GEMEX Light Performance Report

[ospray]

In your opinion, is the GEMEX Light Performance Report a reliable standard of quality?

It rates each diamond from "Low" to "Very High" on White Light, Color Light, and Scintillation. Obviously, Very High is better than Low...but is this just a subjective standard?

And the 5 light views LOOK cool, but are they meaningful?

I guess I WANT this report to be a good indicator of performance, but I am wondering how skeptical I should be. I want to hear your opinions!

 

[Paul-Antwerp]

Simple answer: NO.

More in detail: do not trust the line-bars. Some people with a lot of experience claim that they can deduct certain aspects of the stone from studying the various light-views. They might be able to, they may not.

Live long,

 

[Rhino]

Date: 12/7/2008 11:43:39 AM
Author:ospray
In your opinion, is the GEMEX Light Performance Report a reliable standard of quality?

The GemEx BrillianceScope is a digital optical examination that that accurately reflects diamond light performance in spot lighting conditions. Ie. If a diamond scores great results via the GemEx Light Performance Report it is a good, unbiased confirmation that the diamond will have great fire and sparkle (not necessarily brightness and contrast as there are different optical exams to test for those optical characteristics) and is why I personally employ the technology in helping to communicate light performance quality in certain shapes we feature.

At the same time it is important not to allow yourself to get caught up in "analysis paralysis". For example a diamond that scores "high", "very high" "high" on the BrillianceScope can be just as fiery and have as much sparkle scintillation as one that scores 3 "very highs". It''s results (as it is with any technology reporting light performance) must be tempered with wisdom and an awareness of that technologies limitations as well as its strengths.

It rates each diamond from ''Low'' to ''Very High'' on White Light, Color Light, and Scintillation. Obviously, Very High is better than Low...but is this just a subjective standard?

Subjectivity is removed because a BrillianceScope can not reason. It''s is hard cold report showing the results of reflecting spot lighting into a diamond over 5 main portions of the crown which are then digitally examined and computated via its results. Subjectivity enters the equation perhaps when interpreting those results. In the 8 years I''ve been using it and studying various proportion sets and minor facet constructions with it I can tell you from experience that good results via the BrillianceScope = a diamond with great visual performance in spot lighting.

In short if a manufacturer is marketing a diamond with top fire/sparkle and the GemEx Report results in the low/medium range with nothing "very high" that is a pretty solid indicator to further investigate the claims so see what is causing the lower results. Based on my studies of it''s results along with studying light leakage in reflector based technologies show that low GemEx Results are caused generally caused from excess leakage. In fact we''ve ran across bogusly taken IS images that showed strong light return via IS imagery but when put in the GemEx showed poor/mediocre results. When examined through our reflectors we saw exactly why too.

And the 5 light views LOOK cool, but are they meaningful?

Yes and no.

Yes in the sense that those images do show real/actual facets that light up in a practical examination of diamond in spot lighting. Ie. In those images you see pavilion mains lighting up with strong fire and it is a fact that the pavilion mains of Hearts & Arrows rounds throw off strong fire in a practical observation. Same with intense reflections coming off the stars and other facets too.

No in the sense that the examination is done in a controlled lit environment. One in which you will never see in a practicall exam. In the GemEx exam light is being evenly distributed over the portions of the crown it is reflecting the light into. In real world observation we do not enjoy such structured lighting and in the case of the GemEx you''d have to walk around with an intense spot light attached to your nose to always see that view.

We live in an assymetrical world with lighting that is constantly changing.

I guess I WANT this report to be a good indicator of performance, but I am wondering how skeptical I should be. I want to hear your opinions!

If I''ve said it once I''ve said it a million times. A technology is only as good as it correllates with human observation. As a hybrid bricks and mortar store/internet seller of diamonds I am a strong and staunch advocate of technologies that communicate diamond quality, appearance and performance and the more information, in my professional opinion, the better informed your decision and purchase will be. At the same time I stress to those consulting any technology that they be aware of their limitations as well as their strengths. I make every attempt to approach each of them with a healthy degree of skepticism.

Best regards,

 

[WinkHPD]

I will disagree with my friend Jon.

This tool was looked at by both GIA and AGS with the idea of using it in their diamond cut studies.

Both laboratories found it lacking in reliability and consistency of grading. (Don''t like this grade, run it again.)

It is also possible to cut a diamond to perform high on the machine and it tends to reward diamonds with longer lower girdle facets.

There are MUCH better tools out there for you to use, such as the ASET.

Wink

 

[Rhino]

Date: 12/7/2008 6:27:21 PM
Author: Wink
I will disagree with my friend Jon.

This tool was looked at by both GIA and AGS with the idea of using it in their diamond cut studies.

Both laboratories found it lacking in reliability and consistency of grading. (Don''t like this grade, run it again.)

Without written statements by them I wouldn''t jump to conclusions but perhaps they were looking for a machine that gave them a metric for overall optics or perhaps one that better communicated the more common view ... brightness with patterned scintillation. One GIA gemologist whom I know actually showed me a diamond he considered a good example that demonstrated what they considered to be a major flaw with the Bscope and it happened to be a diamond that scored great on the Bscope yet had poor brightness and contrast. I told him I was fully aware of this and I do have it published as one of the limitations of the technology. While that diamond did have mediocre brightness/contrast it did in fact have excellent fire and sparkle and the BrillianceScope accurately communicated that. As I mentioned in my post above it accurately reflects diamond appearance in spot lighting, not diffuse/suffuse. Also as mentioned above if one is going to consult its results understand the limitations as well as its strengths.

With regard to its consistency ... I had the opportunity to run the same diamond 2 years later. The results were the same. If results change the changes are what would be neglible. Not drastic by any means.

It is also possible to cut a diamond to perform high on the machine and it tends to reward diamonds with longer lower girdle facets.

No disrespect but this isn''t fully accurate Wink. Back in the day when upper half facets and painting/digging were not measureable (at least by our lab) I had made this statement when the most I could measure on diamonds and could note were lower girdle facet lengths. Of super ideal cut diamonds that were being cut that I had access to the only measureable difference I could note that could be measured at that time back then were differences in lower girdle facet lengths (and at that time it was 75% lower halves as compared to about 78-79% lower halves). Now with Helium we see that it wasn''t lower halves so much so than it was the fact that the stones with the shorter lower girdles were severely painted. It is a fact however that if you lengthen lower halves you alter the sparkle pattern of a diamond and most observers would agree that the longer you lengthen them, the more pin fire is added.

In fairness though there are many diamonds we test with shorter lower girdles (in the 74-76% zone) that do in fact score triple very highs on the technology.

And don''t get me wrong ... I like ASET too but neither technology is an end all be all solution. I view each one as an aid to helping the buyer make a more educated decision, when in fact they are educated as to what the technology is showing and also what it isn''t.

Hope you are having a great weekend.

Peace,

 

[strmrdr]

From watching the results over the years the B-scope is interesting for rounds, near useless for anything else and counter productive for step cuts.

The biggest variable in the results is the c/p angle combination it prefers a certain return pattern.
By looking at the ETAS/DETAS in diamcalc 3 you can easily spot the ones it prefers.
LGF% has little effect in some c/p combos and a much greater effect in others on the results.
Painting has a very large effect and the angles and lgf% have to be perfectly balanced in a way the B-scope prefers to overcome it.

Is it useful, well my opinion is somewhere between its great and its useless.
Carefully applied it can be used to select similar performing diamonds in direct light.
Is that a good thing? Well yes if you like that personality in your diamonds.

 

[Rhino]

Date: 12/7/2008 9:47:14 PM
Author: strmrdr
From watching the results over the years the B-scope is interesting for rounds, near useless for anything else and counter productive for step cuts.

The biggest variable in the results is the c/p angle combination it prefers a certain return pattern.
By looking at the ETAS/DETAS in diamcalc 3 you can easily spot the ones it prefers.
LGF% has little effect in some c/p combos and a much greater effect in others on the results.
Painting has a very large effect and the angles and lgf% have to be perfectly balanced in a way the B-scope prefers to overcome it.

Is it useful, well my opinion is somewhere between its great and its useless.
Carefully applied it can be used to select similar performing diamonds in direct light.
Is that a good thing? Well yes if you like that personality in your diamonds.

Totally hear ya on the fancies. Interesting observation with the fancies though that differs from rounds ... Great results still = great fire/sparkle but there are fancies however, as you note Asscher''s and I would add certain Cushions that can have seemingly mediocre Bscope results that show excellent fire too. It''s one reason why we don''t feature those results on certain fancies. I''d say the same however about reflector images with fancies too. There happens to be pretty strong correllation with our DiamXray results and Bscope that I''ve noted. I say withdraw what useful info you can from it and spit out the bones.

All the best,

 

[strmrdr]

The one on the left would for the same overall light return would have a b-scope score lower than the one on the right due to lgf% only. (73% vs 80% lgf%)
On the one to the right the dots are more concentrated towards the center and middle where they are more spread out on the left.
This shift is even more so for other combinations of c/p angles.

 

[strmrdr]

In this combo 4 degrees painting has little effect on the middle area and they would score the same on the b-scope for any given brightness.
The difference are outside of the primary zone for the B-scope to measure the return.

 

[ospray]

Wow, thanks for all the feedback and intelligent discussion. I feel smarter listening to you people.

 

[oldminer]

The answers you have received are just about the perfect balance of how much to trust "scores", "numbers" and "measures". You definitely can "trust" them, but only to varying extents depending on the shape and the exacting circumstances of the diamond and with you, as a consumer.

Using these several tools, not just Gemex, will go a long way to scrteening out the poorer choices and making the viable choices more clear to you. This is all good news for consumers.

The deal is not so good or as safe when you are forced to depend on selected information a seller chooses to provide on a diamond which you can''t be sure of until you see it in person. Certain tools are better predictors on round diamonds than on other shapes. Certain lightin scenarios apply to grading devices yet diamonds are worn in many differing light environments in the course of a day. There is a lot of complexity, but we are getting consumers to a safe destination in many of these cases.