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How significant are the star facets and lower girdles info?

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Date: 8/23/2005 3:48:47 PM
Author: Paul-Antwerp
Yawn,

I think that I deserve a medal for reading through all this, and remaining attentive. It probably is because I still understand what each person is saying, and the fact that I just returned from a true holiday is also helpful.

Anyway, what I see here is a classical example of people defending their opinion, without really understanding what the other person is defending.

In this, being a cutter and knowing what happens at the wheel, I fully understand what Brian and John are trying to explain. When we last met in Vegas, we agreed that we do not know yet to which extent the presence of facet yaw is detrimental to the performance of a round brilliant, but since it makes the light path less predictable, it is bound to have a negative effect. We explained it together to Jim Caudill of AGS, and I hope that he is now a motor behind figuring out the extent of that negative effect.

On the other hand, I see my dear friend Jonathan defending a point of view, based upon what he observes. Now, we can all agree that Jonathan is probably the world's best observer of diamonds and the best criticist, but I hate to say that the best criticists are not able to produce a good movie. At this point in time, I still do not understand what Jonathan thinks he is observing when he describes yaw, but I am sure that it is something completely different from what Brian and I know to be yaw.

Correct me if I am wrong, but I think that part of the problem is due to a simplification in the courses on light behaviour in gemmolical courses. I learned what a ray of light (which is uni-dimensional) does when it hits a facet. Now, this facet is taken as a line (being uni-dimensional), while in reality, a facet is a plane, thus two-dimensional. The whole theory of light behaviour (whether a ray of light is reflected or bent) is explained in that uni-dimensional way. Now, a facet being two-dimensional, there is an infinite (nice word) number of angles on that plane. The simplification is necessary to understand what is happening with light in a gem, but everybody seems to have forgotten that there has been a simplification.

Enough for now, I did not want to stir up the commotion again. Just remember, when you were about 2, your parents told you that anyone older than 18 was a grown-up. Being your current age, do you not consider that this is not entirely the case. Does this mean that our parents lied to us? No, but we should not continue to follow their simplifications.

Live long,
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Thank you Paul. I'll look for an appropriate medal. Meanwhile, here's your star
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and it's good to have you back
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Your observations are appreciated. It's the reason this issue has been left alone for now. I do hope to put up graphics illustrating this in terms that make it more clear, but as you noted the issue is multi-dimensional. Your movie critic analogy is a good one. In any event, the thread is already cumbersome and Brian has counseled me to avoid further redundancy. Rhino, thanks for your patience. I hope to get back to this in the next few days.

We have maintained commuications with Jim on this, but they are very busy with ASET and the new grading system. He acknowledges the studies and has confirmed our opinion that the machines don't pick up what we are describing, just as with indented naturals.
 
Date: 8/17/2005 8:33:08 PM
Author: Dancing Fire
yes...would love to see some ACA hearts.
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DF - Somehow I missed this. Thanks for the request (as well as Belle and Strm). You all make logical appeals. I will move this to the front burner.
 
Hey Paul,

Good to see you back and also for your interest in this topic. As of Friday last week I have conducted new research that confirms beyond a shadow of a doubt exactly what I''ve been saying. There isn''t anything I disagree with regarding Brians research on this subject and it appears we are very much on the same page.

The one area of disagreement is that Brian and John believe for some reason that what I am observing and photographing IS NOT the results of azimuth deviation or yaw but are the results of a tilted diamond etc. So they are claiming that my observation and declaration are based on a faulty foundation. Anything but what I am saying I am actually claiming to observe. Our latest research confirms that I am observing and photographing exactly what I thought EXCEPT I would make one point of note. We are able to now photograph and measure facet deviation from ideal even before it begins to alter a heart. This is a first in the world of gemology! :) Can I have a star too John?!?
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As I collect more graphics and data I planned on publishing it in this thread for demonstration and will do so as time allows.

Once again ... good to see you back Paul.

Warm regards,
 
Date: 8/15/2005 4:19:37 AM
Author: Garry H (Cut Nut)
Rhino here is an exercise:

1. Model a diamcalc stone with the average angles of your stone above.
2. Save it as a DXF file under Cut > Export >AutoDesk DXF (see this thread post 22 for help https://www.pricescope.com/community/threads/user-tips-for-diamcalc.32366/ )
3. Open the stone model you saved in the same way Cut> Import> AutoDesk DXF
4. now open the advanced tab on the lower right
5. open a new DiamCalc and open the stone above
6. open its advanced tab on the lower right also
7. Then compare the deviations in each facet for azimuth and slope (facet angle)

Brian, as we discussed this in Vegas, any flat facet can be described as a plane in a virual space by two (only two) angles. Azimuth and slope are enough. What you are describing is a bit of azimuth and a bit of slope change.
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I just played with DiamCalc to "yaw" one pavilion main.

I took Tolkowsky proportions, 56% table, 79% Lower Girdle facets and then changed azimuth and slope of one pavilion main (3 o'clock) on 2° and 0.5° correspondingly. Then I adjusted two neighboring lower girdle facets to keep the meet points.

Cut nerds can download and play further with the resulting GemAdviser file

yaw_05ang_20az_56_tolk.gif
 
An Elephant Stamp and a Gold Star for Leonid.
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This is the effect of a Yawed facet that has been polished obliquely across the facet.

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After reading the previous pages (and being slightly to mostly lost for most of it), I have a question. If I understand yaw correctly, it would be to place a diamond table side down, looking at an exactly straight-on angle, rather than seeing a flat plane, I would see a surface (of the facet or main) that twisted away from me either to the right or to the left when it shouldn''t twist at all? Or have I oversimplified things a bit and completely missed the boat?

Shay
 
Sorry, one more question. Would this explain a B-scope that had a great result on the graph; and yet looking at the light views, there would be an obvious out of balance to the light return. (one side of the diamond lit up and the other dark or some variation thereof) EXPERTS: Am I getting it, or missing the boat?

Shay
 
Okay,

I am NOT a rocket scientist, you all know that. I also know this. You can have a Sarin measurement and a Diamcalc image yet when you take a picture through the camera or the idealscope or the firescope or the Aset tool what you get will not necessarily match the predicted image of the diamcalc as taken from the Sarin measurements.

Perhaps this is no longer true, but it was once, and I suspect that it still is. I will leave to those who are gemology''s version of rocket scientists to figure this out completely, but I suspect that calculated images will NEVER show us the actual image that we are going to see when we inspect the diamond in real life.

I have a lot of respect for the parties involved in this discussion, but Rhino, I also question if your research based on calculated images will match what will actually appear in the stone. I think there will need to be some very expensive research done if we are to know this for sure...

Wink
 
Wink it all gets down to the scan accuracy.

Because Sarin and Ogi want quick and dirty results (because that''s what their customer bas wants), the scans can often not pick up Gavin''s Yaw.

But most of this inability comes form inaccurate Azimuth measurement.

Now Rhino has his Helium, he will be able to measure Yaw :)
 
Date: 8/26/2005 4:04:11 PM
Author: Wink
Okay,


I am NOT a rocket scientist, you all know that. I also know this. You can have a Sarin measurement and a Diamcalc image yet when you take a picture through the camera or the idealscope or the firescope or the Aset tool what you get will not necessarily match the predicted image of the diamcalc as taken from the Sarin measurements.


Perhaps this is no longer true, but it was once, and I suspect that it still is. I will leave to those who are gemology''s version of rocket scientists to figure this out completely, but I suspect that calculated images will NEVER show us the actual image that we are going to see when we inspect the diamond in real life.


I have a lot of respect for the parties involved in this discussion, but Rhino, I also question if your research based on calculated images will match what will actually appear in the stone. I think there will need to be some very expensive research done if we are to know this for sure...


Wink
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Howdy wink :}
Ill tackle a couple of your questions because i asked simular ones:
Lightscope is Rhino''s version of a red reflector scope like the I.S. it isnt generated. I find that it shows better details than the typical IS setup having compared images from the same diamond in both.

Your right the current sarin isnt accurate enough for this kind of work.
The helium scanner is and the models Iv seen based on its scans are great and very very very close to the real thing.
Stay tuned for some exiting stuff when Brian gets his in and Jon starts talking about some of the stuff he is working on.
There is going to be a ton of new stuff coming up as the new tech is starting to get used.
I can see but wont predict that what we know about the effects of diamond cut will double in the next couple years.
 
Date: 8/26/2005 4:41:35 PM
Author: Garry H (Cut Nut)
Wink it all gets down to the scan accuracy.

Because Sarin and Ogi want quick and dirty results (because that's what their customer bas wants), the scans can often not pick up Gavin's Yaw.

But most of this inability comes form inaccurate Azimuth measurement.

Now Rhino has his Helium, he will be able to measure Yaw :)
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Garry, we think Helium is fabulous - congrats to the MSU guys (and you too) on its development. You all have been working a long time to bring it to us.
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However I think the question about showing yaw is not the accuracy of the measurements so much as the number of places being measured and the exact points of those measurements.

Does helium show indented naturals? Curious.
 
In my next life I want to be born with a math computer chip in my brain and enough money to buy all the new toys!
 
Hello gentlemen and ladies.

Ok what are we going to do with these guys Paul? Poor John is driving me mad asking me to help them. Leonid my dear friend you been led down the primrose path of azimuth shift. Guys this is not a great gemological discovery. We have known of it for many years.

DiamCalc is so powerful that you can arrive at conclusions that are impractical. The great flexibility allows you break rules of how cutting works so layman operators may do things you would not do in the real world. In this case I fear you must leave it up to those who work with rough to communicate the subject.

You can post page after page after page of graphs and numbers until we are bludgeoned with them but it will only obscure the issue and convolute the thread unless you understand the premise. Right now you are showing a symptom that is already visible, even to the machines. Helium will help show us very, very accurate azimuth shift. But if it is not making all the measurements necessary it cannot show us yaw or indented naturals. Actual diamonds are not simple wire frames or a collection of edges and points describing an assumed outline. Sarin and Ogi have been great, and Helium will now give us better accuracy. We give praise and credit to these innovations.

Unless you polish rough you simply may not understand yet. This has been said first by John, then myself and now Paul. Good students of cut listen to what cutters have to say so class please listen.
 
What is Yaw?

YAW is the RESULTANT EFFECT of azimuth shift, when the facet has been polished in an East to West or West to East direction.

Edge detection machines we are aware of do not take enough measurements to "see" facet yaw. Remember these devices measure only certain points and assume straight lines. When polishing a real life diamond there are deviations possible in places that the current machines do not measure: Their edge detection merely assumes a certain line is there thus the inability to see indented naturals and yaw.

Scanning machines would have to measure the slope at the following intervals (depicted by the orange lines) and calculate the difference in slope on that particular facet in the same manner as it calculates azimuth shift from its designated indexed position.

Diffof-yaw2.jpg
 
Let us understand that C is what the machines are measuring for slope. However they would have to measure the slope at just inside points A and B (not merely points A and B) as well as at C order to calculate the difference in slope at all of these – (1) Point A to B (2) Point A to C (3) Point C to B.

These additional slope measurements would be necessary in order to evaluate the amount of yaw caused by the azimuth shift – and by the way things were adjusted by the cutter. Remember, he did what he could to straighten things out which has disguised but not omitted the yaw.

Now if possible this would be easier on large facets but much more difficult on smaller surfaces.

Diffof-yaw3.jpg
 
I am going to have some fun with my friend Leonid, for whom I have the greatest respect. He has learned more than most will ever know about diamonds. He also has helped many thousands of consumers make better decisions about diamonds. He may be among the most significant contributors to improvement of consumer knowledge.

But for today I am a diamond cutter and Leonid is my young apprentice.
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I downloaded the gem file that Leonid made available online and examined his handiwork.

Hello Leonid. Oh no, Leonid. This is not Yaw. Let me explain. But first Garry is right. We need an Elephant stamp to stamp out what you have done!

Leonid I am sorry, I may have to dismiss you as my diamond cutter. There is no place for you in our factory. We can all just adjust slope and azimuth with a click of a button but then you have to clean up the mess and make sure meet point symmetry is passable for Ideal 000 or EX EX.

You failed to show the whole story, so let me tell it again. See? The crown is twisted to the pavilion - it would not pass in our factory.

BadCutter.jpg
 
Naughty Garry. Do you see what you did to poor Leonid?
Guys, diamond is expensive. Please handle with care.

Ok the master will fix it now. Azimuth shift remains on the main pavilion you changed. Adjustments are necessary to make sure all meet points allow us to have great meet point symmetry and no twist between the crown and pavilion.

Look what I did. I still retained the weight on your 2.00ct. What a cutter, what a Genius!
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PrimoCutter.jpg
 
Now here is the result. It is impossible to have perfect optical symmetry but the meet points are great. Just remember that in these pictures all other facets are perfect in terms of indexing because of the computed simulation in DiamCalc. This does not happen in real life.

Off the topic, this meet point symmetry is an excellent example of showing a stone with EX or Ideal meet point symmetry that would not have optical symmetry.

I can provide my gem file for anyone to see what was done here. I receive $350 per hour to tutor cutters, but today you can have this file for the price of listening to what is practical rather than theoretical.
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Paul, no sneaking these changes to them please. John you get the file for free.

So some things you do with your wire frames would never be done on an actual diamond. In tricky instances like this you need someone who works with rough to show you. Remember in computer basketball games you can throw a great swish backwards from full court away but real life it is more complicated than that, even for the pros.

More to come.

FIXNOTyaw_05ang_20az_56_tol.jpg
 
Date: 8/26/2005 4:04:11 PM
Author: Wink
Okay,

I am NOT a rocket scientist, you all know that. I also know this. You can have a Sarin measurement and a Diamcalc image yet when you take a picture through the camera or the idealscope or the firescope or the Aset tool what you get will not necessarily match the predicted image of the diamcalc as taken from the Sarin measurements.

Perhaps this is no longer true, but it was once, and I suspect that it still is. I will leave to those who are gemology's version of rocket scientists to figure this out completely, but I suspect that calculated images will NEVER show us the actual image that we are going to see when we inspect the diamond in real life.

I have a lot of respect for the parties involved in this discussion, but Rhino, I also question if your research based on calculated images will match what will actually appear in the stone. I think there will need to be some very expensive research done if we are to know this for sure...

Wink
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Wink, you should give yourself more credit. There are still things that only the actual diamond can tell us. You can have the gem file for free too.
 
Date: 8/26/2005 8:31:24 PM
Author: BrianTheCutter

Date: 8/26/2005 4:04:11 PM
Author: Wink
Okay,

I am NOT a rocket scientist, you all know that. I also know this. You can have a Sarin measurement and a Diamcalc image yet when you take a picture through the camera or the idealscope or the firescope or the Aset tool what you get will not necessarily match the predicted image of the diamcalc as taken from the Sarin measurements.

Perhaps this is no longer true, but it was once, and I suspect that it still is. I will leave to those who are gemology''s version of rocket scientists to figure this out completely, but I suspect that calculated images will NEVER show us the actual image that we are going to see when we inspect the diamond in real life.

I have a lot of respect for the parties involved in this discussion, but Rhino, I also question if your research based on calculated images will match what will actually appear in the stone. I think there will need to be some very expensive research done if we are to know this for sure...

Wink
Click to expand...
Wink, you should give yourself more credit. There are still things that only the actual diamond can tell us. You can have the gem file for free too.
Click to expand...

Thank you sir,

Now if I only had a clue what to do with it...
 
since i did not receive brian''s masterwork gem file for free, i thought i''d try and fix leonid''s diamond.......
please do not throw me out the window!

mytry1.jpg
 
the rest of the story...

mytry_2.jpg
 
Date: 8/25/2005 4:50:28 PM
Author: Shay37

After reading the previous pages (and being slightly to mostly lost for most of it), I have a question. If I understand yaw correctly, it would be to place a diamond table side down, looking at an exactly straight-on angle, rather than seeing a flat plane, I would see a surface (of the facet or main) that twisted away from me either to the right or to the left when it shouldn't twist at all? Or have I oversimplified things a bit and completely missed the boat?

...

Sorry, one more question. Would this explain a B-scope that had a great result on the graph; and yet looking at the light views, there would be an obvious out of balance to the light return. (one side of the diamond lit up and the other dark or some variation thereof) EXPERTS: Am I getting it, or missing the boat?

Shay
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Hi Shay - thanks for reading through all of this.

You have not oversimplified (that is the gist) but you have magnified. These can be differences of mere microns. If you have looked at the photos and graphics of azimuth shift you can see that yes, the presence of yaw can be indicated by the appearance of some 'twist' as you describe. In asymmetrical diamonds it should not matter as much as it does in a diamond such as a H&A where exact patterning is the goal.

Nevertheless, it is there and we are interested in determining the effects to whatever level they occur (which could be negative or positive).

In some cases the presence of yaw could enhance scintillation (??) Alternately, Marty Haske is doing some fascinating studies on precise symmetry’s positive influence on the purity of dispersion. If his theories pan out, yaw could have a definite adverse impact when occuring in an otherwise super-symmetrical diamond.

In well patterned diamonds like you see on PS almost any yaw will be so slight that you’d not see anything overt in the Brilliancescope results - though some of us believe points of misdirected light from areas of yaw may be detected by BS…(hmm, a use for Brilliancescope)
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Date: 8/27/2005 12:16:08 AM
Author: belle

since i did not receive brian's masterwork gem file for free, i thought i'd try and fix leonid's diamond.......
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Belle, as the one clever enough to have quickly figured out the ACA image and fake proportions didn't match in that smear-job thread a while back - and as one who Garry proclaimed a DC master in the brilliancescope interference thread - I think you are very worthy of the gem file.
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PM me and I'll get it to you.

I looked at your adjustments. If you want to go much further here is a tip: Remember which is the most important view of all. It will reveal much. Do you still want to work on it some?


please do not throw me out the window!
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If we did you would float.
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No worries. We need more enthusiasts like you.
 
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