Lightscope, Isee2 and Brilliant Scope - Confused

[Lucent]

I am trying to understand the light return analysis used in GoodOldGold website. So far, I am really confused. I pick these 2 stones from GOG website as an example. They both 1.25 Carat, and have the same color so it's easy to compare.

The problem with buying on the Internet is that you don't see the diamond in person. I would not buy stone A for it's Brilliant Scope reading and would not buy stone B for its Lightscope reading.

Can some expert and maybe Johnathan comment on the Brilliant Scope reading and especially the light scope images. Can you tell the different between these 2 stone in term of visual performance?

Looking at the light scope, Stone A light scope image is very round and red while stone B has white V shapes. Stone B also has more black (especially between the arrows) Does this mean that stone B has more fire and stone A is more brilliant?




Stone A: http://www.goodoldgold.com/1_25ct_f_si1_h%26a.htm

1.25, F, SI1

BS: Medium, Very High, Medium
Isee2: 9.8/10

Stone B: http://www.goodoldgold.com/1_250ct_f_vs2__h%26a.htm

1.25, F,VS2
BS: High, Very High, High
Isee2: 9.6/10

Note: The background is darker on this stone

Thank you in advance for all your comment.

 

[Boulder]

Can't help you out on the Lightscope images, but I find that first stone very interesting with that extremely high Isee2 result and not so high Bscope results. I understand that the former measures properties in more diffuse, ambient lighting than the direct lighting measurements of Bscope, but I didn't expect to see such a large difference. Very interesting!

 

[Rhino]

Hi Lucent,

Good questions. My responses will be in bold between yours.

----------------
On 9/11/2003 6:59:56 PM Lucent wrote:
I am trying to understand the light return analysis used in GoodOldGold website. So far, I am really confused. I pick these 2 stones from GOG website as an example. They both 1.25 Carat, and have the same color so it's easy to compare.

Also they are both H&A diamonds as well that feature various results in the LightScope & BrillianceScope analysis PRIMARILY due to the cutting the minor facets. The answers to your questions may require a webpage with graphics to demonstrate my answer.

The problem with buying on the Internet is that you don't see the diamond in person. I would not buy stone A for it's Brilliant Scope reading and would not buy stone B for its Lightscope reading.

No problem. We feature the information so you can make the most informed decision. While those 2 stones do represent a very small fraction of diamonds on the market due to the fact of their H&A symmetry and triple ideal rating if you paruse the diamonds on our website there are H&A stones we feature that do exhibit stronger light return than others under direct light conditions. When you examine LightScope and BrillianceScope results the one factor you MUST keep in mind is that the practical benefits of that critical analysis is how the stone will appear in strong light conditions (ie sunlight, halogens, spot lights, etc.) When you consider that most diamonds on the market do not score anything very high it may surprise you to know that the 2 stones you point out happen to be more beautiful than most diamonds you'll ever see in most jewelry stores.

Can some expert and maybe Johnathan comment on the Brilliant Scope reading and especially the light scope images. Can you tell the different between these 2 stone in term of visual performance?

No. Either of those stones, when compared side by side will be very comparable.

Looking at the light scope, Stone A light scope image is very round and red while stone B has white V shapes. Stone B also has more black (especially between the arrows) Does this mean that stone B has more fire and stone A is more brilliant?

Stone B does exhibit more intense light return through the table due to the blacks and darker reds under the table DUE TO TWEAKING OF THE LOWER GIRDLES. Tweaking the lower girdle facets to certain angles/length will cause light return to be more intense under the table and between the arrows. That is a good thing.


Stone A: http://www.goodoldgold.com/1_25ct_f_si1_h%26a.htm

1.25, F, SI1

BS: Medium, Very High, Medium
Isee2: 9.8/10

This stone above (the 1.25ct F SI1) has "untweaked" lower girdles and therefore the reds are more pale under the table. So while this stone's lower girdles are "untweaked" it's upper girdles happen TO BE TWEAKED.

Hehe... The upper girdles are tweaked in the sense that it has eliminated the white "V" shaped points of leakage that the 1.25ct F VS2 has. When upper girdle facets are cut to certain angles (which are very close to the actual crown angles) blatant leakage (white) is eliminated.

Stone B: http://www.goodoldgold.com/1_250ct_f_vs2__h%26a.htm

1.25, F,VS2
BS: High, Very High, High
Isee2: 9.6/10

Note: The background is darker on this stone

Thank you in advance for all your comment. Hopefully, I will use this knowledge to pick a nice stone for my fiance.

Exactly. The reds under the table are darker and richer due to tweaked lower girdles. What is interesting about this stone is this is an example of JUST THE OPPOSITE of the first stone in that it has tweaked lower girdles but UNTWEAKED upper girdles (which is why the reds are paler around the perimeter).

You can see the results of both in the girdle graph provided with each diamonds MegaScope analysis.

The tweaked upper girdles show a thicker girdle thickness lobing down at the girdle halves (crown side) and the untweaked lower girdles will show greater thickness at the girdle thickness at the bezels.

Currently there are 2 ways of tweaking upper girdles. One tweaks upper girdles for light return. Another is tweaking upper girdles for contrast (both are beautiful effects) and there are positives to either.

You can not see (on a MegaScope report at least) the results of tweaking/untweaking of the lower girdles as you can only see this on hardware/software that measures the lower girdles. We have this and have begun featuring minor facet reporting on some of our stones but until we have our full tutorial up on the minor facets then we'll be providing it with every stone.

This is all stuff I'm working on for my minor facets page but since you asked I thought I'd respond.

Kind regards,
Rhino----------------

 

[Rhino]

Boulder is correct about the Isee2. It's analysis is done under totally different light conditions than the BrillianceScope and represents the stones appearance (not just in direct light) but moreso under the diffuse/ambient light conditions (which most people view diamonds in everyday).

Isee2 results will not correspond with BrillianceScope results for this reason. Plus Isee2 examines optical symmetry and digitally grades it whereas the BrillianceScope does not and that is a major factor in determining value in the make. I have recently updated our BrillianceScope tutorial and am currently working on giving a total breakdown and full tutorial on the Isee2. As soon as it's finished you'll know about it.

Peace,
Rhino

 

[Garry H (Cut Nut)]

I am still trying to understand what these devices "measure" ???

One of these stones is Girdle Cheated - if you look on the website - it has thick parts on the girdle where the bezel / mains meet; there fore the upper girdle facets are steeper than they would otherwise be (by about 4-5 degrees) and that is why the lightscope / ideal-scope leakage shows up so strongly. This is bad and should be picked up by labs and penalised in symmetry or somewhere!!!
It is done for one reason only - to increase yeild and rip people off.

The other stone has 8* 'ACA new line' type tweaking. Some like it, some do not (I do). The bS score on this shows how a stone can fall down if it lights up between the lighting positions of the BS.

Clever cutters and buyers seem to have been able to work out how to cut / buy stones that will give better results.

You might call these BS stones.

 

[Colored Gemstone Nut]

The other stone has 8* 'ACA new line' type tweaking. Some like it, some do not (I do). The bS score on this shows how a stone can fall down if it lights up between the lighting positions of the BS.

Clever cutters and buyers seem to have been able to work out how to cut / buy stones that will give better results.

You might call these BS stones. ----------------

Hi Garry,

When you state "the BS score on this shows how a stone can fall down if it lights up between the lighting positions of the BS", I would like to ask you what experience have you had with the machine. What exactly are the parameters set for the lighting positions in which you have contention. Would there be any relevant factors you might add about sharing any knowledge of the machine and real life circumstances you might have had with clientele. I am just curious Garry

When you have customers in Aulstralia view diamonds what kind of ideals do you market. Are they Hearts & Arrows and is there a preference for the shorter star/larger upper girdle or longer star/smaller upper girdle type. My question comes because being that its a consumers market what are consumers buying based on what you see them preferring with their eyes? B-scope, Lightscope, Isee2 aside...

If you were buying a diamond for your wife besides being a D color and eye clean si-1 what cut style would you choose??

-Josh Rioux
Sitka, Alaska

 

[Garry H (Cut Nut)]

The bS has about 5 light positions where the ring light sits while a photo is snapped. It appears that some nice stones dip out because their light supply camoes from the blank spots.

Look at how the concentric rings appear in the display from this great (very old) MSU / OctoNus website:

http://www.cutstudy.com/cut/english/comp/scint1.htm

If you play with the angles etc you can see how it might be possible to design a cut that would max out on the BrillianceScope.
I have played with the device for a couple of days in a research lab. The guy (laser background) who was using it to design and test new cuts was not impressed. As i say - it measures something - but what?

 

[Rhino]

Hey friends,

Haha... I knew this would generate a response from Gary.

Gary ... while both you and I like the tweaked upper girdles (and I also love the upper girdles tweaked for contrast even more) if we are to take the untweaked upper girdles which are thicker at the girdle bezels and DISQUALIFY them from being ideal because we don't like them, then on the same token we should take the tweaked upper girdles for light return and DISQUALIFY them as well. Why do I say this? For the same reason that beryl had stated in an old dt thread. IT DISRUPTS THE CONTINUITY OF THE GIRDLE. If you look at girdle graphs on both types of stones the girdles get noticeably more wavy at those junctures (bezels and halves) while the upper girdles tweaked for contrast have the best and most consistent continuity and are the most uniform out of the 3 types. I have seen idealscope images of certain popular *brands* that also have untweaked upper girdles but we will not delve there.

IMO the tweaking of the lower girdles play a MUCH more important role than the upper girdles.

In a perfect world ....

Rhino

 

[Garry H (Cut Nut)]

Rhino I can not believe that you would sacrifice light return at the edge of a stone (making it appear smaller) for contrast. The stone that is thick at the bezel mains costs more for the same diameter as well, and runs the risk of being downgraded by the labs - in Europe HRD measure the girdle at this point and will not be fooled.

Re the effect of lower girdle facets - I do not call this tweaking - it is just a simple length issue which can be understood (I hope) from the Ideal-Scope reference chart on the other thread

 

[Lucent]

"One of these stones is Girdle Cheated - if you look on the website - it has thick parts on the girdle where the bezel / mains meet; there fore the upper girdle facets are steeper than they would otherwise be (by about 4-5 degrees) and that is why the lightscope / ideal-scope leakage shows up so strongly. This is bad and should be picked up by labs and penalised in symmetry or somewhere!!!
It is done for one reason only - to increase yeild and rip people off."

"The other stone has 8* 'ACA new line' type tweaking. Some like it, some do not (I do). The bS score on this shows how a stone can fall down if it lights up between the lighting positions of the BS. "


Thank you for responding to my post.

Gary can you please tell me which stone is Girdle Cheated and which has the 8* type tweaking by using stone A or B. Most of us are newbie and can't figure out which is which.

Does tweaking mean cheating?.

 

[Lucent]

Can someone please explain where the bezels meet mains. Is this where the red line is on the girdle graph?

 

[Garry H (Cut Nut)]

Yes - bezels = where the red line is.

 

[Rhino]

Can I post an educational link from my website here teaching our friend about the subject at hand?

Rhino

 

[Colored Gemstone Nut]

----------------
On 9/12/2003 5:21:52 PM Lucent wrote:

Can someone please explain where the bezels meet mains. Is this where the red line is on the girdle graph?
----------------

Hey Lucent...

Hope this helps..

-Josh Rioux
Sitka, Alaska

 

[Garry H (Cut Nut)]

Well explained josh.

The USA labs measure the girdle thickness at the valley - the very thinnest point - not at the red line - which is where the Europeans measure girdle thickness.

It is normal for the red position to be 1.6 or 1.7% thicker than at the thinnest part (which is the missing amount that causes all diamonds to be "warped" according to Fred Cuellar - the pavilion depth, girdle thickness and crown height % on any AGS cert can never add up to the total depth %).
So a girdle cheated diamond will actually be 1 or 2% deeper than you would expect it to be from the Sarin or AGS report.

(HCA will capture a spread penalty for girdle cheated stones - but it will not give a lower light return score.)

But the real damage is done because the upper girdle facets are way too steep causing light leakage. This light leakage will appear as darkness once the stone is set. Rhino is saying this darkness = better contrast or scintillation (which is true) but this comes at a great cost in extra weight and reduced light return. The diamond looks smaller because the outer facets are not working and the stone weighs more per mm spread.

 

[Rhino]

No No! Gary... I am not saying that the cheated girdles are causing greater contrast (upper girdles around 44-47'). I am saying that upper girdle angles around 40-42' give the best contrast. A diamond with this LightScope image/upper girdle angles.

rhino

 

[Garry H (Cut Nut)]

Sorry rhino - i thought you said you liked the stone with the thicker main bezel and steeper upper girdles?

 

[Rhino]

No prob mate. If I had my choice I'd prefer upper girdles either of the 35-39 degree range (tweaked for light return) or 40-43 degree range (tweaked for contrast). However sometimes there are hard to find stones on the market and everything about the stone is sweet with the exception of perhaps the upper girdles tweaked for weight. I have to weigh all factors when making a purchasing decision and if the only negative about the stone is upper girdle angles a touch steeper than I prefer I wouldn't throw it in the dog house.

You know what I'm sayin bro.

Rhino

 

[Lucent]

Thanks to Johnathan and Garry for the informative posts. However, on the same stone's megascope,

Johnathan wrote:

"Tweaking the lower girdle facets to certain angles/length will cause light return to be more intense under the table and between the arrows. That is a good thing."

Gary wrote:

"One of these stones is Girdle Cheated - if you look on the website - it has thick parts on the girdle where the bezel / mains meet; there fore the upper girdle facets are steeper than they would otherwise be (by about 4-5 degrees) and that is why the lightscope / ideal-scope leakage shows up so strongly. This is bad and should be picked up by labs and penalised in symmetry or somewhere!!! It is done for one reason only - to increase yeild and rip people off."

Lucent writes:

"Confused...."

Both are gemologists. Johnathan has seen this stone but he is also a saleman.

I have trouble understanding how the word bad is used to describe an IDEAL stone? Both stones have HCA score

Johnathan, You're top on my list for consideration (as vendor) - so I am asking a lot of questions

Gentlemen, thank you for your response

 

[Garry H (Cut Nut)]

The only way HCA can detect these stones is sometimes the girdle will show up as overly thick from the entered data.
if that ever happens - Beware

 

[Lucent]

Garry,




Nice picture. Look less serious than the last one with suit and tie - but no less handsome.




Would you kindly post a simulated Ideal-Scope image of the two stone please. I would like to see what it look like under the ideal scope. Not too many people have a lightscope so I don't really have anything to compare to.




Thanks in advance.