AGS ASET Info and Photos from JCK

[Midnight]

Neil,

Nice images!!! Can you please clarify where the light source is coming from in the handheld ASET with the light tray vs. the tablet desk model? It appears the light source from the light tray goes from the bottom through the PAVILLION side and then to the hand held ASET. In contrast, the light source in the tablet desk model is coming from the bottom, I think, then through the CROWN side and then is blocked by the cap. Am I correct? The handheld does not require any cap? A little confused!

 

[denverappraiser]

On the tabletop model, the cone is about 5 inches in diameter with the wide opening pointing straight up. There is a plate of glass over the opening and the stone rests table down on the glass. There is a mirror system to allow the viewer to look from directly below the stone without needing to lie on the floor. The lighting comes from overhead and is the ambient light in the room. There is a small plastic cap that rests over the top of the stone to block off transmitted light.

The handheld unit is very similar to an idealscope in appearance and operation where the cone is about 1.5 inches in diameter. The stone is held at the plane of the cone and the viewer looks through a peephole in the middle of the blue area through the table of the stone using the ambient room lighting. With the light tray, the stone is resting table up in a hole that is slightly smaller than the stone in a translucent piece of plastic. The light is from below and the viewer is looking straight down from above the tool. There is a small piece of black tape on the back of the plastic sheet that blocks off the transmitted light but allows light around it to enter the cone. With the idealscope, this is absent. With this approach there is no piece of glass between the camera and the stone but it’s wickedly difficult to arrange the viewing angle to be perpendicular to the table of the stone. Tiny variations are apparently important.

Neil Beaty
GG(GIA) ISA NAJA
Independent Appraisals in Denver

 

[DiamondExpert]

Great pics Neil!

I have found that the best focus plane for diamonds sitting in the cone of the plastic plate of the flat light is not with the ASET resting on the plate, but just above it (2-3mm). I am assuming (perhaps incorrectly) that the bottom edge of the ASET should be in the same plane as the girdle of the diamond...let me know if this is wrong. I''m sure this will vary then with the size (depth) of each diamond, which could be a real problem in trying to achieving consistency of angle.

Of course, with the ASET slightly above the glass plate you get more extraneous light coming in from the sides and I suspect screwing up the image. Also, if you just let the ASET rest on the plate each time you do an image, the angles will be different for each diamond due to the differences in each stones'' height.

Perhaps I''m wrong headed here, but this seems like a major and inherent problem in the current setup...let me know.

Cheers,

 

[denverappraiser]

This is probably the case but I sure hope you''re wrong.

The most recent set of pics I posted have the opening of the cone on the same plane as the table of the stone. The previous few are actually moved away from the cone because of the thickness of the glass. Moving closer would require a completely different setup and, assuming the stone is resting on it''s table, will vary depending on the size of the stone and the height of the crown. The tabletop unit has no calibration for this although the piece of glass is inset into to the cone so I strongly suspect that they''ve defined the top surface of the glass as the plane for the table. This callibration is the reason that Garry has several photo trays in his system. The difference in the various trays is how the stone sits relative to the edge of the cone. I have no way of knowing if the cone in the tabletop unit is the same geometry as the handheld and I''m too cheap to drop $1000 to get one. When they come out I''m confident that someone here will buy one, take it apart and measure it for us (Rhino?). This is another area where there''s a distinct benefit to using a bigger instrument. A 1mm variation will have a smaller effect.

Neil

 

[WinkHPD]

Date: 6/9/2005 12:04:00 PM
Author: denverappraiser
There is a definate tendency to see more in this kind of image than is actually there but used with care I''m starting to think I''m going to like this thing. Here''s a picture of the same stone that is reasonably well centered and resting on a very thin piece of plastic. I think the different tone of green around the edges is caused by uneven lighting and the faint shadow of the cap I used to block off the transmitted light.

Niel,

I think I recall hearing that some of the slight variations in color can be caused by how close to the border of the angles the light is coming from but I do not remember with enough certainty to state whether that is light close to the horizon or close to the 45 degrees that turns the brownish green color. I will state that with the second shot I would never have ventured my guess that this would not be an AGS 0 cut. It is REALLY much prettier without the tilt.

Your pictures are getting much better, my applause for what is probably taking hours and hours of your time!

Wink

 

[denverappraiser]

Wink,

Thanks for the kind words. Practice seems to help. Lots of life works like that

I just noticed that in the two pictures, one has the green dot and one does not. This is surely the result of the effect that Gary was commenting on! In the first picture, the girdle of the stone is just inside the edge of the cone and in the second picture it's just outside.

Neil

 

[lostdog]

"In my opinion, part of the beauty of the ASET is the ability to look at a picture and KNOW many things about the diamond without all the things that you were talking about above. It is meant, I believe, to be a guide to the light proformance of the stone that will give you INSTANT visual knowledge about how the stone is treating light that it receives."

You are right in that one simple visual would work very well, but I think that's true a lot more for professionals who have viewed many of these. The images are a bit more complex for somebody with limited experience but good intentions, which probably covers just most consumers, even the advanced ones.

So beyond checking for the basic arrangements of facets and so on, which though apparent in a few of the most recently posted examples would also have been basically clear in an idealscope, and in several of those cases, through a loupe with natural light, a consumer trying to apply those images to his purchase decision is going to wonder what the images tell.

So some sort of analysis of that image might be helpful, not as a replacement for the image, but as a learning experience. The geometries and colors can play tricks on the eyes. And, for example, isn't this system set up so that the areas of greatest light return come back in red, while "leakage" (I'm glossing over the detailed semantics) is white. (If Dark Red in the image represents bright (approximately white) in the real stone, then the physiology of the eye responds to the images artificial colors with different, and to some degree inverted, sensitivity to reality.)

Certainly I think you can learn to see the ASET image properly, with experience. Still, again this treads into the territory where people also compare low HCA scoring diamonds. You've already used it as a tool to screen out "95%" or "99%" of other stones, so it's natural to want to continue using it to compare and learn about your short-listed stones.

My thought was that if you could characterize something about the image, let's say for the lack of a better example at the moment it's the ratio of red to green to white, possibly in different zones (table, star, kite facets, etc.; or inner, middle, outer; or some other way), it might be that you can relate this to other characteristics. Not instead of the image, but as a way for interested consumers to learn about the system.

I suppose somebody could come up with a detailed tutorial based solely on the visuals that would help. I know for the idealscope that the information available on the web is only a bare start, and one instantly comes up against situations that it does not explain. So the more helpful thing is to hang around PS and watch some experts critique from time to time when images are posted.

The ASET looks even more complicated to become fluent with than the Idealscope. Not too complicated for people to understand, but suddenly it's not single value red versus white analysis.

 

[WinkHPD]

Agreed, it would be nice if some of the big dogs could call AGS and lean on them to come play here. Then we all could learn mountains more, consumer, prosumer and professionals all need help with this brand new and exciting toy!

Paul Antwerp, please call Peter Yantzer and lean on him to assign one of his resident geniuses to come play with us!

Wink

 

[JohnQuixote]

Wow Neil. Impressive.

 

[adamasgem]

Date: 6/4/2005 2:33:12 AM
Author: Garry H (Cut Nut)
Well done Sir John.
They have done a great job at AGS.
But Jim missed the Tokowsky - it should be the next one down on the chart.

The center of the stone should be green below 40.768 degrees pavilion angle, as my memory serves

(Tolkowsky arrived at 40.75 degrees)
But then that would be splitting hairs, except that we know that the laws of physics do not allow for any exteraneous bending of light (not even for stressed diamonds)

Gary: If the "laws of physics do not allow for extraneous bending of light (not even for stressed diamonds)" , then how do you explain visible strain patterns under crossed polars (and sometimes without).

You are not dealing with a homogeneous and "perfect" lattice structure.

Additionally, and I think it has been in other published literature by AGS, and should be made clear, that the ASET charts published to date by AGS, were exemplars for one size stone only (6mm), and that the retail ASET tool and hand held offers a "qualitative" look at the stone, its'' symmetry, and where it is grabbing its'' light from, which varys slightly with the size of the stone relative to a fixed colored illumination field.

There is much more going on when AGS generates results for their reports, as they take into account these size effects for angles of colored light incidence.

 

[Garry H (Cut Nut)]

Actually DiamCalc accounts for that Marty - these are the same Tolkowsky crown and pav 40.75 angles but one is 4mm and one is 14mm.
Any way it appears the DiamCalc image does exactly the same thing as the hand held unit does as the diamond size varies. Cute huh?

I have always assumed DiamCalc works from the girdle plain - should we ask Sergey or Vlad?

Re stress - take some Valium

 

[denverappraiser]

Working from the girdle plane seems like a fairly serious problem because the stone is resting table down on a surface that can’t be adjusted (or even worse, hand held in a pair of tweezers). For a tool that’s only 38mm tall, a 1-2mm variation in the crown height can make a significant alteration in the angles presented. Since we’re claiming an accuracy in the thousands, this is a monstrous margin of error. I’m not smart enough at this time of day to work out the math but I wouldn’t be surprised if it adds a fudge factor of more than a degree.

Neil Beaty
GG(GIA) ISA NAJA
Independent Appraisals in Denver

 

[WinkHPD]

Date: 6/9/2005 7:41:58 PM
Author: denverappraiser

Working from the girdle plane seems like a fairly serious problem because the stone is resting table down on a surface that can’t be adjusted (or even worse, hand held in a pair of tweezers). For a tool that’s only 38mm tall, a 1-2mm variation in the crown height can make a significant alteration in the angles presented. Since we’re claiming an accuracy in the thousands, this is a monstrous margin of error. I’m not smart enough at this time of day to work out the math but I wouldn’t be surprised if it adds a fudge factor of more than a degree.

Neil Beaty
GG(GIA) ISA NAJA
Independent Appraisals in Denver

I am beginning to regret that I threw out that number. Peter shared it with us as an example of how incredible his math whiz guys were, not to start a controversy about whether or not the green table reflection was a good or bad thing. (It is not!)

I think that the table model will be an incredible boon to those of us who want a repeatable picture, every time, with no tilt other than any tilt of the table itself.

I think we will be working from the table plane as that is how the tool is designed for the table model. with the hand held model we will be working at or near the girdle plane, depending on how the stone fits in the hole of the light holder. The basic picture may change a little, but not too much I am thinking. We will still know, at a glance, a LOT about the stone and the details can come later with the appropriate testing equipment if desired.

Wink

Wink

 

[Garry H (Cut Nut)]

I guess the point is that id does not matter if you use the hand held and tweezers with a little variation - Sit the stone table down on glass, or use 3D models - the tiny variation is not that critical.

All 3 methods can be different.

I still theoretically prefer not to use table centered as the pavilion is the prmary symmetry grade maker (ie the 40.5 to 41.5 degree pavilion angle H&A''s stones)

 

[JohnQuixote]

Date: 6/9/2005 6:57:50 PM
Author: adamasgem

Additionally, and I think it has been in other published literature by AGS, and should be made clear, that the ASET charts published to date by AGS, were exemplars for one size stone only (6mm), and that the retail ASET tool and hand held offers a 'qualitative' look at the stone, its' symmetry, and where it is grabbing its' light from, which varys slightly with the size of the stone relative to a fixed colored illumination field.

There is much more going on when AGS generates results for their reports, as they take into account these size effects for angles of colored light incidence.

Marty, just so.

There are logical simplifications. In addition to your deviation observations, adjustments are made for binocular perception of obscuration at 25cm (for instance). By taking 30 degrees & 40 degrees of obscuration it simplifies the baseline in case stereopsis is in question. For purposes of this metric AGS has concluded that it works.

 

[JohnQuixote]

Date: 6/9/2005 7:28:56 PM
Author: Garry H (Cut Nut)

Actually DiamCalc accounts for that Marty - these are the same Tolkowsky crown and pav 40.75 angles but one is 4mm and one is 14mm.
Any way it appears the DiamCalc image does exactly the same thing as the hand held unit does as the diamond size varies. Cute huh?

I have always assumed DiamCalc works from the girdle plain - should we ask Sergey or Vlad?

It seems that the 25cm distance is inferred as the constant, eye to table.

 

[denverappraiser]

I practiced my old trigonometry skills, which are almost non-existent, and tried to work out the change in the angles depending on the placement of the stone relative to the cone. It looks to me like moving the stone 2mm inward from the girdle plane will have a 3.2 degree shift in the angle leading to the demising line between the pink and the green. Moving 2mm out will have a similar effect. This means that the edge of the green is at 45 degrees (plus or minus 3.2) depending on which tool and which viewing technique is used. With the standard lightbox approach, the girdle will be a few mm inside the cone and resting on a plate like the desktop unit it will be a few mm outside. My choice of 2mm was arbitrary but it seemed like decent starting point. With larger stones this will actually be more.

Placing the stone at some location other than the exact center of the tool has a similar effect. A 2mm misplacement seems to result in a whopping 6.0 degree variation in the angle to the pink/green line as viewed on opposing sides of the cone.

Neil Beaty
GG(GIA) ISA NAJA
Independent Appraisals in Denver

 

[Serg]

.

 

[Garry H (Cut Nut)]

Date: 6/10/2005 9:01:21 AM
Author: denverappraiser

I practiced my old trigonometry skills, which are almost non-existent, and tried to work out the change in the angles depending on the placement of the stone relative to the cone. It looks to me like moving the stone 2mm inward from the girdle plane will have a 3.2 degree shift in the angle leading to the demising line between the pink and the green. Moving 2mm out will have a similar effect. This means that the edge of the green is at 45 degrees (plus or minus 3.2) depending on which tool and which viewing technique is used. With the standard lightbox approach, the girdle will be a few mm inside the cone and resting on a plate like the desktop unit it will be a few mm outside. My choice of 2mm was arbitrary but it seemed like decent starting point. With larger stones this will actually be more.

Placing the stone at some location other than the exact center of the tool has a similar effect. A 2mm misplacement seems to result in a whopping 6.0 degree variation in the angle to the pink/green line as viewed on opposing sides of the cone.

Neil Beaty
GG(GIA) ISA NAJA
Independent Appraisals in Denver

I will trust your math is correct Neil.
BTW a 1.08ct stone has a 1mm crown heght.
A 2mm crown height = about 9ct
So size does matter if we are playing hair splitting.

But the calculation you did neil is probably a bit simplisitic - it assumes the diamond is at the center of the focus point - in actual fact the diameter of the table should also be taken into account.
It is more complex than I can manage.

Marty you have phd's from MIT
Can you help us?

 

[adamasgem]

Date: 6/9/2005 7:28:56 PM
Author: Garry H (Cut Nut)
Actually DiamCalc accounts for that Marty - these are the same Tolkowsky crown and pav 40.75 angles but one is 4mm and one is 14mm.
Any way it appears the DiamCalc image does exactly the same thing as the hand held unit does as the diamond size varies. Cute huh?

I have always assumed DiamCalc works from the girdle plain - should we ask Sergey or Vlad?

Re stress - take some Valium

The only that stresses me out is, when I asked a direct question, in reply to your statement about stress in diamonds, is that you choose to ignore or acknowledge that you might be giving out misleading or incorrect information, and resort to talking about DiamondCalc renderings.

If the modeling is "somewhat" correct, any reverse ray trace image will appear "correct" or "similar", that wasn''t the issue I was addressing.

 

[Garry H (Cut Nut)]

Since we are digressing Marty, would you like to discuss this stone I saw today in the Smitsonian?
If you want to then we will start another thread - because already we are diverting this one.

The stone appeared even more to the eye than to the camera to have second or third order dispersion colors. It had "muddy dispersion".
I never saw it before?

But i think I know why.

 

[adamasgem]

Date: 6/10/2005 5:43:58 PM
Author: Garry H (Cut Nut)

Date: 6/10/2005 9:01:21 AM
Author: denverappraiser

I practiced my old trigonometry skills, which are almost non-existent, and tried to work out the change in the angles depending on the placement of the stone relative to the cone. It looks to me like moving the stone 2mm inward from the girdle plane will have a 3.2 degree shift in the angle leading to the demising line between the pink and the green. Moving 2mm out will have a similar effect. This means that the edge of the green is at 45 degrees (plus or minus 3.2) depending on which tool and which viewing technique is used. With the standard lightbox approach, the girdle will be a few mm inside the cone and resting on a plate like the desktop unit it will be a few mm outside. My choice of 2mm was arbitrary but it seemed like decent starting point. With larger stones this will actually be more.

Placing the stone at some location other than the exact center of the tool has a similar effect. A 2mm misplacement seems to result in a whopping 6.0 degree variation in the angle to the pink/green line as viewed on opposing sides of the cone.

Neil Beaty
GG(GIA) ISA NAJA
Independent Appraisals in Denver

I will trust your math is correct Neil.
BTW a 1.08ct stone has a 1mm crown heght.
A 2mm crown height = about 9ct
So size does matter if we are playing hair splitting.

But the calculation you did neil is probably a bit simplisitic - it assumes the diamond is at the center of the focus point - in actual fact the diameter of the table should also be taken into account.
It is more complex than I can manage.

Marty you have phd''s from MIT
Can you help us?

1) I have a Bachelors and Master''s in Aero/Astro from MIT, not a piled high and deep, but did spend 18 years there in research and development, but wasn''t narrowly focused like most PhD''s

2) Since I don''t have the dimensions of the device, I can''t work out the angles..
The crown height (CH%) percentage is a function of the table size percentage (T%) and crown angle(CA)
Percentages are 0 to 100 in this formula below:

Tan(CA)= CH%/(50-0.5*T%)

CH=diameter*CH%

The weight of the stone will additionally depend on the girdle plane thickness, star facet length, pavilion angle, break facet lengths, culet size, etc as well as symmetry and diameter.

A medium girdle Tolkowsky stone of about a carat will have a depth percentage of about 61.7%

BUT, what you see in the ASET tool will depend not only on the centering, symmetry and size, BUT on other factors on how the stone is cut, like pavilion angles, pavilion break facet lengths, star facet lengths,and crown break facet style..

 

[adamasgem]

Date: 6/10/2005 6:15:35 PM
Author: Garry H (Cut Nut)
Since we are digressing Marty, would you like to discuss this stone I saw today in the Smitsonian?
If you want to then we will start another thread - because already we are diverting this one.

The stone appeared even more to the eye than to the camera to have second or third order dispersion colors. It had ''muddy dispersion''.
I never saw it before?

But i think I know why.

Gary: Move the question and picture to the Fire Performance Scope thread.. It is a complicated issue, and depends on the lighting environment and the cut of the stone, plus a lot of other factors..

 

[valeria101]

Date: 6/10/2005 6:15:35 PM
Author: Garry H (Cut Nut)

The stone appeared even more to the eye than to the camera to have second or third order dispersion colors. It had ''muddy dispersion''.

Is that double refraction in that photo ?

 

[RockDoc]

Date: 6/10/2005 6:57:38 PM
Author: valeria101

Date: 6/10/2005 6:15:35 PM
Author: Garry H (Cut Nut)

The stone appeared even more to the eye than to the camera to have second or third order dispersion colors. It had ''muddy dispersion''.

Is that double refraction in that photo ?

Diamonds are not double refractive..... so it is not double refraction.

Not seeing the stone in person I can ONLY GUESS WHAT IT MIGHT BE..

I have a suspicion that it COULD BE EYE VISIBLE STRAIN ( or stress). Some times strain appears very clear - other time it is what I call showdowy, but that could be what Gary is referring to as muddy.

It is sort of uncommon to observe strain with out crossed polaroids, but there are some diamonds which do show visible strain. To some, this can be confused with dispersion or spectral colors in the stone.

I have heard others call this biregrigence, but that is a property or characteristic of DR. More properly in a sort of slang terminology it could be more properly called Anomolous DR.

The view of Gary''s photo isn''t a really good view.... but I sort of have a gut feeling that it has "blast off" strain when viewed with crossed polaroids.. BUT THAT IS JUST A GUESS ON MY PART.

Rockdoc

 

[valeria101]

Date: 6/10/2005 7:19:29 PM
Author: RockDoc

Diamonds are not double refractive..... so it is not double refraction.

The view of Gary's photo isn't a really good view.... but I sort of have a gut feeling that it has 'blast off' strain when viewed with crossed polaroids.. BUT THAT IS JUST A GUESS ON MY PART.

Well, I wasn't thinking of a new species of diamond... the picture shows double lines of everything, as if it were a chunk of calcite, not diamond, hence the Q. The original post implies, but does not spell out that the thing in the picture is a diamond !

Once upon a time I was shown a small diamond showing sort of over the top dispersion (I was going to say play of color, but that's absurd!, the seller described it as "opalescent" believe it or not). I didn't and still do not know how to id strain without any tools. The piece was also very hazy throughout. Garry's picture reminded me the marquise in question.

Thank you for the guess

another guess might be twinning... which the odd shape of the thing suggests

Garry ! ?

 

[Rhino]

Date: 6/9/2005 1:32:04 PM
Author: DiamondExpert
Great pics Neil!

I have found that the best focus plane for diamonds sitting in the cone of the plastic plate of the flat light is not with the ASET resting on the plate, but just above it (2-3mm). I am assuming (perhaps incorrectly) that the bottom edge of the ASET should be in the same plane as the girdle of the diamond...let me know if this is wrong. I''m sure this will vary then with the size (depth) of each diamond, which could be a real problem in trying to achieving consistency of angle.

Of course, with the ASET slightly above the glass plate you get more extraneous light coming in from the sides and I suspect screwing up the image. Also, if you just let the ASET rest on the plate each time you do an image, the angles will be different for each diamond due to the differences in each stones'' height.

Perhaps I''m wrong headed here, but this seems like a major and inherent problem in the current setup...let me know.

Cheers,

I''m finding the same thing too Gary. What makes this more difficult is that critical angle of 40.76 as there are many super ideals/ideals cut with angles right in that zone. If the center eye (green or red) is going to be an indicator of greater or less than the 40.76 it is important that the images reflect this gemological truth. I gotta catch up more in this thread but I gotta know if Garry H. has found out if the image is supposed to be taken at girdle plane or table plane. The images I have taken in the past through our red reflector, which most accurately reflect DiamCalc results/images were taken at girdle plane.

If the more accurate way to examine the stones is *above* girdle plane (as it will be in the desktop ASET) then we all need to be viewing stones through our ASET raised slightly above table (or the thickness of the glass that will be used in desktop ASET).

 

[JohnQuixote]

Date: 6/10/2005 9:44:26 PM
Author: Rhino

I'm finding the same thing too Gary. What makes this more difficult is that critical angle of 40.76 as there are many super ideals/ideals cut with angles right in that zone. If the center eye (green or red) is going to be an indicator of greater or less than the 40.76 it is important that the images reflect this gemological truth. I gotta catch up more in this thread but I gotta know if Garry H. has found out if the image is supposed to be taken at girdle plane or table plane. The images I have taken in the past through our red reflector, which most accurately reflect DiamCalc results/images were taken at girdle plane.

If the more accurate way to examine the stones is *above* girdle plane (as it will be in the desktop ASET) then we all need to be viewing stones through our ASET raised slightly above table (or the thickness of the glass that will be used in desktop ASET).

This question of table versus girdle is 'on the list,' as is the 'green eye 40.77 question (40.768 rounded, right Jon?

).

As to that: The large chart I have shows green in the eye of the table for all rounds with a PA
I've asked AGS if I can post these illustrations, but have not heard back yet.

 

[Garry H (Cut Nut)]

Sorry guys - whatever method, hand held, sitting on glass or DiamCalc - whatever you use, the whole system will give different colour for the same pavilion angle depending on a host of stone dependant variables. You are trying to get too much out of the instrument.

You are all being a bit anal over 40.768.

It does not matter - the instrument tells us additional good info.

(for the record - it would be good if we could put this baby to sleep - anyone want to win a prize for getting the reasons why the greatest variable is the stone - not hand held, Desk Top or DiamCalc?)

 

[valeria101]

Date: 6/10/2005 11:08:17 PM
Author: Garry H (Cut Nut)

... get the reasons why the greatest variable is the stone - not hand held, Desk Top or DiamCalc ?

One version...

These tools and systems do not seem to contradict each other - actually, from where I stand, they seem to just tweack slight details from green to red and back without adding all that much to the platter.

Interestingly, one immage keeps recurring - that top "arrows" image of a very symmetrycal and very optimized round diamond. One can only guess that if any spectacular (not to say meanigful) difference between the results (or performance) of these asessment tools does persist, it would become apparent on a richer, more diverse sample of subjects. So, keeping the object of observation so narrowly defined could have been the "greatest variable", or well, the independent one.

Insofar DiamCalc has the potential to model anything, the others might but there is not much to go for.