyes. Lets take an example of a G VVS2 diamond from Pricescope:
The two pictures above are from the exact same diamond. According to what we understand from the Idealscope image, this diamond is said to have a great light performance, as the image has abundance of bright red colour, with minimal white and light red.
However when we compare it with the ASET image, we're in for a major surprise. There are alot of green and white areas in the image, which means that there are less light return, with light leakages from the diamond. This suggests that the light that is reflected back into our eyes are from the 0-45 degree region which is less desirable in terms of brightness.
So when the Idealscope analyzes the diamond, it assumes that all the light entering are from the same plane. Therefore, the diamond indeed does a good job in reflecting light from all planes and angles. yet if we're looking at the 'desirable' light return at the optimum angle, this diamond is unfortunately not doing it's job.
Summary
So the above is the gist about what I do understand about Idealscope and ASET image. If you're still very confused on how to analyze, it's ok. There's only one major summary after this long article.
WHEN IN DOUBT, GO RED
I doubt you'll go wrong with choosing an Idealscope/ASET image that is full with red colour. Haha.
As for which tool is better, I'll say ASET gives you more information. But for a round diamond, Idealscope should be good enough. Why do I say so? The difference between a diamond with a good ASET image and a 'not-so-good' ASET image, assuming that the 4Cs and Idealscope are very similar is very minute, and could not be easily appreciated with the eyes.
So unless you're such a perfectionist or a gem collector, and are very nit picky with all this small details, you do not have to discard a diamond with a less than ideal ASET image. In the finale of this series (Hallelujah!), I'll be presenting a 5-step easy guide on how to choose a diamond that best fits your requirement, and to discuss my diamond hunting experience in mainstream jewelry stores in Malaysia.
Extra reading material:
4. What is the Difference Between ASET And Ideal Scope Images?5. Ideal Scope Vs ASET Scope Diamond Images
6. What ASET reveals that Ideal-scope does not
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