How significant are the star facets and lower girdles info?

[JohnQuixote]

Date: 8/5/2005 10:02:21 PM
Author: Midnight

I would guess ''white light return''. Thus, the BS should correllates with a lower white light return on your LightScope example ''Minor Yaw'' vs. ''Virtually no Yaw'' since the ''Minor Yaw'' shows more pale red areas. Of course, this is assuming that the pale red areas are due to the yaw and not because if there are differences between crown & pavillion angles between the two examples.

I’ve got to hand it to you Midnight. Understanding that angle variance (or a myriad of other backlit issues) could be what Rhino interpreted as yaw puts you at the front of the class.

Nice job.

 

[JohnQuixote]

Here is a lesson in scope lighting and the elegance of the H&A Viewer for viewing facet construction.

1. The beauty in a round diamond is that it creates so many reflections. This multiplicity is what causes its great sparkle but beware, as it also convolutes assessment of the basics.

Here are wireframe diagrams. One shows a simple diamond wireframe. The next shows multiple reflections as they appear in a diamond with PERFECT patterning. In one without perfect patterning (most diamonds on the planet) the reflections are more random, convoluted and hard to interpret.

 

[JohnQuixote]

2. Ideal-scope, ASET and Rhino’s lightscope use backlighting (light from beneath, reflectors from side, obscured from top). They show light performance dynamics with similar multiple reflections.

Here are ideal-scope views. Compare to the wire frame with reflections above see that IS is subject to multiplicity too. At 2 degrees tilt even a perfectly patterned diamond becomes convoluted.

 

[JohnQuixote]

3. The Hearts & Arrows viewer is inert from behind. It is lighted only from above and sides. You can observe construction in one side of the diamond without interfering multiple reflections from the other. At 2 degrees tilt there is still convolution but nothing like the backlit view above in the ideal-scope under the table.

Compare the arrows views from H&A viewer with Ideal-scope above. It is much simpler to see actual fundamentals of construction without multiple reflections in the H&A viewer because it's not backlit.

 

[JohnQuixote]

4. Finally, to illustrate the difference in multiplicity, here is what a pavilion would look like in ideal-scope or lightscope versus a H&A Viewer.

We''d never use this, as it''s operating in reverse of light dynamics, but I think this clearly shows why you must use a H&A viewer to get a clear picture of pure pavilion construction. It’s an elegant tool without obstruction.

Another bonus to the pavilion view is that it never has distortion from tilt, because the diamond sits on its table. It’s automatically leveled for you. You have 8 mains and 16 lower girdle facets. It’s an unobstructed view of what’s happening without interference from what is going on above.

You should not assess diamond construction with everything jumbled all together. Technology is great but sometimes the simple view is the best one.

 

[JohnQuixote]

Date: 8/5/2005 5:25:33 PM
Author: strmrdr

Which brings me back to the question I asked John in a round about way.
How much yaw is too much?

I know you love concrete answers Strm. Brian identified it less than a decade ago and it can't be readily understood by one who has not sat at the wheel.

There are no numbers by which to judge it. Maybe helium will help.

The only way to safeguard against yaw is to adopt visual standards. At the IDCC in Moscow Brian presented a grading system for H&A. It was hoped that laboratories and peers would unite to maintain higher standards for manufacture as they have in Japan where the standard was set. In the absence of adoption by labs or peers Brian developed his set of guaranteed ACA standards for the company to protect consumers. It safeguards against yaw, prescribes the most visually balanced minor facet combinations and many other things.

Not every pattern will look exactly alike but if you have a set of standards you can maintain consistency. If you see a diamond with a lot of azimuth shift there is usually yaw in the pavilion facets, but you need a hearts view to tell. What do we think is too much? Look again at the true hearts images I posted on page 1. Those are acceptable by Brian’s standards. The fact that there is NO yaw is simple and obvious. It passes everything on the checklist of Brian’s guarantee.

If there were a set of numbers or a grading system EVERYONE would adopt (hint hint) it would be easier to say “That hearts pattern is T, NT or Non (True, Near True or Non-True).”

For now the absence of yaw = no opportunity for adverse effect.
It’s like making sure we’re not even ‘a little bit’ pregnant.

It's ongoing. The examples on page 1 are archived - some years old - but here is the hearts image of a 1ct E VVS1 ACA we sent to a customer a few days ago, along with its ideal-scope. No yaw. No worries.

 

[JohnQuixote]

As for future potential to gauge this: Brian and Bruce are working on it and AGS is developing a metric that handshakes with this assessment having to do with dynamic fire & dynamic contrast. What we DO know is that yaw influences the character of a diamond’s beauty, so to be safe Brian minimizes yaw to the maximum, in line with the grading standards we adhere to.

No yaw = no opportunity for adverse effect.

 

[JohnQuixote]

Date: 8/5/2005 5:21:01 PM
Author: Rhino


One thing you keep reiterating John which I would also take issue with ... 'It's all in the hearts' ...

Ah. But my good Rhino, it is “all in the hearts.”

There are many sellers, you included, who might consider breaking away from old world thinking on this count. Diamond cutters are tricky and will get the better of you if you don’t see it from their POV.

Garry was the first girdle crusader who shared with the community how things could be swindled and altered to save weight and disguise error. Brian’s illustrations of how “it’s all in the hearts” takes that kind of thinking to the “heart” of the matter.

The crown view is understandably Ptolemic. The geocentricity of observable end-use creates a paradigm not easily shifted, especially for sellers. Diamond cutters, however, are more heliocentric in their focus on the engines that drive light return.

Right now you are playing Ptolemy to Brian’s Copernicus.

Consider all of the performance issues that rely on the pavilion.

1. The pavilion mains (the engines driving light return)
2. Patterned alignment of mains and lower girdles (creating optimization of light return)
3. LGF percentages (creating balance through a range of light conditions)
4. Absence of yaw (unobservable in the crown, crucial to optimization and balance)

In all teaching – from math to English to music – solid FUNDAMENTALS are the foundation on which the end-product is built. Alphabet, Numbers, Notes & Rhythms. It is no different here. Pavilion construction is the end-all be-all. It is the foundation upon which light performance is built. Everything else is icing on the cake.

The fundamental principal of Eightstar’s cutting is dedication to the eight main pavilion facets that are their namesake. Without perfect alignment and limited yaw they can’t achieve their no-leakage footprint. So it is with A Cut Above. So should it be with any committed to fundaments of cutting to perfect symmetry.

Of course crown analysis is an important test-drive for sellers. We place emphasis on it as a final check, but failure to recognize the importance of the pavilion view is the reason no one gained understanding of ‘Gavin’s yaw’ before Brian, a cutter, identified it. Our primary focus here in the offices is the PAVILION.

Rhino, as an enlightened colleague we urge you to adopt the “all in the hearts” philosophy. The crown-down analysis is nice as end-use assessment for clients, but if you want to be an authority you should realize that the pavilion is the starting point where the performance and beauty in a diamond is created.

Brian has been illustrating this since 1998 and published material on another forum as long ago as 2000. I’m surprised you have not adopted this philosophy yet while other cutting houses HAVE and are producing more beautiful, well-patterned diamonds as a result.

 

[JohnQuixote]

Date: 8/5/2005 5:39:25 PM
Author: Rhino
Just wanted to address this comment John.

(C) Now consumers are aware of minor facets, but because measuring devices aren’t accurate they stand to get bad information.

I understand your basis for saying this as most scanners do not have the ability to produce the precision we are talking about ... HOWEVER ... this Rhino is not your average bear.

Here is the actual picture of the stone I was posting about (with the yaw) except I've lightened the colors to match the graphic produced by GemAdvisors 'idealscope' view.

Take careful note of the patterning under the table as you compare the image produced by the model vs the actual shot of the diamond under LS. I oriented the pictures so they are in the exact azimuth.

In my prior post last night I had stated

3. An *accurate* Sarin 3d model imported into DiamCalc whose results can be observed via...
4. Gem Advisor.

I think you misunderstood me John becuase I did not say that Sarin or OGI *measures* facet yaw. I was simply stating that we can see the effects of this through accurate modeling as presented in the graphic below. The duplication from the model of the actual image is ... well ... fricken IMPRESSIVE. Wouldn't you agree?

Rhino, I agree that it is impressive for a simulation but it doesn’t change your flawed assessments about yaw. Finding yaw in this diamond was done using the tiny hearts view you posted. Your lightscope image is nice but doesn’t tell anything about yaw. The GemAdvisor tells less.

Though it’s remarkable how far we’ve come (it is a fun image to nitpick), the GemAdvisor and lightscope have several obvious differences.

1. The arrowhead under the bezel is shaped differently. Bad main scan?
2. Differences in these distortions, both in degrees of hue and shape.
3. You identified this as yaw in your example (we know that’s not correct). Why does DC look so different though? Any guesses?
4. Same question as 3.
5. The girdle evaluation is different. Scanning problems again? (not picking up polishing techniques?)
6. Where did that yellow come from in the GemAdviser file?

I’m sure we could pick out others. I’d never accept it as a substitute for analyzing actual diamond images... But as a supplement, yes.

 

[Dancing Fire]

John Q
so.....all ACA stones guarantees no yaw at all? am i right?

 

[JohnQuixote]

By the way Rhino,

Do I think a reflector view (lightscope) is valuable for overall light performance asessment? Yes. I’ve always said that... That may be what you’re getting at but from a yaw-education standpoint it isn’t relevant. You cannot identify yaw with the crown view.

I do want to say that your exploration of devices (even to the point of overhype causing some error here) is the reason I think your personal assessment of Brilliancescope images is useful to your specific clients. I say that with all respect - even though I take issue with the Brilliancescope images you posted in this thread.

Someone running Brilliancescope for a chain store who was working at Orange Julius last week can’t possibly tell anything meaningful with it until it’s completely repeatable. With great power comes great responsibility, right Spidey? I will not be a BS pundit until it is completely repeatable and they answer some other important questions. The right questions are now in their FAQ, but not all the answers are there.

In the hands of an expert who does not oversell it, Brilliancescope provides appealing information that may be considered a piece of the puzzle for assessing diamond performance. It is nowhere near as valuable as actual imagery though. It is a GREAT sales tool.

In keeping with this, I think 3D scans are a nice reference for trade experts who have actual diamonds in hand as a means of correlation and ‘reality check,’ but enthusiasm seems to be carrying some people too far. It becomes a matter of seeing what you want to see, rather than seeing what’s really there. We will see what the future and ETAS bring us. Serg and his team are quite brilliant.

What excites me a lot about 3D modeling as it exists now is the ability to develop proprietary cuts.

 

[JohnQuixote]

Date: 8/6/2005 12:15:22 PM
Author: Rhino
Midnight and strm ... you guys win the boobie prize!

Here are the Bscope results on each. This is a good example of how fine we can split the hairs in our lab.

Let me make a note here too while I''m at it. 2 stones that score triple VH''s and for that matter even 2/3 vh''s are virtually impossible to distinguish with the human eyes. As I stated earlier we are examining criteria that goes beyond human eye observatoin.

I’m sorry Rhino, but this Brilliancescope example you’ve given is completely invalid relative to yaw.

In any experiment you must have a control subject that is identical to the test subject. Even if you had identified yaw correctly, you are not comparing apples to apples. You need 2 diamonds of the same size, with the same angles and the same table percentage – one with yaw and one without. Do you see what I''m saying?

Strike this comparison from the record please, kind sir.

 

[JohnQuixote]

Date: 8/6/2005 12:30:49 PM
Author: Rhino

Good question Rock.

In the examples provided we are observing results in light transmission through the table. This is the area showing us the most obvious differences. So in this case the minor facets (lower girdles in this instance) are or should be functioning as mirrors as opposed to windows with the table functioning as the window in which the light is exiting. From my personal studies yaw is more easily detected under the table in the face up view than in any of the other crown facets (bezels, stars, upper girdles). The reason it is easier to detect under the table is because the table gives a clear view to the pavilion with no other facet distraction and allows you to observe optical symmetry under the table unobstructed.

Stop the madness!

There is certainly not a clear view to the pavilion through the table. The crown of the diamond is so lively because of all the reflections from multiple facets are directed through the crown. The only way to understand what is happening in the pavilion is to view it from the back and with a very simple tool.

Once you look at the pavilion and fully assess construction with the ABILITY to observe the mains - then look to the crown to see how it all comes together. Or don’t bother to tackle yaw.

 

[JohnQuixote]

Date: 8/5/2005 6:08:50 PM
Author: Rhino
Just wanted to answer/comment here.

Date: 8/5/2005 2:35:15 AM
Author: JohnQuixote

It's exciting that these recent threads have begun, since Brian introduced this information years ago and has been patiently waiting.

Surely I don't read the forums as much as I'd like. When did Brian introduce this information?!? I've been observing the effects of this too since late 2000 mid 2001 but never quite put into words the whole phenomena. Of course I'd be interested to see what Brian has written on it.

You might not have been able to put it into words since it isn’t yaw, but a jambalaya of other things.

Brian has been putting forth hearts patterning information since before PS. You would have seen it on another forum. It’s likely in those archives – a whole treatise on hearts patterning. Others, including perhaps you, were more focused on crown particulars when he put it forth.

Remember that Brian identified and coined the term yaw (still called ‘Gavin’s yaw’ by some). It would be good for you to arrange a time to speak to him about the fundamentals. You’re confusing yaw with azimuth shift. It takes unconventional 3 dimensional thinking along with an understanding of graining and tricks cutters use to get a facet to run. Even Garry, who has far more experience than you or I, had to exchange dozens of emails with Brian, Paul and Bruce to get where they were coming from.

Lightscope and H&A Viewers

I suspect only the crown of the diamond is surrounded by reflecting material in your lightscope, correct? If this is so, a 3D view of distortions and angles of incidence is not possible in the pavilion. Even if it's not so, the pavilion view is the only view that fully discloses yaw. Do you have examples of what you are taking about?

Correct. Only the crown. Examples provided in previous post of mine. I am more concerned with the *face up* effects of yaw moreso than what I can see on the pavilion (although I am noting your examples with great interest) and is the primary way in which I believe it should be analyzed. If yaw is present but does not affect face up appearance then I think it's a waste of time anayzing. hehe

It does influence, at the very least, the character of diamond beauty.

I imagine it's possible to assess reduction of optimization (less robust and even light return) and some stray reflections DUE to yaw in lightscope. This is also possible with ASET and Ideal-scope.

I've tried to photograph it through ASET and IS. If I worked on it I'd probably stand a better chance of getting it through an IS but in the ASET's that have been distributed so far ... NO WAY can it be photographed through the handheld. I'm awaiting our desktop ASET which should be here any day now and I'll see if it can be done through it but i'm not holding my breath.

Agreed on all counts.

Jon, you may be interested to know that yaw can be responsible for some of your 'hot spots' on BS, so it's rewarding an undesirable diamond quality.

While on that topic, diamonds with LGF > 80% are also rewarded by BS, even though they are not as visually balanced through a range of lighting as those with LGF just under or at 80%

Not true on both accounts bro. Hot spots are produced primarily by lengthening lower girdle facets not the presence of yaw. I would also note that when anal retentive clients *compare* H&A diamonds side by side in direct lighting ... guess which wins out 90% of the time? And this is before they even see or learn anything about a BrillianceScope! The visual balance is nothing short of spectacular in a precision cut stone with 80-82% lgs. Matter of fact I purposefully look for them.

Again that fundamental understanding of yaw relates to this. We tested BS for a year. Brian’s evidence about yaw and hot spots agrees with what you’re saying but you can now revise your understanding.

When Brilliancescope’s spotlights hit yaw in a main that light gets skewed and sent elsewhere. It’s a hot spot of light showing up in an unexpected place. By lengthening the lower girdles you narrow those mains, so the areas with yaw reflect even more thinly focused ‘hot spots’ in unintended places. Yes, lengthening lower girdles exaggerates the effect. I believe you’re saying the same thing, just not identifying it for what it is.

Sure. I don't mind peer review and YES it is a good thing. I respect Brian's research and if he doesn't mind I'd like to review his material as well and compare notes.

Lest any think I am Rhino-hunting, I'm not (and besides, he has thick skin)

I want to be clear that I think highly of Jonathan and his enthusiasm for all aspects of dia-knowledge.

I appreciate that man. I respect you and the ladies and gents over there too bro! From what I'm gathering we're all on the same page here, just arriving through different means/methods.

Peace out,

I do think a convo is in order, but it may take more. Anyone who has not spent years cutting or faceting has had to have a 3D, physical interpretation of this to assimilate how it is couched inside of traditional thinking. Even cutters who have been in this business for decades have a difficult time interpreting even the cause of yaw, much less all of the ramifications. It's just not something that is easily quantifiable.

 

[JohnQuixote]

Date: 8/5/2005 6:08:50 PM
Author: Rhino

Not true on both accounts bro. Hot spots are produced primarily by lengthening lower girdle facets not the presence of yaw. I would also note that when anal retentive clients *compare* H&A diamonds side by side in direct lighting ... guess which wins out 90% of the time? And this is before they even see or learn anything about a BrillianceScope! The visual balance is nothing short of spectacular in a precision cut stone with 80-82% lgs. Matter of fact I purposefully look for them.

(edited)

Cool. Shifting gears here...Your statement about 80%-82% lower girdles winning out in direct lighting makes my further point about Brilliancescope very clear.

Lower girdle lengths

Long LGF = >80% (narrow mains)

High direct light performance.

We know very well that in bright lights lower girdles >80% enhance diamonds. When they are that long the pavilion mains are very narrow, so they thin and intensify bright light, especially spotlighting like jewelry store halogens. The bright, direct lighting chamber of a Brilliancescope also rewards lower girdles >80% because of that narrow, intensified return. However, if you look at the hearts patterning you see that lower girdles >80% have notable splits in the Vs, reducing optimization, and creating less surface area for the pavilion mains – which are the engines that drive light return. Under halogen spotlights such narrow, intense return makes them appealing but the trade-off in our view can be less performance potential in other real-world lighting conditions.

There is nothing wrong with these diamonds. There are reasons for cutting them this way. They are beautiful and there is demand among consumers for them. In head-to-head direct light they're winners, as stated.

Short LGF = <76% (thick mains)

Many consider Eightstar diamonds to be among the most beautiful, yet they perform horribly on Brilliancescope. Why? The lower girdles are around 75% and don’t have the narrow, intense light return the Brilliancescope favors. No one of sound mind would argue the fact that Eightstar is one of the best performing diamonds in soft light like candlelight. Very logical. It’s due to the 75% lower girdles (their approximate design for minors). Very thick pavilion mains with large surface area, so soft light is picked up and returned better. Eightstar has a distinctive look. Some people don’t like the way they perform in direct light as much as other diamonds or the thick look of the arrows with contrast. Again, logical.

In a blind test Eightstars may get ‘beat’ side by side in direct light (been there) but they typically ‘win’ in soft light with broadfire flashes you can see across a restaurant. There is demand for this style as well.

Medium LGF = 77-80%

Lower girdles in the 77-80% range are in between. Our personal experience revolves around targeting this length. Of course we feel the hearts patterning is crucial, as it determines the performance potential of the diamond before you ever see it in the face-up view. When there is complete optimization of light return with no yaw we have found this length can provide optimum performance in direct light and soft lighting as well.

Almost all diamonds sparkle well in bright jewelry store lights. This is because the sheer volume of light returned to the eye overpowers fine-tuning of the cut such as we are discussing. In diffuse lighting and soft conditions like candlelight the minor facet particulars and how well the mirrors are focused and aligned with each other (patterning) becomes evident.


Taste varies for rounds. These nuances are very slight. There are many beautiful configurations.

For 'ideal' cuts we believe in major proportions near Tolkowsky’s, with a slightly steeper crown to enhance dispersion and scintillation through contrast. True hearts patterning with absence of yaw that aligns all mirrors in the pavilion for optimum light return. Crown patterning that logically follows the fundamentals of the all-important pavilion. Relative to this thread, our minor configurations are lower girdles in the range of 77-80% and stars from 48%-51% that empower performance in direct light and soft light. This can be the best of all worlds in our minds and is what caused Brian to coin the term Visual Balance™.

This does not prevent other configurations from being as beautiful. This is our approach, topical to the thread and in response to discussion about Brilliancescope readings for long LGFs. We are not saying one is the best. There are many ways to cut a diamond and many different appreciations for beauty. We are able to produce our own goods, and we do so according to our philosophy and our taste.

 

[JohnQuixote]

Date: 8/7/2005 9:09:45 PM
Author: Dancing Fire
John Q
so.....all ACA stones guarantees no yaw at all? am i right?

That's the intent. Brian says there is not one diamond out there without some form of yaw, but if it doesn't show in true hearts patterning it is inconsequential.

In the absence of a metric or universal standards it is currently a visual check as we have discussed in this thread.

ACA Guarantee

1. Lab grade of Ideal in symmetry
2. Lab grade of Ideal in polish
3. Lab grade of Ideal in light performance
4. Lab grade of Ideal in proportions

5. Uniformity and symmetry in both hearts and arrows patterns (yaw and patterning are checked here)
6. Pattern is well centered (patterning checked here)
7. No broken, split or significantly different sized hearts (yaw and minor facet relations checked here)
8. Hearts slightly separate from arrowheads above (minor facet relations checked here)
9. No misshaped arrowheads, broken shafts or misalignment of shaft to head (patterning and yaw checked here)
10. Arrow points all meet the girdle (patterning checked here)
11. No distortions caused by facet yaw (yaw checked here)
12. No unevenness caused by extreme variance (patterning checked here)


Just like 'flawless' diamonds have imperfections under very high magnification, this is not a simple matter. It's about how the cutter gets the facet to run on the wheel. It's definitely possible for yaw to be so slight it's imperceptible.

 

[JohnQuixote]

Date: 8/5/2005 10:47:01 PM
Author: RockDoc


Interesting subject.

But I''d like to ask both of you...... in pondering Storm''s question, I wonder the same thing.....but with a bit of a twist.

Since the minor facets are sort of the windows, one would think that the amount of the yaw would influence the exit path of the light, so is there a loss of light through the exit path, or is it just directed at a different angle?

Rockdoc

Rock,

We can look to the hearts patterning for origins. In yaw that is not detectable by Sarin/Ogi the angular path of the light is just redirected but not observable due to obscuration. Severe yaw can cause escape (a more scientific term for leakage), but this is also detectable as azimuth shift or just plain poor cutting. It’s a double edged sword. Whether the angles or correct or not often determines what opens them as windows in relation to the viewer’s eye. Remember that diamonds are viewed dynamically, not in static view.

Interestingly, Brilliancescope’s hot spots are one way to detect where that light may be going. When we tested Brilliancescope this is one thing Brian liked about it – the photos. Unfortunately, this is a reward of yaw which is not appropriate in the book of puritanical cut.

 

[Midnight]

Date: 8/7/2005 9:38:35 PM
Author: JohnQuixote

Date: 8/5/2005 6:08:50 PM
Author: Rhino

Not true on both accounts bro. Hot spots are produced primarily by lengthening lower girdle facets not the presence of yaw. I would also note that when anal retentive clients *compare* H&A diamonds side by side in direct lighting ... guess which wins out 90% of the time? And this is before they even see or learn anything about a BrillianceScope! The visual balance is nothing short of spectacular in a precision cut stone with 80-82% lgs. Matter of fact I purposefully look for them.

Cool. Shifting gears here...Your statement about 80%-82% lower girdles winning out in direct lighting makes the further point about Brilliancescope very clear.


Lower girdle lengths and balance



Long LGF = >80% (narrow mains)

Why do cutters like to fashion long lower girdles? Two reasons: Weight retention and sales.

We know very well that in bright lights lower girdles >80% sell diamonds. When they are that long the pavilion mains are very NARROW, so they thin and intensify bright light, especially spotlighting like jewelry store halogens. The bright, direct lighting chamber of a Brilliancescope also rewards lower girdles >80% because of that narrow, intensified return. We think this is deceiving to consumers. As you clearly see in hearts patterning (“it’s all in the hearts”) lower girdles >80% have notable splits in the Vs, reducing optimization, and creating LESS SURFACE AREA for the pavilion mains – which are the engines that drive light return. Sure, under halogen spotlights such narrow, intense return makes sales but the trade-off is less performance potential in other real-world lighting conditions.

So why don’t cutters shorten those lower girdles? It’s because the longer the lower girdles are the closer they are to the main pavilion angle, but the minute you shorten them you are polishing away more weight. It’s the age-old game of weight retention at the expense of performance.

Short LGF = <76% (thick mains)

Many consider Eightstar diamonds to be among the most beautiful, yet they perform horribly on Brilliancescope. Why? The lower girdles are around 75% and don’t have the narrow, intense light return the Brilliancescope favors. No one of sound mind would argue the fact that Eightstar is one of the best performing diamonds in soft light like candlelight. Why? Very logical. It’s due to the 75% lower girdles (their approximate design for minors). Very thick pavilion mains with large surface area, so soft light is picked up and returned better.

It costs Eightstar more weight, but they have a notable footprint. Some people don’t like the way they perform in direct light as much as other diamonds. Again, logical. In a blind test Eightstars may get ‘beat’ side by side in direct light (been there) but they typically ‘win’ in soft light with broadfire flashes you can see across a restaurant.

Balanced LGF = 77-80%

We strongly feel lower girdles in the 77-80% range represent the best balance. It costs a little more weight when cutting, but this minor facet axiom, coupled with no yaw for complete optimization of light return, provides performance rivaling the best diamonds head-to-head in direct light and soft lighting as well.

Almost all diamonds sparkle well in bright jewelry store lights. This is because the sheer volume of light returned to the eye overpowers fine-tuning of the cut such as we are discussing. In diffuse lighting and soft conditions like candlelight the minor facet particulars and how well the mirrors are focused and aligned with each other (patterning) becomes evident.


Taste varies for rounds. Some people like long LGF as you see in many places. Others like more rare, short LGF. Still others like 60% tables and some people don’t like rounds at all.

There are many combinations for beauty and we understand that, but in order to achieve balance we feel this is what you need:

Major proportions near Tolkowsky’s, with a slightly steeper crown to enhance dispersion and scintillation through contrast. True hearts patterning with absence of yaw that crisply aligns all mirrors in the pavilion for optimum light return. Crown patterning that logically follows the fundamentals of the all-important pavilion. Lower girdles in the range of 77-80% and stars from 48%-51% that empower blazing performance in direct light and robust performance in soft light. That is what we call Visual Balance™.

It is the best of all worlds in our minds.

Though well-known to cutters, this information rarely makes its way into the mainstream because simple weight retention and sell-ability drive the machine. Sellers have easier access to LGF >80% because they are far more common, thanks to weight retention, and consumers don’t know the difference.

Hi John,

I knew the "Knight" would be charging back

! You hinted that for perfect "Visual Balance" in WF''s opinion, the star facets should be around 48%-51%. Can you please elaborate on the pros and cons if it wasn''t within this range in terms of optical performance?

 

[Dancing Fire]

Date: 8/7/2005 9:38:35 PM
Author: JohnQuixote


Short LGF = <76% (thick mains)

Many consider Eightstar diamonds to be among the most beautiful, yet they perform horribly on Brilliancescope. Why? The lower girdles are around 75% and don’t have the narrow, intense light return the Brilliancescope favors. No one of sound mind would argue the fact that Eightstar is one of the best performing diamonds in soft light like candlelight. Why? Very logical. It’s due to the 75% lower girdles (their approximate design for minors). Very thick pavilion mains with large surface area, so soft light is picked up and returned better.

true....my SIL''s 8* (fat arrows) do very well in dim bar lights,big flashes,but in direct lights, is just okay.

It costs Eightstar more weight, but they have a notable footprint. Some people don’t like the way they perform in direct light as much as other diamonds. Again, logical. In a blind test Eightstars may get ‘beat’ side by side in direct light (been there) but they typically ‘win’ in soft light with broadfire flashes you can see across a restaurant.

Balanced LGF = 77-80%

We strongly feel lower girdles in the 77-80% range represent the best balance. It costs a little more weight when cutting, but this minor facet axiom, coupled with no yaw for complete optimization of light return, provides performance rivaling the best diamonds head-to-head in direct light and soft lighting as well.

John Q
have you ever tested ACA on the B-scope? i agree, B-scope is good infor,not the deciding factor for purchasing a stone.

 

[JohnQuixote]

DF - It''s a matter of taste, but we agree with you.

We had Brilliancescope for a year. Rockdoc appraises ACA and he runs them on his fairly regularly.

 

[Regular Guy]

Ummmmm...........

 

[Regular Guy]

John, you’ve been working hard. You, too, Johathan.

Unless I’m mistaken (and ultimately, I must at least be partly so), I wonder if these recent discussions haven’t led you to think differently, John, about the visual implications of the patterning done on ACAs in particular, and so, the impact of H&A altogether. For example, not too long ago, I think that, mindful of (was it GIA) reporting that this patterning didn’t earn “extra credit,” you suggested it could be likened to VVS characteristics for clarity. So, if there is a change, is it one of clarification?

For me, and many, value can be attributed to what we can see, and what we are therefore willing to spend on the incremental difference seen. I really think many of us can benefit from the metric I suggested at the end of the thread I started: Mapping the Beauty of a Diamond. Of course, I am just a regular guy, and this “mapping” is really all of what the experts at GIA and AGS have been about for some time now. But for us pro-sumers who need to decide how to spend our hard earned money…giving detail to the visualization of the third standard deviation on a bell curve can mean all the difference. For example, certainly prices have gone up, but the ring I purchased for my wife, based in large part on a knowledge of expected performance extrapolated from the HCA alone, having paid in the neighborhood of 2/3 of what an ACA commands…I could do well to have some additional perspective on the meaning of the difference.

I’m not sure how shopping practices may need to change, if they need to change at all. Although diamonds can be ordered up from WF and your colleagues and sent to an independent appraiser…they are largely seen in isolation in that appraiser’s office, and it’s difficult to understand how such an environment, if one were to seek to engineer its optimization, could be re-engineered to better serve the purpose. Nevermind what either a typical or extra-ordinary appraiser could be expected to bring to the table, where those additional thousands of dollars, in a rationale world, would seek to be justified…. Without having not two, but many alternatives to compare that special one to, it’s hard to see that the independent appraiser, as we routinely have them, is able to provide an “ideal” environment in which to consider the choice at hand.

 

[JohnQuixote]

Ira,

LOL, you are right about workin'' hard. For some of us it''s second-nature.

No different thinking here. I am expressing minor particulars which have always been of KEY importance to us. Brian has been custodian of these designs since the 90s. My elaboration on them is affording you the opportunity to peek into my brain, and the philosophy that drives Brian to have those specific designs cut for ACA after study of many configurations. Lest is be misconstrued, the designs I describe are merely to OUR taste. If someone else who cuts, Paul for instance, would like to offer opinions on design that would be fabulous. I am sure Rhino and others will offer what different configurations they seek, and why.

As for the impact of H&A, it’s a niche market as we all know. Since perceptions vary, I don’t push H&A on people, but will provide the information about why many people find them to be special, (myself included). Everyone knows the majors. The minors are where character in a diamond is developed, thus the elaboration in this thread.

With H&A it comes down to a matter of perception, personal taste and values. On a casual level any diamond that is well-cut is going to be wonderful, plain and simple. Among the millions of diamonds walking the globe you may rarely compare or care about the optimization or ‘subtle insight’ that precision patterning offers.

Likening it to color or clarity is fine. Some people are more sensitive than others.

Those who have made an informed decision to buy a H&A diamond might say they are worth the premium and that they see the subtle differences outlined here. Those who have made an informed decision not to buy a H&A diamond might say they are not worth the premium and that they do not see the subtle differences outlined here. Both can be telling the truth.

‘Experts’ also fall on both sides of the line.

Some say it’s an acquired taste. Was it an ‘acquired taste’ for me? No sir. I knew immediately there was something that appealed to me in patterned diamonds beyond the others I was seeing back as a consumer. It’s why I am in the trade now (you know the story). Differences I have outlined above were evident even without understanding them back then. Eventually I learned the reasons. Today, as I work among hundreds of these diamonds and study minute differences in patterning & minor facet construction, the distinctions stand out even more.

 

[JohnQuixote]

Date: 8/7/2005 11:13:05 PM
Author: Midnight

Hi John,

I knew the ''Knight'' would be charging back

! You hinted that for perfect ''Visual Balance'' in WF''s opinion, the star facets should be around 48%-51%. Can you please elaborate on the pros and cons if it wasn''t within this range in terms of optical performance?

Charging back indeed. Nothing like being in giddy-up mode.

Our prescriptions for stars exist to eliminate leakage near the girdle. Remember that the stars determine the length of the upper girdles. Stars too long result in short upper girdles with upper girdle angles too steep. Stars too short have the opposite effect, and the lower girdles are too long. The 48%-51% configuration is the best combination for us with regard to balance between stars and uppers and our ability to minimize leakage and maximize performance.

 

[Garry H (Cut Nut)]

Date: 8/8/2005 3:05:33 AM
Author: JohnQuixote

Those who have made an informed decision to buy a H&A diamond might say they are worth the premium and that they see the subtle differences outlined here. Those who have made an informed decision not to buy a H&A diamond might say they are not worth the premium and that they do not see the subtle differences outlined here. Both can be telling the truth.

‘Experts’ also fall on both sides of the line.

Me, I am just a regular bloke

Its all 2 much 4 me

 

[mkb]

me too gary,
John just tell me how to cut them

luc

 

[Regular Guy]

Date: 8/8/2005 3:05:33 AM
Author: JohnQuixote



Ira,


As for the impact of H&A, it’s a niche market as we all know. Since perceptions vary, I don’t push H&A on people, but will provide the information about why many people find them to be special, (myself included). Everyone knows the majors. The minors are where character in a diamond is developed, thus the elaboration in this thread.

With H&A it comes down to a matter of perception, personal taste and values. On a casual level any diamond that is well-cut is going to be wonderful, plain and simple. Among the millions of diamonds walking the globe you may rarely compare or care about the optimization or ‘subtle insight’ that precision patterning offers.

Likening it to color or clarity is fine. Some people are more sensitive than others.

Those who have made an informed decision to buy a H&A diamond might say they are worth the premium and that they see the subtle differences outlined here. Those who have made an informed decision not to buy a H&A diamond might say they are not worth the premium and that they do not see the subtle differences outlined here. Both can be telling the truth.

‘Experts’ also fall on both sides of the line.

Some say it’s an acquired taste. .......

Well, I''m not sure I''d want to back off too far. One out of two Pricescrope independent appraisers will tell you that H&A precision patterning is either what allows them to call a diamond ideal or super ideal. I know; I read it here!

So it''s not just like it''s your little thingy. Still, the question of strategies for giving meaning to the measure remain, for me.

Regards,

 

[strmrdr]

Date: 8/8/2005 3:26:29 AM
Author: JohnQuixote

Date: 8/7/2005 11:13:05 PM

Author: Midnight


Hi John,


I knew the ''Knight'' would be charging back

! You hinted that for perfect ''Visual Balance'' in WF''s opinion, the star facets should be around 48%-51%. Can you please elaborate on the pros and cons if it wasn''t within this range in terms of optical performance?

Charging back indeed. Nothing like being in giddy-up mode.

Our prescriptions for stars exist to eliminate leakage near the girdle. Remember that the stars determine the length of the upper girdles. Stars too long result in short upper girdles with upper girdle angles too steep. Stars too short have the opposite effect, and the lower girdles are too long. The 48%-51% configuration is the best combination for us with regard to balance between stars and uppers and our ability to minimize leakage and maximize performance.

Im not sure if I want to touch anything in this thread with a 10 foot poll but I wanted to add a comment here.

The angle of the upper girdles is not only determined by the length of the stars but also there angle.
Lengthening the stars while keeping them at the same angle would result in steep girdle facets but it doesn''t have to be so.

One can not look at one set of data on one set of facets and jump to conclusions about another.

 

[strmrdr]

Date: 8/7/2005 9:38:35 PM
Author: JohnQuixote

Date: 8/5/2005 6:08:50 PM

Author: Rhino


Not true on both accounts bro. Hot spots are produced primarily by lengthening lower girdle facets not the presence of yaw. I would also note that when anal retentive clients *compare* H&A diamonds side by side in direct lighting ... guess which wins out 90% of the time? And this is before they even see or learn anything about a BrillianceScope! The visual balance is nothing short of spectacular in a precision cut stone with 80-82% lgs. Matter of fact I purposefully look for them.

Cool. Shifting gears here...Your statement about 80%-82% lower girdles winning out in direct lighting makes the further point about Brilliancescope very clear.



Lower girdle lengths and balance

Long LGF = >80% (narrow mains)


Why do cutters like to fashion long lower girdles? Weight retention and sales.


We know very well that in bright lights lower girdles >80% sell diamonds. When they are that long the pavilion mains are very NARROW, so they thin and intensify bright light, especially spotlighting like jewelry store halogens. The bright, direct lighting chamber of a Brilliancescope also rewards lower girdles >80% because of that narrow, intensified return. We think this is deceiving to consumers. As you clearly see in hearts patterning lower girdles >80% have notable splits in the Vs, reducing optimization, and creating LESS SURFACE AREA for the pavilion mains – which are the engines that drive light return. Sure, under halogen spotlights such narrow, intense return makes sales but the trade-off is less performance potential in other real-world lighting conditions.


So why don’t cutters shorten those lower girdles? It’s because the longer the lower girdles are the closer they are to the main pavilion angle, but the minute you shorten them you are polishing away more weight. It’s the age-old game of weight retention at the expense of performance.


There is nothing wrong with these diamonds. They are beautiful and there is demand among consumers for them. In head-to-head direct light they're winners, as stated.


Short LGF = b] (thick mains)


Many consider Eightstar diamonds to be among the most beautiful, yet they perform horribly on Brilliancescope. Why? The lower girdles are around 75% and don’t have the narrow, intense light return the Brilliancescope favors. No one of sound mind would argue the fact that Eightstar is one of the best performing diamonds in soft light like candlelight. Why? Very logical. It’s due to the 75% lower girdles (their approximate design for minors). Very thick pavilion mains with large surface area, so soft light is picked up and returned better.


It costs Eightstar more weight, but they have a notable footprint. Some people don’t like the way they perform in direct light as much as other diamonds. Again, logical.


In a blind test Eightstars may get ‘beat’ side by side in direct light (been there) but they typically ‘win’ in soft light with broadfire flashes you can see across a restaurant.


Balanced LGF = 77-80%


We strongly feel lower girdles in the 77-80% range represent the best balance. It costs a little more weight when cutting, but this minor facet axiom, coupled with no yaw for complete optimization of light return, provides performance rivaling the best diamonds head-to-head in direct light and soft lighting as well.


Almost all diamonds sparkle well in bright jewelry store lights. This is because the sheer volume of light returned to the eye overpowers fine-tuning of the cut such as we are discussing. In diffuse lighting and soft conditions like candlelight the minor facet particulars and how well the mirrors are focused and aligned with each other (patterning) becomes evident.



Of course taste varies for rounds. Some people like long LGF. Others like more rare, short LGF. Still others like 60% tables and some people don’t like rounds at all.


There are many combinations for beauty and we understand that, but in order to achieve balance we personally feel this is what you need:


Major proportions near Tolkowsky’s, with a slightly steeper crown to enhance dispersion and scintillation through contrast. True hearts patterning with absence of yaw that crisply aligns all mirrors in the pavilion for optimum light return. Crown patterning that logically follows the fundamentals of the all-important pavilion. Lower girdles in the range of 77-80% and stars from 48%-51% that empower blazing performance in direct light and robust performance in soft light. That is what we call Visual Balance™.


It is the best of all worlds in our minds.


Though well-known to cutters, this information rarely makes its way into the mainstream because simple weight retention and sell-ability drive the machine. In the same way that most consumers see far more 60/60 diamonds than ideals, they are more likely to see diamonds with long lower girdles, because they're more common in the mainstream.

I talked to John about this last night.
This post is way too much a defense of one way of thinking than a balanced look at the pro and cons of the various lgf lengths.
Also keep in mind that no one set of facets lives alone nor works alone.
It is possible to tune some of the other facets to overcome some of what selecting one set of parameters on another brings to the table while keeping the benifits of that selection.

 

[JohnQuixote]

Date: 8/8/2005 7:57:26 AM
Author: strmrdr

Date: 8/8/2005 3:26:29 AM
Author: JohnQuixote

Date: 8/7/2005 11:13:05 PM

Author: Midnight

Hi John,

I knew the ''Knight'' would be charging back

! You hinted that for perfect ''Visual Balance'' in WF''s opinion, the star facets should be around 48%-51%. Can you please elaborate on the pros and cons if it wasn''t within this range in terms of optical performance?

Charging back indeed. Nothing like being in giddy-up mode.

Our prescriptions for stars exist to eliminate leakage near the girdle. Remember that the stars determine the length of the upper girdles. Stars too long result in short upper girdles with upper girdle angles too steep. Stars too short have the opposite effect, and the lower girdles are too long. The 48%-51% configuration is the best combination for us with regard to balance between stars and uppers and our ability to minimize leakage and maximize performance.

Im not sure if I want to touch anything in this thread with a 10 foot poll but I wanted to add a comment here.

The angle of the upper girdles is not only determined by the length of the stars but also there angle.
Lengthening the stars while keeping them at the same angle would result in steep girdle facets but it doesn''t have to be so.

One can not look at one set of data on one set of facets and jump to conclusions about another.

Strm, Midnight was asking for our input. That is what I gave. I''ve clarified this as our own philosophy and approach.

Incidentally, if you want to keep crown angle (kites) constant the star angles will change along with upper girdles. It''s give and take since they meet. Here is what I meant when I said lower girdles will be steeper with longer stars (you can do this in your DiamCalc):

(6.00 mm diamond. Table 57.2, Depth 60.6, PA 40.8, CA 34.6, Girdle 1.0)

1. With stars at 46% (they will be 20.37 degrees) the upper girdles must be 40.69 degrees to meet and keep the overall CA at 34.6

2. If you lengthen stars to 56% (now 22.73 degrees) upper girdles must now be 42.23 degrees to keep the overall CA at 34.6.

No problem with these or other configurations, if you like them.