GEMex Shows a Dim Look but High Score

[Octopus_loves_blingbling]

Hi,
I found many diamonds shows a dim look but have high scores on their Gemex images.I have no idea why this happened. Here is a an example comes with two diamonds.
The first one goes with 1.73 carats, D color, astor cut, VS1, Faint Fluorescence. The second one goes with 1.4 carats, E color, astor cut, VVS1, Faint Fluorescence. These two diamonds have almost the same proportion & similar light performance based on the Gemex. However, they show totally different "basic color" in the Gemex images. What I mean about "basic color" is the color shows on the area beside the inner 8 arrows and outer 8 arrows of the diamond. The 1.73 carats diamond shows a dim look on the "basic color" than that of 1.4 carats diamond.

I attached these two diamonds Gemex image, GIA reports, links on bluenile, and a comparison screenshot between these two diamonds' Gemex images (1.4 above 1.73 below).
1.73 Carats https://www.bluenile.com/au/diamond...AMONDS&track=viewDiamondDetails&action=newTab
1.4 Carats https://www.bluenile.com/au/diamond...AMONDS&track=viewDiamondDetails&action=newTab

I am confused by why the 1.73 diamond shows a dim look on its Gemex images and if there is any reason for this phenomenon . And if possible looking for the answer of "is that good or bad to have a dim "basic color" in the Gemex images?"

 

[Octopus_loves_blingbling]

@Rhino please help

 

[YoLaL]

Both diamonds have a very nice proportions and good light performance under the Gemex.Is not a bad thing and not to worry so much on the dimming look and its normal under the Gemex..

 

[Lorelei]

@Rhino please help

Hi Octopus,

Jon should be around presently, I know he used to use Gemex, not sure if he still does but meanwhile, this link should be helpful.

https://www.gemex.com/certification/light-performance-certificate/lightperformancemeasurement.

The lighting you mention is just a feature of the Gemex tool, like some diamonds look dark in some spotlighting, it's a way of evaluating under these lighting conditions if I remember correctly. Both of the diamonds you linked look superb, no concerns there.

 

[John P]

Short answer: The 'dim look' is simply a function of the methodology.

Pros of GemEx: It reliably identifies good performers. And it gives information that can be useful in the hands of those who have professional experience correlating various outputs with actual diamond samples. @Rhino was an early adopter and can comment there.

Cons of GemEx: The results are environment specific, so they're not applicable to every illumination scenario. In fact, we know there are ways to cut diamonds so they max out GemEx scores, but may not be your maximum choice. In live purchasing situations a shopper’s eyes can overrule the sliding scores.

Prior discussion here.
https://www.pricescope.com/community/threads/brilliancescope-revisited.89969/

 

[Octopus_loves_blingbling]

Hi Octopus,

Jon should be around presently, I know he used to use Gemex, not sure if he still does but meanwhile, this link should be helpful.

https://www.gemex.com/certification/light-performance-certificate/lightperformancemeasurement.

The lighting you mention is just a feature of the Gemex tool, like some diamonds look dark in some spotlighting, it's a way of evaluating under these lighting conditions if I remember correctly. Both of the diamonds you linked look superb, no concerns there.

Thank you for your information. Can I safely say that the bright "basic color" is better than the dim "basic color" in Gemex images?

 

[Rhino]

Greetings Octopus,

You wouldn't happen to live in an Octopus' Garden?

Ok... Off the cuff I'm thinking the light vs dark background or body colors could be the result of a few things.

• It could be as simple as a difference in camera settings between the 2 scans.
• It could possibly be due to the presence of graining levels within each gem. The darker one having less of it.
• It could be the possibility of the presence of fluorescence.
• A combo of the two.

Looking at the GIA Reports it appears both have faint fluoro which shouldn't be enough to make that kind of difference so you could rule out the 3rd option which leaves us with 2 possibilities.

The faint with certain levels of graining ... possible.
Camera settings altered between the scans.

It's one of those cases where technology can and never will replace human gemological vetting.

Hope that helps.

Kindest regards,
Rhino

 

[Garry H (Cut Nut)]

Never been a fan, and after seeing cutters work out how to game the GemEx system, I am even less impressed. The red rings indicate the positions in angular orientation for the light ring in GemEx. I have seen engineers pull the devise apart and measure them all.

So make a tiny change in pavilion angle, 40.75 to 40.90 and walla!

 

[YoLaL]

Wow!

Never been a fan, and after seeing cutters work out how to game the GemEx system, I am even less impressed. The red rings indicate the positions in angular orientation for the light ring in GemEx. I have seen engineers pull the devise apart and measure them all.

So make a tiny change in pavilion angle, 40.75 to 40.90 and walla!

 

[Octopus_loves_blingbling]

Greetings Octopus,

You wouldn't happen to live in an Octopus' Garden?

Ok... Off the cuff I'm thinking the light vs dark background or body colors could be the result of a few things.

• It could be as simple as a difference in camera settings between the 2 scans.
• It could possibly be due to the presence of graining levels within each gem. The darker one having less of it.
• It could be the possibility of the presence of fluorescence.
• A combo of the two.

Looking at the GIA Reports it appears both have faint fluoro which shouldn't be enough to make that kind of difference so you could rule out the 3rd option which leaves us with 2 possibilities.

The faint with certain levels of graining ... possible.
Camera settings altered between the scans.

It's one of those cases where technology can and never will replace human gemological vetting.

Hope that helps.

Kindest regards,
Rhino

Thank you so much

 

[Rhino]

Garry's right. Here's the thing revealed from the graphic Garry is showing.

In the GemEx it handsomely rewards diamonds that grab and reflect light from the 75-90 degree angular spectrum. That's 15 degrees from center each way or 30 degrees in total. The GemEx aperature in the dome expands that to 36. You can observe that in the graphics above as it is the "arrows" which are giving off the strongest flashes in the GemEx.

While it is true that observing diamonds in spot lighting will grab and reflect light from those angles and in fact give off strong fire from the arrows (or pavilion mains) it is equally true that when observing the same diamonds they can not be bright in diffuse/office/natural lighting environments. Why? Because the reflections entering the diamond from a 75-90 or in the case of GemEx a 72-90 degree angular spectrum are reflections of head/body shadow.

This is generally not going to be the case in H&A diamonds as you still have plenty of reflections coming to you from the lower halves but I've seen diamonds perform well on GemEx that had too much obstruction yet perform fine on the technology.

You may be a good looking individual but unless you're wearing a mask or jacket with light bulbs on it ... a poor source of illumination.

Bottom line ... regardless of what technology you are consulting in an online purchase I highly recommend vetting by a qualified G-man.

Peace,
Rhino

 

[Garry H (Cut Nut)]

Well said Jon.
A good diamond should look good in almost all lighting.

 

[Octopus_loves_blingbling]

Thank you Rhino. Thank you Garry.

GemEx report somehow showed me a misleading light angle schematic diagram for its 5 measurements. I read Garry's paper issued on GAA Journal and used a protractor to measure these light angles and thought all the last four measurements of GemEx report have angles over 30 degrees. In this case, I might only rely on GemEx to measure the diamond's light performance symmetry.

I am curious how likely a diamond with exact Tolkowsky cut proportion and good light performance symmetry in Gemex would show a bad result in its real ASET. The problem is that the GIA and GemEx are the only two I can get from online purchasing

Thank you again

 

[blueMA]

My personal preference between the two is the 1.73 carats stone.

 

[Octopus_loves_blingbling]

Thank you Rhino. Thank you Garry.

GemEx report somehow showed me a misleading light angle schematic diagram for its 5 measurements. I read Garry's paper issued on GAA Journal and used a protractor to measure these light angles and thought all the last four measurements of GemEx report have angles over 30 degrees. In this case, I might only rely on GemEx to measure the diamond's light performance symmetry.

I am curious how likely a diamond with exact Tolkowsky cut proportion and good light performance symmetry in Gemex would show a bad result in its real ASET. The problem is that the GIA and GemEx are the only two I can get from online purchasing

Thank you again

When I said over "30 degrees" I mean light spectrums come below 60 degrees, which is not true shown by the experts.

I am curious how likely a diamond with exact Tolkowsky (34.5 crown and 40.8 pavilion) cut proportion and good light performance symmetry in Gemex would show a bad result in its real ASET.

Or how likely a diamond with exact Tolkowsky cut proportion and good ASET score would show a bad light performance in real life? Does advanced Sarin Diamond report help in this case? It seems Sarin report provides any measure (e.g. crown angle) with all the 8 directions measurement instead of only one or an average number.

Please help

 

[Karl_K]

Its not open so any information is reverse engineering the devise and or the results.
Frankly there is not enough known as factual information to answer your question.

 

[blueMA]

Anyway, I am curious how likely a diamond with exact Tolkowsky (41.5 crown and 40.8 pavilion) cut proportion and good light performance symmetry in Gemex would show a bad result in its real ASET.

A bit of correction for future readers - The T ideal is 34.5 crown with a 40.75 pavillion.

Or how likely a diamond with exact Tolkowsky cut proportion and good ASET score would show a bad light performance in real life?

Probably unlikely as long as the stone is cut with precision with good optical symmetry. In addition, just because a stone is cut to T ideal doesn't mean it'll be more beautiful or necessarily perform better than other less than super-ideal stones IRL.

 

[Octopus_loves_blingbling]

A bit of correction for future readers - The T ideal is 34.5 crown with a 40.75 pavillion.



Probably unlikely as long as the stone is cut with precision with good optical symmetry. In addition, just because a stone is cut to T ideal doesn't mean it'll be more beautiful or necessarily perform better than other less than super-ideal stones IRL.

HAHA ur right. I edited it.