Light performance is one of the most remarkable qualities of diamonds, though it is not an attribute that many average diamond shoppers usually look for. Consumers are often more worried about a diamond’s Four Cs - carat weight, cut, color, and clarity. However, it is paramount to investigate the light-handling abilities of a diamond before investing in it. This is gauged through an intricate process that involves specialized gemological equipment.
While all the Four Cs typically impact the light-handling properties of a diamond, it is the cut of the stone that plays the most role. Therefore, while shopping for the ideal diamond, do not simply choose a cut from an aesthetic point of view; instead, establish how it impacts the light performance of the stone because this is the only way to be certain that the diamond sparkles as it ideally should. To fully comprehend how a diamond handles light, it is important to understand the two relevant concepts behind the calculation of the same: Ideal-scope and HCA.
What’s the Ideal-Scope?
Notwithstanding that this concept was popularized by Garry Holloway, the idea, however, was birthed by a Japanese scientist known as Okuda. In the 1970s, Okuda developed various ways of studying the light performance of diamonds by the use of colored reflectors in magnified scopes. The method was later popularized when Garry Holloway came up with the Ideal-scope.
The Ideal-scope is a simple magnifying tube built with red reflectors. It is designed to create a structured light environment; the very environment that is used to determine how a diamond handles light.
To examine the light performance of a diamond, the latter is placed on the Ideal-scope with its girdle aligned with the bottom of the tube. As light enters the crown from above, it is reflected to the observer’s eyes as red. The red light greatly pertains to the diamond’s scintillation. The light that escapes or leaks through the pavilion of the diamond appears white, while the light emanating from the highest angle seems black - the latter being the light that is blocked by the observer’s head.
The developer of the ideal-scope, Garry Holloway FGAA, DipDT, JAA Appraiser, is a renowned geologist turned jeweler. Mr. Holloway founded the Melbourne Precious Metals, presently known as Holloway Diamonds. The Diamond Technology graduate from the Gemological Association of Australia continues to lecture on one of his specialties - the Science of Light™ & Diamond Cut.
Before the ideal-scope was designed, Professor Okuda’s concept had already led to the development of another cutting-edge technology: The Fire Scope™. It was a limited distribution desktop device, and the Ideal-scope tube is its small, portable variant.
Besides gauging a diamond’s light-handling properties, the Ideal-scope may also be used in the grading of optical symmetry. Through the tube, a professional observer can predict the amount of fire and scintillation a diamond has. The information obtained is not only useful for diamond buyers who are keen on investing in an optically symmetrical stone, but it is also resourceful for diamond polishers who can then adjust the disproportional facets and ensure that the stone achieves its ideal optical symmetry.
One of the best things about the ideal-scope is that it can be used with a diamond of any shape, clarity, or color.
How to Interpret the Ideal-scope Images
As is clear from the images above, the ideal-scope can be used to analyze more than just the light performance of a diamond. It can be taken to in order to determine the optical symmetry as well as the proportions of the stone.
Moreover, the black areas represent the light that is returned at high angles. As has already been pointed out, these areas appear dark because the observer’s head blocks the light coming into the tube.
The red areas represent the brightest light that returns to the observer’s eyes while the pink ones represent less intense light.
Areas that appear white or grayish represent the light that is not returned to the observer’s eyes. Instead, the light leaks through the pavilion of the diamond.
Optically symmetrical diamonds are marked by an abundance of red light, with a minimum of white or grey. Such diamonds also sport a pattern of symmetrical black arrows that radiate from their centers.
If a diamond is average cut, it will appear more pinkish in the Ideal-scope, while also having areas of white and gray leakage.
Light leakage, considered a sign of disproportionate facets, is more pronounced in poorly-cut diamonds that also feature chaotic patterns.
Now, the appearance of dark hues through the ideal-scope may come across as counter-intuitive. However, the dark color generally creates a pleasant contrast, adding to the overall brilliance of the stone. Contrary to what many diamond shoppers may believe, white color in ideal-scope imaging is not a plus for a diamond. Leakage indicates that certain facets of the diamond are not proportionally-cushioned, thereby significantly affecting the stone’s light-handling properties.
In terms of proportions, optically symmetrical diamonds feature sharp patterns of arrows that run through the crown. The pattern becomes more chaotic, with a decline in optical symmetry.
The Holloway Cut Adviser (HCA) is an intuitive tool used to analyze the cut of round diamonds. After analyzing the diamonds, the HCA tool renders a score that the user can then interpret to estimate the cut quality of the stone. The main idea behind the development of the HCA was to help consumers determine the fire, brilliance, and scintillation of round diamonds. Hence, unlike the ideal-scope tube, the HCA tool is used almost exclusively for round cut stones.
The HCA is also another popular concept by Garry Holloway who developed the tool in 2001 to help diamond shoppers eliminate as many differentiators as possible in their bid to hunker down on their ideal gems.
For the HCA tool to accurately analyze a diamond, it investigates five parameters of the stone - the Depth %, Crown angle or %, Table %, Culet %, and the Pavilion angle or %. The tool analyzes these values independently in a score of between 0 and 10, following which process it establishes how the values influence the overall cut quality of the round diamond.
Diamonds with a score of 0 or thereabout are considered to be the best cut quality. However, it is almost impossible to come by a diamond with a score of 0; for this would mean that the stone has no performance limitations - a feat impossible to achieve considering that the five major parameters used are always conflicting. This explains why most consumers often look for a score between 1 and 2, in which range diamonds are often classified as Fiery Ideal Cut (FIC), Tolkowsky Ideal Cut (TIC), or Brilliant Ideal Cut (BIC).
According to Mr. Holloway, the HCA should not be used primarily as a diamond selection tool. Instead, the tool should help shoppers to eliminate poor-performing stones. He encourages opting for a score below 2, as that eliminates over 95% of all the world’s diamonds. But if the budget cannot allow it, settle for what is affordable as long as it is closest to 2 on the HCA score.
Holloway further remarks that going for a diamond with a score above 5 on the HCA tool is a false economy. It is so because while the stone may come cheap, its poor cut implies that the diamond’s light performance is way below average. Therefore, chances are that one may end up spending more in having the diamond polished further to achieve an ideal brilliance.
The HCA tool does not only analyze the cut quality of round diamonds depending on the five stated parameters, but it also presents individual scores for the diamond’s Fire, Scintillation, Brilliance, and Spread. Each of these variables is graded in a score chart that includes Poor, Fair, Good, Very Good, and Excellent.
However, issues have always been raised about the HCA’s competency in analyzing these finer aspects of a diamond. For instance, it is unclear how the tool arrives at a diamond’s scintillation without considering factors such as the optical symmetry and the lower girdle facet length.
Another serious concern is the fact that the tool presents its analysis based on basic 2-dimensional data points. The concept appears to disregard the fact that a diamond’s light performance results from how the entire stone’s facets handle light in 3 dimensions. Also, the HCA tool does not account for the facet precision of a diamond. Besides, it rounds up the input measurements for crown and pavilion facets, thus opening up rooms for wide variances in the output scores.
Lastly, the HCA tool does not consider a detailed synthesis of the diamond’s model, but only focuses on the outline of the stone.
Should You Trust Ideal-scope and HCA?
Generally, the Ideal-scope is more reliable than the HCA tool; the fundamental difference between the two being their accuracy. Though each tool examines specific aspects of a diamond, the goal, however, is to establish the diamond’s overall brilliance and scintillation, primarily using the cut.
The Ideal-scope is more accurate, with minimal error margins. It errs when interpreting the imaging results, meaning that they are more due to human oversight.
The most significant drawback of the HCA is the fact that it presents its analysis based on limited parameters. Most of those analyses are arrived at depending on the outline of the diamond, as opposed to its model.
Therefore, a diamond that scores poorly in an ideal-scope or the HCA tool does not necessarily imply that the stone is of a poor cut. At the end of the day, it all comes down to one’s tastes and preferences.
Some consumers view Ideal-scope and that HCA data as more theoretical than practical, further arguing that for a diamond to appear eye-clean is the real deal.
Both the HCA and the ideal-scope are cutting-edge tools that were designed to assist consumers in shopping for diamonds of superior cut. While these tools are still instrumental, they have since been rendered less useful by recent cut grade systems developed by reputable gemological labs: examples of such labs include the American Gem Society and the Gemological Institute of America. It is acceptable to demand an Ideal-scope image and HCA analysis reports when shopping for a diamond, but if the diamond is graded by any professional gemological lab and there is a certificate to show for it, nothing else should be concerning.