How significant are the star facets and lower girdles info?

[strmrdr]

Thats a nice presentation John and I think it serves more people than you think.
Now that you have explained what it is what is its effect and at what point does it become a quality issue rather than a technical issue?

I seem to remember someone telling me not to get too critical on h&a images or no one would ever get a diamond because they all have flaws if you look hard enough so whith this kind of stuff we need examples of the point where if its this good then shut up allready :}

 

[Regular Guy]

Storm,

Agreed. What do you say we hurry, and while he''s still asleep we TP his house!

Actually, I''m visualizing a scene from American Wedding II, on the dance floor; anyone see it? It does require a bit of follow up, though, to complete the picture.

As for me...after my boys turned my office into a studio for themselves, I''ve now got to find my IS again. Despite my innate curiosity about these things, and the understanding that the requirements for a buyer to not find a group of acceptable diamonds, but just one out of a pack that they will buy...probably mastering one tool at a time will be sufficient for my needs. Hopefully I will be able to learn the IS a bit at the gem show, without hassling anybody too much.

Many thanks.

 

[JohnQuixote]

Date: 8/5/2005 8:14:45 AM
Author: strmrdr
Thats a nice presentation John and I think it serves more people than you think.
Now that you have explained what it is what is its effect and at what point does it become a quality issue rather than a technical issue?

Thanks Strm.

I agree with you about service. That's the fundamental point I am trying to make. Those with expertise will work to safeguard consumers against things those consumers know nothing about.

Yaw is something Brian has been trying to communicate for years but it’s very advanced thinking, so instead of waiting for others to adopt a position he has acted by setting his own standards.

When does yaw become a quality issue? We are working carefully before making a presentation on observable influence. We do know it is a character issue within patterned diamonds.

Yaw influences angular path.

In an asymmetric diamond or one of low quality its presence does not make notable differences, since angles of light return are chaotic and unorganized in the first place.

In a symmetrically patterned diamond of the kind we favor the presence of yaw interrupts ordered angular spectrum. You can detect this somewhat with ASET but only in places where yaw causes returned light to cross the 75 or 45 degree color-borders in unintended places. In most cases it is only detectable in the pavilion view (H&A viewer).

So, is it a concern? Is it a big deal if light is returned at X degrees when, with no yaw, its angle within the pattern was supposed to have been X+10 degrees? Does it create groovy scintillation - or does it cause less unified performance and disrupt contrast? This overall performance question is larger than the static view reveals. As we learn more about dispersion & scintillation potential in each zone of the diamond we will be able to better gauge influence. Jim Caudill and AGS are working on a fundamental metric for dynamic contrast/dynamic fire that has great promise to handshake with an assessment of yaw’s influence.

Yaw alters Visual Balance™

As mentioned, severe yaw causes corrections that become obvious to measuring equipment due to azimuth shift (that level is picked up by Sarin/Ogi).

What we do know is that yaw that is not picked up by Sarin/Ogi can impact the character of a diamond’s beauty. Intentionally patterned minor proportions will not have their intended dynamic if yaw is present and alters the relationship they have with each other. Yaw can also influence pavilion mains’ interactions.

So, in patterned diamonds we know yaw influences character and we feel it can influence some aspects of performance.

 

[JohnQuixote]

Date: 8/5/2005 8:14:45 AM
Author: strmrdr

I seem to remember someone telling me not to get too critical on h&a images or no one would ever get a diamond because they all have flaws if you look hard enough so whith this kind of stuff we need examples of the point where if its this good then shut up allready :}

LOL. It's all about levels of comfort, Strm. For your purposes we can talk 3D scans relative to actual images relative to Okuda scopes relative what you observed in a dark room with a candle and a white cat providing illumination. The cautionary tale here is to allow consumers to seek the learning curve they are comfortable with.

As for when to ‘shut up already’...

Let the consumer decide.

For those interested, Brian has been talking about hearts patterning - “It’s all in the hearts” - for many years.

In 2004 he described yaw to other leading minds at the Moscow cut summit. But unless you are a cutter who has physically sat at the wheel and learned ninja tactics of digging, painting, cheating and getting a facet to run it’s hard to understand (cutters are tricky, tricky). Paul Slegers was the first pro outside of WF to see what Brian was saying about yaw and measuring devices. Bruce Harding is a colored gemstone cutter and ‘got it’ once the dynamic duo approached him.

Years before (way back in pre-Pricescope days) Brian offered information about the importance of hearts patterning, which is ALL about minor facet relationships and optimizing light return. Some didn’t pay attention. Brian has always advocated LGF less than 80% for preferred performance. Others cut diamonds with LGF >80% because they perform well in certain mechanical assessments. Since that time studies show that >80% some aspects of performance decline, reinforcing Brian’s position on best visual balance™.

Fast-forward to 2005... The info and measures AGS and GIA are now bringing out are a testament to the importance of pavilion patterning Brian never 'shut up' about. HRD has a new laser machine for diamond processing measuring on 3 axes, so it likely detects yaw. Still, the market-at-large may never care about this. The niche patterning we are discussing happens in less than one in a million diamonds (though that may be on the rise thanks to the spread of good cut info). Helium may pick up all yaw and that will be a stride forward for us, but until we have a concrete metric to assess each diamond zone’s potential through a range of motion we won’t have all of the answers about overall influence.

The labs have no plans for grading H&A patterning - it’s not a big enough part of the market. At the IDCC in Moscow Brian didn't 'shut up' - he presented a grading system for H&A. It was hoped that laboratories and peers would unite to maintain higher standards for manufacture of H&A 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 safeguard consumers. It guarantees no yaw, along with the most visually balanced minor facet combinations, among many others things.

...This all goes to support the fundamental point I am trying to make: Those with expertise and integrity will work to safeguard consumers against things those consumers know nothing about. We have the info for those who want it and ‘shut up already’ for those who don’t.

In our experience some customers (yes, I am thinking of several of you) are data-hungry. I yahoo and phone with you, send hearts images out and discuss angles and patterning until the sun goes down. Frankly I love it. Other customers call in because they saw an ACA on a friend’s hand. It was all sparkly and they want one - 'now where do I send the wire?' No matter how much information goes out, the same guarantees apply.

 

[JohnQuixote]

Date: 8/5/2005 9:28:08 AM
Author: Regular Guy
Storm,

Agreed. What do you say we hurry, and while he''s still asleep we TP his house!

Actually, I''m visualizing a scene from American Wedding II, on the dance floor; anyone see it? It does require a bit of follow up, though, to complete the picture.

As for me...after my boys turned my office into a studio for themselves, I''ve now got to find my IS again. Despite my innate curiosity about these things, and the understanding that the requirements for a buyer to not find a group of acceptable diamonds, but just one out of a pack that they will buy...probably mastering one tool at a time will be sufficient for my needs. Hopefully I will be able to learn the IS a bit at the gem show, without hassling anybody too much.

Many thanks.

TP? Say now, what did I do to deserve that?

I''m not knocking your new DiamCalc fun. I''m just saying there are pieces of the puzzle that are more simple to acquire with diamond in-hand - and more telling.

Are you only going to have handheld IS at the show? Unless you can examine dozens of diamonds with patterning at and near the levels we''re talking about in standardized conditions with H&A viewer, correlated with IS (and now ASET) you won''t be getting the flavor, Ira. If you were to make this an empirical study you''d also need to know the proportions - and since error is possible you really need redundancy among the candidates.

 

[Rhino]

Ok... lots of things to address here but lets take em one at a time.

Firstly, I mentioned ways in which we observe facet yaw. This graphic demonstrates your words to the "T" John when you state...

"Yaw alters Visual Balance" and "Yaw influences angular path".

There are 2 areas under the table where this can be observed as pointed out in the graphic below.

The presence of yaw disrupts the optical design of the diamond. The more yaw that is present the more the design is altered and the weaker the light is that is transmitted through the table facet. LightScope technology allows us to both see and photograph this phenomena whereas every other red reflector we''ve attempted to photograph this with has been unsuccessful.

Next is an example of a stone with none to very little yaw.

 

[Rhino]

To the general public reading this ...

John and I are splitting MAJOR HAIRS here. Most H&A diamonds DO have yaw to some degree. In some H&A diamonds it is more notable than others but just keep in mind that *EACH* of the stones in this example are both honies. It is a factor we definitely consider and we do disregard stones where yaw impacts the face up appearance but if it is minor and does not impact face up appearance its no reason to reject a stone.

Ok... the graphic below is showing another H&A diamond with little to no yaw next to the example above except both are scaled down for the screen.

You can see the differences between the 2 and the perfection of the optical design of the stone on the left.

 

[Rhino]

woops... here''s the graphic.

 

[Rhino]

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

While I am a nut for details ... here are the hearts for the stone on the right. Nothing obvious to me there. I agree severe yaw would disrupt the hearts, but not at the level I''m observing. Are we on the same page?

 

[strmrdr]

Date: 8/5/2005 5:14:44 PM
Author: Rhino
To the general public reading this ...


John and I are splitting MAJOR HAIRS here. Most H&A diamonds DO have yaw to some degree. In some H&A diamonds it is more notable than others but just keep in mind that *EACH* of the stones in this example are both honies. It is a factor we definitely consider and we do disregard stones where yaw impacts the face up appearance but if it is minor and does not impact face up appearance its no reason to reject a stone.

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

 

[strmrdr]

Date: 8/5/2005 5:15:45 PM
Author: Rhino
woops... here''s the graphic.

Iv noticed that difference in some stones LS images in that area but never got around to asking about it.
It often shows up more in stones with looser physical symmetry that still score well in optical symmetry so figured it was just part of that.

 

[Regular Guy]

Pssst Storm, we''re too late, I think he''s up.

Sorry John, only good fun meant. Actually, I think the dance off is just starting.

Re:

Date: 8/5/2005 4:28:04 PM
Author: JohnQuixote

Date: 8/5/2005 9:28:08 AM
Author: Regular Guy

Are you only going to have handheld IS at the show? Unless you can examine dozens of diamonds with patterning at and near the levels we''re talking about in standardized conditions with H&A viewer, correlated with IS (and now ASET) you won''t be getting the flavor, Ira. If you were to make this an empirical study you''d also need to know the proportions - and since error is possible you really need redundancy among the candidates.

I think at this point, without attempting to hide my practical ignorance of these things...I am trying to get a handle on the lowest hanging fruit. From that point of view, understand I''m not going to either Tiffany''s, GOG, or WF...I''m going to a Gem show. For fun. Kind of like not sorting between 18K vs 24 K gold, but sifting with a pan out in a gold mine, no? So, I''m trying to be environmentally appropriate. John, you talk about a funneling process, where it makes sense to sift beginning with HCA (and that''s how it''s intended to be used, right). Likewise, really not having used the IS, per se...don''t you think that''s the place to start. Isn''t the protocol...having determined a set of options that tend to not leak light, then to discern between them, how precise the patterning is? Then, from past posts here, I think ASET viewing will take some additional study. I''m taking it slow.

OK, sorry to interrupt.

 

[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?

 

[Midnight]

John,

Thank you for the excellent tutorial...yes, I was still up at 3:00am reading all your hard work!

Let''s see if I''ve learned anything. I would guess the LGF on Rhino''s examples are around 80%?

Rhino,

You might already be working on a response to this. Can you please post the BS scope on your two examples. It would be interesting to see if the BSscope rewards yaw and LGF >80%.

 

[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.

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

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.

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.

Sarin/Ogi

This is not correct. Sarin and Ogi do not detect yaw. Sarin measures angles. OGI, because of patents, establishes points and then deducts angles. In both cases the machines work from point to point seeing flat facets in 2D shadow of the diamond. If the rotation of the machine table doesn''t match the azimuth of the facet (as it does not with yaw - see diagram below) the slope indications are incorrect.

I never said Sarin or OGI detect yaw. There is nothing on their reports that indicate its presence or absence of it. I clarified what I meant in my prior post. I think we''re on the same page regarding these devices and yaw?

Helium

Brian was one of the only Americans at the IDCC in Moscow, and had the privilege of an introduction to Helium''s fundamentals. Very impressive! Garry has also described the system to me and it uses different axes than Sarin/Ogi. We are hopeful it measures yaw and waiting for evidence. Jon, any info you can add would be welcome.

Once it''s here and I have the chance to sit and play with it for a while I''ll be happy to contribute. Expecting it next week.

Also, Jon, before you complete your web page about this you may want to consult with Brian, who is the identifier of yaw. We have dedicated considerable research along with Bruce Harding who, self-admittedly, had his CAD skills pushed to the max on this project. Peer review is always a good thing, friend.

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,

 

[Rhino]

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

Date: 8/5/2005 5:14:44 PM
Author: Rhino
To the general public reading this ...


John and I are splitting MAJOR HAIRS here. Most H&A diamonds DO have yaw to some degree. In some H&A diamonds it is more notable than others but just keep in mind that *EACH* of the stones in this example are both honies. It is a factor we definitely consider and we do disregard stones where yaw impacts the face up appearance but if it is minor and does not impact face up appearance its no reason to reject a stone.

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

Good question strm. I will not know the answer to this until Helium arrives.

 

[Rhino]

Date: 8/5/2005 6:04:17 PM
Author: Midnight
John,

Thank you for the excellent tutorial...yes, I was still up at 3:00am reading all your hard work!

Let''s see if I''ve learned anything. I would guess the LGF on Rhino''s examples are around 80%?

Rhino,

You might already be working on a response to this. Can you please post the BS scope on your two examples. It would be interesting to see if the BSscope rewards yaw and LGF >80%.

Before I do Midnight I want to pose a question to strm (gotta test him You''re welcome to give an educated guess to but here''s my question.

When correllating BrillianceScope results with reflector technology (particularly LightScope) and the diamond exhibits pale reds as opposed to dark reds which metric generally takes the hit?

a. white light return
b. colored light return
c. scintillation

Only until I get a couple of responses (especially strms) then I''ll show you B''scope results.

hehe

Peace,

 

[strmrdr]

Date: 8/5/2005 8:29:48 PM
Author: Rhino

Date: 8/5/2005 6:04:17 PM

Author: Midnight

John,


Thank you for the excellent tutorial...yes, I was still up at 3:00am reading all your hard work!

Let''s see if I''ve learned anything. I would guess the LGF on Rhino''s examples are around 80%?


Rhino,


You might already be working on a response to this. Can you please post the BS scope on your two examples. It would be interesting to see if the BSscope rewards yaw and LGF >80%.

Before I do Midnight I want to pose a question to strm (gotta test him You''re welcome to give an educated guess to but here''s my question.


When correllating BrillianceScope results with reflector technology (particularly LightScope) and the diamond exhibits pale reds as opposed to dark reds which metric generally takes the hit?


a. white light return

b. colored light return

c. scintillation


Only until I get a couple of responses (especially strms) then I''ll show you B''scope results.

hehe


Peace,

lol ill let some other people answer first.
Ask me something a little tougher next time :}

 

[Midnight]

Date: 8/5/2005 8:29:48 PM
Author: Rhino

Date: 8/5/2005 6:04:17 PM
Author: Midnight
John,

Thank you for the excellent tutorial...yes, I was still up at 3:00am reading all your hard work!

Let''s see if I''ve learned anything. I would guess the LGF on Rhino''s examples are around 80%?

Rhino,

You might already be working on a response to this. Can you please post the BS scope on your two examples. It would be interesting to see if the BSscope rewards yaw and LGF >80%.

Before I do Midnight I want to pose a question to strm (gotta test him You''re welcome to give an educated guess to but here''s my question.

When correllating BrillianceScope results with reflector technology (particularly LightScope) and the diamond exhibits pale reds as opposed to dark reds which metric generally takes the hit?

a. white light return
b. colored light return
c. scintillation

Only until I get a couple of responses (especially strms) then I''ll show you B''scope results.

hehe

Peace,

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.

 

[RockDoc]

Date: 8/5/2005 6:10:10 PM
Author: Rhino

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

Date: 8/5/2005 5:14:44 PM
Author: Rhino
To the general public reading this ...


John and I are splitting MAJOR HAIRS here. Most H&A diamonds DO have yaw to some degree. In some H&A diamonds it is more notable than others but just keep in mind that *EACH* of the stones in this example are both honies. It is a factor we definitely consider and we do disregard stones where yaw impacts the face up appearance but if it is minor and does not impact face up appearance its no reason to reject a stone.

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

Good question strm. I will not know the answer to this until Helium arrives.

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

 

[strmrdr]

Date: 8/5/2005 8:29:48 PM
Author: Rhino

Date: 8/5/2005 6:04:17 PM

Author: Midnight

John,


Thank you for the excellent tutorial...yes, I was still up at 3:00am reading all your hard work!

Let''s see if I''ve learned anything. I would guess the LGF on Rhino''s examples are around 80%?


Rhino,


You might already be working on a response to this. Can you please post the BS scope on your two examples. It would be interesting to see if the BSscope rewards yaw and LGF >80%.

Before I do Midnight I want to pose a question to strm (gotta test him You''re welcome to give an educated guess to but here''s my question.


When correllating BrillianceScope results with reflector technology (particularly LightScope) and the diamond exhibits pale reds as opposed to dark reds which metric generally takes the hit?


a. white light return

b. colored light return

c. scintillation


Only until I get a couple of responses (especially strms) then I''ll show you B''scope results.

hehe


Peace,

My answer is it depends.
1> in what area the pink is.
2> the extent of it.
3> what type of light return the stone is tuned for.

It indicates less light return but the color doesnt tell you how that missing light return would have been returned.

That said its: White light that often takes the big hit.

 

[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.

Peace,

 

[Rhino]

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

Date: 8/5/2005 6:10:10 PM
Author: Rhino

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

Date: 8/5/2005 5:14:44 PM
Author: Rhino
To the general public reading this ...


John and I are splitting MAJOR HAIRS here. Most H&A diamonds DO have yaw to some degree. In some H&A diamonds it is more notable than others but just keep in mind that *EACH* of the stones in this example are both honies. It is a factor we definitely consider and we do disregard stones where yaw impacts the face up appearance but if it is minor and does not impact face up appearance its no reason to reject a stone.

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

Good question strm. I will not know the answer to this until Helium arrives.

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

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.

This picture here I have saved on my harddrive (below) as it is perhaps the most perfectly cut stone I have ever seen in my life. I almost wish I didn''t sell it.

btw ... these hair splitting features are what differentiates between the best and worst in some brands I''ve had the chance to analyze. Even some which have solid IS images.

 

[strmrdr]

Rhino,
I remember that diamond, pure perfection.
Yummy.
As I recall 0 degree variation in the pavilion and .1 degree in the crown facets with the minors as tight too.

 

[Dancing Fire]

Rhino
that is one heck of a stone

all the hot spots are the same (small size) all the way around the arrow shafts,that tells me this stone has no yaw.all the harts on this stone should look identical.

 

[diamondsrock]

I would have loved to see that stone under various lighting conditions. I''ll bet it was a show stopper!

 

[JohnQuixote]

EDITED:

Otay.

The posts since my last entries here were a lot to read. My first reaction was “OH NO, BAD INFO! Aieee!”

After reading again I think Jonathan is simply not on the same page here with what he thinks yaw is, and is running forward with his impression (which I believe to be azimuth shift).

I know quite well you would not try to give bad info, Jon, so I apologize if any of my replies are reactionary. As with any new concept there needs to be open discussion to empower understanding, which I hope will continue.

Facet yaw was not detectable before reflectors. Brian Gavin identified the phenomenon and gave it the name. It is indigenous to cutters. With the exception of Paul Slegers and Bruce Harding, no one has grasped the cause without elaborate explanation (and we are talking about a few of the best minds in the trade).

I will try a reset of the description: When graining forces the cutter to run the facet from ‘east to west’ rather than ‘north to south’ the extra time that one side of the facet spends on the wheel, coupled with the polishing strategy used to straighten the girdle, leaves a palpable tilt in a 3rd dimension apart from conventional azimuth shift on the main.





I’m sorry guys, you need to ignore everything Rhino posted. Those are erroneous views of facet yaw and how to interpret it.

I’m very sorry Rhino. You need to go back to square 1 with yaw. I recall we had a discussion after JCK about this on the phone. I guess I didn’t understand your misunderstandings. You’ve gone to some trouble to work this out in your mind but you’ve missed the most important point.

Facet yaw occurs in the pavilion MAINS. That’s why the concern. If there’s no yaw in the mains the cutter isn’t forced to disguise it. When it does occur in the mains the only way to cover it up is to paint or dig the lower girdle halves (please go see Brian & Bruce’s diagram on page 1). These polishing techniques straighten out the girdle and hide pavilion yaw from the machines, but that primary yaw is still there.

You can’t see primary yaw from a crown view due to simple obscuration. Some ancillary yaw may show up in lower girdles - depending on how they were polished in order to straighten up primary yaw - but you really can’t judge this in the crown because there is too much else going on, and it doesn’t address the main issue anyway.

Please go back to page 1 and review the hearts views I posted where yaw is identified. This is the ONLY way to assess yaw.

Remember that a single heart is a joining of reflections from 2 adjacent main pavilion facets. Each main pavilion facet reflects on the opposite side and the lower girdle half separates the arrowhead above the heart. Yaw cannot be seen in the crown view, since the mains appear as arrows and are obscured.

 

[JohnQuixote]

Date: 8/5/2005 5:10:24 PM
Author: Rhino
Ok... lots of things to address here but lets take em one at a time.

Firstly, I mentioned ways in which we observe facet yaw. This graphic demonstrates your words to the ''T'' John when you state...

''Yaw alters Visual Balance'' and ''Yaw influences angular path''.

There are 2 areas under the table where this can be observed as pointed out in the graphic below.

The presence of yaw disrupts the optical design of the diamond. The more yaw that is present the more the design is altered and the weaker the light is that is transmitted through the table facet. LightScope technology allows us to both see and photograph this phenomena whereas every other red reflector we''ve attempted to photograph this with has been unsuccessful.

Sorry again, friend. You don’t understand. Lightscope is unsuccessful for the same simple reasons other Gilbertson-based reflectors are.

FIRST: As mentioned, you can’t see it in the crown view, as the arrows camouflage what’s going on. The mains are dark due to obscuration and you can’t detect anything in them.

SECOND: What you think you’re seeing under the table could be any number of things. The simplest cause could be leveling of the diamond. It could be angle variance. It could be the diamond out of round or simple azimuth shift. To confuse the issue, the stars and the table itself reflect in the center of the image while the lower girdle divisions have multiple reflections. It is a jambalaya of different elements that are subject to tertiary reflections and distortions.

As for your reflector colors, slight hue changes within those double reflections could be due to tilt, the diamond out of round, patterning variation, angle variance or even a fingerprint on the light source. They may have nothing to do with azimuth shift and if they do there is no way to tell if they are some sort of ancillary yaw without first looking for primary yaw in the pavilion mains which is very simple to do with the H&A viewer.

So even assuming you have a 100% perfectly level diamond, these things still have multiple causes and multiple reflections. The thing we do know is that it’s not yaw.

 

[JohnQuixote]

As a simple example of complexity, here is a perfectly patterned diamond that is simply out of round. Look at the sudden changes due to multiplicity and distortion.

Left = 6.60x6.60x4.00 Right = 6.60x6.50x4.00 (both are still traditional AGS0s)

…And remember that this is a diamond with otherwise perfect computer numbers. See how everything under the table changes? I could replicate others with tilt, angle variance, non-perfect patterning, azimuth shift for even greater distortion...

The point is that there is too much potential for disruption in the crown view to assess pavilion construction closely enough.

 

[JohnQuixote]

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

While I am a nut for details ... here are the hearts for the stone on the right. Nothing obvious to me there. I agree severe yaw would disrupt the hearts, but not at the level I'm observing. Are we on the same page?

Yes, we’re more on the same page with the H&A image, since you can see yaw in this view.

Slight yaw of lower girdles appears in 3 places (1:00, 5:00, 9:00). I’ll try to say this only a few more times, but you cannot see yaw in the crown view so these do not correlate with any reflections that you believed to be yaw in the corresponding lightscope illustrations above. What you pointed out previously has nothing to do with main pavilions, as this does.