ASETs and fancy cuts

[Garry H (Cut Nut)]

GH> Finally, no one seems to be mentioning fancy coloured ASET - its the clasic example that John refers to as "in context", and here is an example of an ASET for a fancy colour - its not the best example - just one that I opened a few minutes ago. Its a DiamCalc from a bad scan.
The top image is from DiamCalc, middle is a vendor photo with no backlight, and below is the AGS digital ASET. It would be great to have an example with a good photo too? <GH
Bryan>Garry,
A question and a couple of comments.
What do you make of the large discrepancy between the DC and AGS ASET maps? Significantly more light return in top image.

Fancy colored diamonds are a different animal altogether than diamonds in the normal range from a cutting perspective. Therefore the ASET interpretations will be entirely different. In a FCD the cutter is aiming primarily for color and weight retention. The color call on the cert and carat weight will largely determine the value of the diamond. Therefore one might come to the conclusion from looking at ASET that this is a very well cut stone in the sense that brightness is damped down that would otherwise diminish the aparent color, and light is being drawn from the pavilion, which may help the color and assist in being able to enhance aparent color in setting by using a strategically closed and colored back.

These same techniques used on a diamond in the normal range would largely negate the beauty aspects important to value and sellability.<Bryan
Bryan perhaps you could help - I rarely have access to AGSL graded diamonds, and do not have AGS-PGS software - but you do on both counts, and I believe you have DiamCalc (if not send me scans). You also have an ASET set up - but I think it might only be ASET black.
So maybe that will not work - but at least we could compare AGS and DiamCalc images.

The aim with lighter colored FCD's is to keep them light (reducing the amount of blue in ASET or contrast from observer obstruction) and increasing the ray paths through the stone (looking down into a very tall glass of one of Johns beverages, vs thru the short side). Shorter ray paths like well cut RBC's are brighter and thats why Vivid rounds and emerald cuts are so crazy expensive. But Fancy Dark FCD's can be made more beautiful by improving the amount of ASET red (and holding off the ASET blue).

 

[MelisendeDiamonds]

In such threads heads still pound bricks over fundamentals many pages later.

More is more: 200 proof is the most intoxicating ABV. And RED is the most intense light return seen in ASET.

What's "better" is a matter of context and taste. But as a fundamental baseline of discussion - whether moonshine or diamond-shine - I submit that more simply means more in the repeatable structured environment being discussed in this thread.

Thanks John I haven't been here long but it does appear from this 24 page thread that last time this topic was discussed not much consensus was reached.

Diagem a cutter of fancy shapes of many different styles made the following comment in 2010:

https://www.pricescope.com/communit...ions-bad.148696/page-16#post-2700734#p2700734

The intensity of the direct light (red) vs mostly indirect (green).

I believe even AGS says a combination of both (more red than green) with some blue (obstruction & light return depending on position) is needed to have a balance of light intensities..., good brightness doesnt mean only Aset red as it doesnt mean Aset green only.

David, you didnt compare your "beautiful" radiant to another radiant with a better combination of Aset reds , greens & blues. Only then can we be more objective when we are talking about "very" brightness..., it has nothing to do with gorgeous though. But if we are talking pure brightness..., red will be brighter than green as a matter of fact.

Fast forward 4 years its most of the same arguments and the same positions with very little movement. Unfortunately for even the most learned on this forum this argument may well appear to be the "H&A" vendors versus the "ORC" vendors today unlike 4 years ago as few consumers are participating now.

I have no horse in this game, don't sell either, but I know the brands and where to find them. Yet I like this topic and the participation, we can all learn something from each other. I prepared this slide with the intention of comparing the two.



The one on the left is 25% more spready than the other.
The one on the left would be ~25% cheaper than the other.
The one on the left has faster scintillation than the other.

The one on the right is brighter and more brilliant than the other.
The one on the right has more fire than the other.
The one on the right has larger flashes than the other.

But the question here is, is the only way this information gets out to write an article?
A one sided monologue with my "opinion" because that is the only way a comparison of the pros and cons of the two cutting styles can be made free of a lot of unproductive trivial arguments and marketing?

 

[Texas Leaguer]

In such threads heads still pound bricks over fundamentals many pages later.

More is more: 200 proof is the most intoxicating ABV. And RED is the most intense light return seen in ASET.

What's "better" is a matter of context and taste. But as a fundamental baseline of discussion - whether moonshine or diamond-shine - I submit that more simply means more in the repeatable structured environment being discussed in this thread.

Thanks John I haven't been here long but it does appear from this 24 page thread that last time this topic was discussed not much consensus was reached.

Diagem a cutter of fancy shapes of many different styles made the following comment in 2010:

https://www.pricescope.com/communit...ions-bad.148696/page-16#post-2700734#p2700734

The intensity of the direct light (red) vs mostly indirect (green).

I believe even AGS says a combination of both (more red than green) with some blue (obstruction & light return depending on position) is needed to have a balance of light intensities..., good brightness doesnt mean only Aset red as it doesnt mean Aset green only.

David, you didnt compare your "beautiful" radiant to another radiant with a better combination of Aset reds , greens & blues. Only then can we be more objective when we are talking about "very" brightness..., it has nothing to do with gorgeous though. But if we are talking pure brightness..., red will be brighter than green as a matter of fact.

Fast forward 4 years its most of the same arguments and the same positions with very little movement. Unfortunately for even the most learned on this forum this argument may well appear to be the "H&A" vendors versus the "ORC" vendors today unlike 4 years ago as few consumers are participating now.

I have no horse in this game, don't sell either, but I know the brands and where to find them. Yet I like this topic and the participation, we can all learn something from each other. I prepared this slide with the intention of comparing the two.



The one on the left is 25% more spready than the other.
The one on the left would be ~25% cheaper than the other.
The one on the left has faster scintillation than the other.

The one on the right is brighter and more brilliant than the other.
The one on the right has more fire than the other.
The one on the right has larger flashes than the other.

But the question here is, is the only way this information gets out to write an article?
A one sided monologue with my "opinion" because that is the only way a comparison of the pros and cons of the two cutting styles can be made free of a lot of unproductive trivial arguments and marketing?

I think your approach is exactly what is needed. You provide meaningful technical data and context. And if you then combine your expert real world assessment of the visual appearance of the stone it would be great. I think that is what teobdl intended by starting this thread as a re-focus from an earlier discussion. If you could provide ASET to go along with it, that would make it complete.

I also think you have to do your best to push through some of the nonsense. That is always part of the rough and tumble of an open forum.

 

[Rockdiamond]

I do not agree that Fancy Colored Diamonds are "a different animal"
I'd say FCD's are different breed of the same animal, with a tremendous amount of crossbreeding.
Positive attributes of each style have made their way into the other.
For example, I see a lot more of the world's major cutters of FCDs designing cushions and radiant cuts with smaller table/higher crown combos.
This does a number of things from an optical perspective, and we'll get into as we look at stones.
But the point is, when buying a Fancy Colored Diamond a lot of what draws me to the stone are things that draw me to a colorless stone.

 

[John P]

Thanks John I haven't been here long but it does appear from this 24 page thread that last time this topic was discussed not much consensus was reached.

You're welcome. There are a number of well-meaning threads like this which come to loggerheads. The obstacles tend to be different interpretations of same-terms, limitations of this medium (kudos to Sergey for working to transcend this) and unavoidable complexity of science and data mixing with taste factors and dependency on environment.

The upside is occasional interesting, out-of-box ideas. The downside is the spinning of wheels in such a way that mud sometimes flies

The intensity of the direct light (red) vs mostly indirect (green).

I believe even AGS says a combination of both (more red than green) with some blue (obstruction & light return depending on position) is needed to have a balance of light intensities..., good brightness doesnt mean only Aset red as it doesnt mean Aset green only.

David, you didnt compare your "beautiful" radiant to another radiant with a better combination of Aset reds , greens & blues. Only then can we be more objective when we are talking about "very" brightness..., it has nothing to do with gorgeous though. But if we are talking pure brightness..., red will be brighter than green as a matter of fact.

That's a nice summary by Yoram. My own correlations agree with what he posted.

...Unfortunately for even the most learned on this forum this argument may well appear to be the "H&A" vendors versus the "ORC" vendors today unlike 4 years ago as few consumers are participating now...

I'm not sure about that. The subject of the thread invokes fancy cuts, specifically. I've only seen MRBs mentioned as a reference-standard for AGSL, which consensus that complex fancy shapes must be treated differently.

Relative to that, I made observations on page 1 which remain unchanged. It's possible they'll stay that way after another 24 pages, but I'm certainly open to learning.

https://www.pricescope.com/community/threads/asets-and-fancy-cuts.204414/#post-3720558#p3720558

...Now let's reverse-engineer the process. For rounds it's especially reliable. I've done so much work with rounds and princess cuts in real-life, and have become so familiar with how XYZ paremeters pan-out, that I'm quite comfortable making interpretations from an ASET and a grading report. For more complex and variable fancies it gets harder. The qualifier here is the need to reverse-engineer; meaning the most important component to ASET interpretation with fancies is prior live correlation.

So for hobbyists who never see diamonds ASET theory and interpretation can still be useful with round brilliants, as there's reliable consistency in "reading" particulars of brightness, contrast and leakage. For diamond pros who make daily correlations of diamonds to ASET it's certain that even more can be intuited. But complex fancy shapes are different, even for pros. And for hobbyists who haven't made regular (daily/abundant/diverse) correlations to real-life viewing it's possible to misinterpret or "read too much" into a fancy ASET image.

 

[Rockdiamond]

Melisende Diamonds, all due respect, but for someone "with no horse in this game" you certainly seem to focus on me, and my position.
In fact, there were no other tradespeople participating in that thread 4 years back because Stan Grossbard is hesitant to get involved- it's not easy to be the only one taking a position.
I did not start the current thread- or the one of last week- they are spurred on by consumers who have questions.
As far as Diagem, we have discussed this topic at great length. I can't speak for him, but I've refined my position quite a bit due to my discussions with him- and other respected cutters.
One thing that is apparent to me is that to really do something special with a diamond cut, the cutter needs to have single minded approach = at least when cutting that specific type of diamond. Therefore a cutter who really specializes in a certain cut will necessarily have strongly held positions. Like an artist.
I know that two cutters with differing visions will agree on many things- but there's going to be a lot of areas where each takes a different path, and yes, disagrees.
Can we please keep a positive tone?
The diagrams you posted are valuable to the conversation, we'll be using actual stones as models which will put things into even more context

 

[Rockdiamond]

Let me just throw this out there to all the pros posting:
What is your opinion of AGSL Fancy Shape Cut Grading?

 

[Texas Leaguer]

Let me just throw this out there to all the pros posting:
What is your opinion of AGSL Fancy Shape Cut Grading?

David,
Rather than throw it out here, why don't you start a seperate thread?
For the record, I am only familiar with the princess cut grading model and I think it is excellent. I believe if AGS had more reach, it would fundamentally change the way princess cuts are manufactured.

 

[Rockdiamond]

Brian, the reason it is relevant to this thread is that ASET and AGSL grading are inexorably tied together.

 

[Karl_K]

Let me just throw this out there to all the pros posting:
What is your opinion of AGSL Fancy Shape Cut Grading?

princess is somewhat useful the rest is useless mainly because it does not take into account visual patterns and off axis lighting and is too much RB centric. Tilt is not the same as off axis lighting. The contrast model it badly implemented and grossly over simplified.
I think in most cases it is counter productive.
Sure Octavia gets 0 LP SE by a wide margin but it was never a design consideration of mine and if it didn't I would not change a thing about the optics to get it.
We did change the girdle slightly to get the 0 in proportions for marketing reasons but if it had impacted the optics it would not have been done.

 

[Texas Leaguer]

Brian, the reason it is relevant to this thread is that ASET and AGSL grading are inexorably tied together.

David,
This thread is supposed to be about interpretation of ASET images of fancy shape diamonds. We are simply talking about ASET maps and photos along side stone data and expert descriptions of the real world visuals of the diamonds. If we stay focused around that goal, the discussion could possibly yield fruit.

For this discussion think of ASET as a simple viewer. You use a loupe because it gives you information about what is going on in the stone regarding clarity. Using a loupe in and of itself does not predudice your evaluation of clarity any more than looking through the ASET tool predudices you about light performance. It simply reveals additional information which you take into account along with other pertinent information for a full understanding of the diamond.

 

[Texas Leaguer]

Let me just throw this out there to all the pros posting:
What is your opinion of AGSL Fancy Shape Cut Grading?

princess is somewhat useful the rest is useless mainly because it does not take into account visual patterns and off axis lighting and is too much RB centric. Tilt is not the same as off axis lighting. The contrast model it badly implemented and grossly over simplified.
I think in most cases it is counter productive.
Sure Octavia gets 0 LP SE by a wide margin but it was never a design consideration of mine and if it didn't I would not change a thing about the optics to get it.
We did change the girdle slightly to get the 0 in proportions for marketing reasons but if it had impacted the optics it would not have been done.

Well, I guess that is some validation for the model that your precision designed and crafted fancy is graded properly by the AGS system.

Can you explain the distinction between tilt and off-axis lighting? I think I may have used the term incorrectly earlier.

 

[John P]

Brian, the reason it is relevant to this thread is that ASET and AGSL grading are inexorably tied together.

Structured light environments existed long before AGSL published their approach.

1970s: Diamond Grading Microscope (Okuda)
1980s: Proportion Loupes (Zeiss, Nikon, R&S)
1984: Firescope (Tamura & Shigetomi, Eightstar)
1990: Hearts & Arrows Viewer (Yamashita)
1998: Gilbertsonscope (Gilbertson, GIA)
2001: Ideal-Scope (Holloway)
2003: SymmetriScope (Eightstar, based on Gilbertson & Firescope)
2005: ASET (AGSL, based on Gilbertson)

All of the structured environments above (minus H&A) give information about where a diamond draws its light and (either) returns it to the viewer's eye or passes it through the stone. The standout feature of ASET for fancies, as with the GS predecessor, is graduated coding which includes low-angle draw.

Edited to add:

You use a loupe because it gives you information about what is going on in the stone regarding clarity. Using a loupe in and of itself does not predudice your evaluation of clarity any more than looking through the ASET tool predudices you about light performance. It simply reveals additional information which you take into account along with other pertinent information for a full understanding of the diamond.

Posted as I was composing mine. Precisely.

 

[Karl_K]

Well, I guess that is some validation for the model that your precision designed and crafted fancy is graded properly by the AGS system.

Can you explain the distinction between tilt and off-axis lighting? I think I may have used the term incorrectly earlier.

But can it be used to find others that are well cut, that is where it falls down.
There is just too much variation in what makes an outstanding diamond with fancies to great a usable model as whats good. If you could you would still have the issue of it being sensitive enough and mssing important things.
I view cut grades and ASET as a sorting tool, the many to one.
That is where it falls down. All is not lost it can provide useful info if kept in context.

Tilt is when the diamond is tilted and the pavilion is not pointed directly towards the viewer.
Of axis lighting is when the light is coming from areas not parallel to the table while the pavilion is pointed towards the viewer. How wide an area the diamond draws and returns viewable light to the viewer while static would be my definition of off axis capability.

Due to the design of an RB that is a relatively small area. With step cuts because of the different orientation of the reflectors it can be a wider area and also more possible to design for both on and off axis lighting because you have more divergent light paths to work with.
Each of the pavilion steps draws light from different angles in a step cut because they are at different angles where the pavilion/lgf angle is fixed for the depth of the pavilion in an RB.

 

[Rockdiamond]

John, and Bryan- part of the reason we go back and forth on certain issues is a differing philsohpy.
Take the AGSL 0 princess cut.
They are incredible stones, and remarkably consistent in a world of mish mash bad attempts.
In that, I can see tremendous value added.
But I'd be so totally bummed if all cutters cut princess cuts to AGSL 0 proportions.

Just like the amazing Octavia- which I love in real life- I would not want all people cutting asschers to try and copy Karl's design.

That, for me is the issue with AGSL fancy cut grading- it's far to single minded.
I know that a perfectly cut Original Radiant Cut will get poor marks using AGSL principles.
Having seen the stones, and understanding what goes into stones cut for LP and stones cut for scintillation- like an ORC, I appreciate both.
That means the principles which downgrade stones cut for scintillation are based on faulty assumptions- such as where many diamonds actually get their light.
Comparing ASET to a loupe misses the point IMO.
A loupe confirms what your eye sees- with aset we need to go in the other direction.
Take what our eyes see and calibrate the interpretation of ASET to match what our eyes tell us.
It's possible to select and grade diamonds without an ASET- but not without a loupe.

 

[Texas Leaguer]

John, and Bryan- part of the reason we go back and forth on certain issues is a differing philsohpy.
Take the AGSL 0 princess cut.
They are incredible stones, and remarkably consistent in a world of mish mash bad attempts.
In that, I can see tremendous value added.
But I'd be so totally bummed if all cutters cut princess cuts to AGSL 0 proportions.

Just like the amazing Octavia- which I love in real life- I would not want all people cutting asschers to try and copy Karl's design.

That, for me is the issue with AGSL fancy cut grading- it's far to single minded.
I know that a perfectly cut Original Radiant Cut will get poor marks using AGSL principles.
Having seen the stones, and understanding what goes into stones cut for LP and stones cut for scintillation- like an ORC, I appreciate both.
That means the principles which downgrade stones cut for scintillation are based on faulty assumptions- such as where many diamonds actually get their light.
Comparing ASET to a loupe misses the point IMO.
A loupe confirms what your eye sees- with aset we need to go in the other direction.
Take what our eyes see and calibrate the interpretation of ASET to match what our eyes tell us.
It's possible to select and grade diamonds without an ASET- but not without a loupe.

You could grade diamonds without a loupe too. You just wouldn't be as good at it.

 

[Rockdiamond]

I have to disagree Bryan.
There's no way to grade clarity, to GIA or AGSL standards without a loupe.

 

[MelisendeDiamonds]

If you could provide ASET to go along with it, that would make it complete.

I also think you have to do your best to push through some of the nonsense. That is always part of the rough and tumble of an open forum.

Okay here you go.





To avoid any confusion the right hand side is a photograph of the actual diamond.

 

[Texas Leaguer]

I have to disagree Bryan.
There's no way to grade clarity, to GIA or AGSL standards without a loupe.

Exactly. That's why you use the right tools for the specific goals you wish to achieve. For assessing how a diamond is handling light ASET is a useful tool - If you understand what it does and does not do for you. For instance, it is no help in clarity grading.

 

[Rockdiamond]

If you could provide ASET to go along with it, that would make it complete.

I also think you have to do your best to push through some of the nonsense. That is always part of the rough and tumble of an open forum.

Okay here you go.





To avoid any confusion the right hand side is a photograph of the actual diamond.

Great stuff!
Here's (yet) another issue this raises.
Photography.
Clearly there's a different method used for each stone.

My experience is that each type of stone requires different methods to accurately capture.
Still, for the purposes of discussion, is it possible to photograph each diamond in an identical setup?

 

[Texas Leaguer]

If you could provide ASET to go along with it, that would make it complete.

I also think you have to do your best to push through some of the nonsense. That is always part of the rough and tumble of an open forum.

Okay here you go.





To avoid any confusion the right hand side is a photograph of the actual diamond.

How would you describe each of those diamonds in terms of visual effects and eye appeal in different lighting. (I'm really not trying to make work for you - I am just curious as I do not have as much experience with these shapes.)

I think for the purposes of this particular thread it would be interesting to understand the real life properties of the top one. The ASET would be considered weak by many people because of all the white. But it does appear to have a good distribution of red and green and the actual image of the stone looks like it would be pretty.

 

[Garry H (Cut Nut)]

Sergey posted this graphic to show how a great ASET can give bad optical results. Here I have added an ETAS image – it shows where the stone can get and return light to a cyclops observer. I think this is what Karl means when he says ‘off axis lighting”

Also on the previous page 2 - Bryan, while you were all sleeping, I posted some things that have been ignored???

 

[Karl_K]

Sergey posted this graphic to show how a great ASET can give bad optical results. Here I have added an ETAS image – it shows where the stone can get and return light to a cyclops observer. I think this is what Karl means when he says ‘off axis lighting”

ETAS can show a difference in the ability to return off axis lighting but I haven't come up with a simple way of explaining ETAS that I am happy with.
This is going to take us way off topic so maybe we should save it for another time or thread.

 

[Garry H (Cut Nut)]

Sergey posted this graphic to show how a great ASET can give bad optical results. Here I have added an ETAS image – it shows where the stone can get and return light to a cyclops observer. I think this is what Karl means when he says ‘off axis lighting”

ETAS can show a difference in the ability to return off axis lighting but I haven't come up with a simple way of explaining ETAS that I am happy with.
This is going to take us way off topic so maybe we should save it for another time or thread.

I was not proposing a discussion about ETAS Karl, but the idea that a stone can have great ASET and ideal-scope images, but if the stone does not work "off Axis" then it can turn from beauty to ugly duckling with far more dramatic consequences than a diamond that is able to return light from a wider and better range of azimuths (not just angles).

Does this example show better what off axis lighting means?

 

[Karl_K]

Does this example show better what off axis lighting means?

Yes that is pretty good way to show one aspect of it.
Can you post the standard DC tolk with that lighting?

 

[Serg]

.

 

[Garry H (Cut Nut)]

Does this example show better what off axis lighting means?

Yes that is pretty good way to show one aspect of it.
Can you post the standard DC tolk with that lighting?

As close as I can get Karl, because I did not save the setup.

 

[Texas Leaguer]

Sergey posted this graphic to show how a great ASET can give bad optical results. Here I have added an ETAS image – it shows where the stone can get and return light to a cyclops observer. I think this is what Karl means when he says ‘off axis lighting”

Also on the previous page 2 - Bryan, while you were all sleeping, I posted some things that have been ignored???

Garry,
We have been moving computers around in the office and I do not have access to any of the tools at the moment. They promise to have me set up when I get back from my vacation. Hopefully I will be able to catch up soon. You guys are over my head at the moment. But don't let me hold the class back-please carry on.

 

[Karl_K]

ETAS RB showing narrow area it is drawing light from.
What this shows is you basically put the diamond inside a sphere and map where it is is drawing light that is returnable to the eye.

 

[Karl_K]

Here is Octavia showing a much wider range of light draw.
The second image is a side view of the ETAS sphere.
Remember how I have been saying that "leakage" is for the most part the diamond drawing light from the pavilion and not leakage like a window? The dots in the red lined area are the pavilion are "leakage" in the second image.