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Which cert captures the most information on cut?

Rockdiamond

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bqd251|1446922977|3946694 said:
Rockdiamond|1446842915|3946405 said:
About the science, here's one example- "our world is lit from above"
An irrelevant statement, even if it wasn't broadly inaccurate.

This affects many other conclusions such as ASET interpretation of "red is better than green"

I'm not a scientist, but I have though so much about this.
Is a direct reflection of light better than a reflected reflection?
The direct reflection is likely brighter- but is that necessarily better?

If the light is entering the diamond through the crown ( green in ASET) it's far more likely to bounce around the diamond before exiting. Seems intuitive that means the light must loose intensity as it bounces.
But when looking at actual stones that have a lot of dispersed green- or a well cut RBC non H&A with a more "mottled" ASET - sometimes the fact that there's more flashes of light compensates for the additional brightness of a larger, directly reflected light beam.


Sorry, but you're quite clearly making assertions or conclusions that aren't true. It stems from your misunderstanding of how light rays function. As a result you aren't correctly interpreting ASET maps.

Are you claiming light entering from the table is more directly reflected back through the table? If so then why do Idealscope images often show the area under the table to be the lightest shades of red or even pink -shouldn't they be the deepest red? Afterall, aren't IS images supposed to measure intensity of light return?
Maybe you have studied light but not necessarily diamonds. From my perspective it is your misunderstanding of how diamonds actually perform in real life. I'm not " interpreting aset maps- I'm looking at, and buying thousands of diamonds a year- many of which I've examined with ASET. Reality, as opposed to maps.
Real diamonds in real life environments sometimes disprove some of the assertions commonly made here which I've already specified.

I never mentioned IS as its not relevant to the points I'm making.
Is your world "lit from above?"
 

Rockdiamond

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sharonyanddave|1446934464|3946776 said:
Rockdiamond|1446836437|3946355 said:
I'm not a scientist, but I have been looking at and working with diamonds my entire adult life- the AGSL cut grading system is missing a vital component regarding scintillation.

From a scientific perspective Sassian and AGSL did a lot of work on scintillation I know that the 15 degree tilt dataset that they chose for many metrics is in part derived from the fact that scintillation events in a round brilliant occur in greatest frequency between 0 and forward tilt of 15 degress.

However a conscious decision was made not to 'grade' scintillation or include a large part of the original research which utilized scintillation maps because preferences based on scintillation are highly subjective. Whether one prefers a smaller number of slower and larger flashes or a large number of smaller and faster flashes is a preference that an objective system based on optical science should not decide.

Rockdiamond|1446836437|3946355 said:
My experience is that there's a disconnect between AGSL cut grading, and scintillation.
There is no connection whatsoever and it is intentional.
Rockdiamond|1446836437|3946355 said:
AGSL rewards larger bright reflections

The word larger should be removed from this sentence.

I think this is where you are misinterpreting their system, the brightness metric makes deductions for the surface area of the crown that is not capable of returning high angle light. It makes no distinction between a large flash or a small one. An Old European Cut (OEC) with larger, broader and slower flashes or a Star108 with very small, faster flashes can receive the AGSL top grade just like the Modern Round Brilliant Tolkowsky Cut.
Ok- I stand corrected about the size of flashes.
Other than that it sounds like what you're saying is that AGSL chose to exclude scintillation research/results simply because the results are more subjective.
This is a large part of what I'm saying. If you're a person who loves scintillation events in diamonds, you need to look past AGS, as they have not been willing to or able to develop a metric for scintillation
 

sharonyanddave

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Rockdiamond|1446836437|3946355 said:
This is a large part of what I'm saying. If you're a person who loves scintillation events in diamonds, you need to look past AGS, as they have not been willing to or able to develop a metric for scintillation


I can't make sense of this statement, I wrote above that designs with numerous small and fast scintillation events are still capable of receiving the AGSL top grade for LP (e.g. Star108).

The AGSL system is a deduction system, and there is no deduction for scintillation, it is too subjective to say diamonds without "fast scintillation" should be penalized. It is not the place of a grading lab to say monochrome pinfire flash is better than fewer big bold colored flashes, that comes down to a taste preference.

I think where a lot of diamonds are penalized in their system is in the brightness and fire categories and it has nothing to do with their type of scintillation.

It would be more instructive to run a few diamonds of your preference through AGS-PGS and view specific examples rather than discussing in generalities and speculation.
 

Texas Leaguer

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sharonyanddave|1446934464|3946776 said:
Rockdiamond|1446836437|3946355 said:
I'm not a scientist, but I have been looking at and working with diamonds my entire adult life- the AGSL cut grading system is missing a vital component regarding scintillation.
From a scientific perspective Sassian and AGSL did a lot of work on scintillation I know that the 15 degree tilt dataset that they chose for many metrics is in part derived from the fact that scintillation events in a round brilliant occur in greatest frequency between 0 and forward tilt of 15 degress.
However a conscious decision was made not to 'grade' scintillation or include a large part of the original research which utilized scintillation maps because preferences based on scintillation are highly subjective. Whether one prefers a smaller number of slower and larger flashes or a large number of smaller and faster flashes is a preference that an objective system based on optical science should not decide.
Rockdiamond|1446836437|3946355 said:
My experience is that there's a disconnect between AGSL cut grading, and scintillation.
I think this is where you are misinterpreting their system, the brightness metric makes deductions for the surface area of the crown that is not capable of returning high angle light. It makes no distinction between a large flash or a small one. An Old European Cut (OEC) with larger, broader and slower flashes or a Star108 with very small, faster flashes can receive the AGSL top grade just like the Modern Round Brilliant Tolkowsky Cut.
Sharonyanddave,
From what I understand you articulate the AGSL position accurately and succinctly.

Scintillation research continues in earnest at AGSL. It is a complicated aspect of diamond performance and beauty, and one that has enormous computational requirements. Most importantly, as you point out, it is an area where tastes vary widely.

I do think that eventually AGSL will add reporting on scintillation to their evaluations. But it may never be in the form of a grade per se.
 

Rockdiamond

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sharonyanddave|1447004924|3947058 said:
Rockdiamond|1446836437|3946355 said:
This is a large part of what I'm saying. If you're a person who loves scintillation events in diamonds, you need to look past AGS, as they have not been willing to or able to develop a metric for scintillation


I can't make sense of this statement, I wrote above that designs with numerous small and fast scintillation events are still capable of receiving the AGSL top grade for LP (e.g. Star108).

The AGSL system is a deduction system, and there is no deduction for scintillation, it is too subjective to say diamonds without "fast scintillation" should be penalized. It is not the place of a grading lab to say monochrome pinfire flash is better than fewer big bold colored flashes, that comes down to a taste preference.

I think where a lot of diamonds are penalized in their system is in the brightness and fire categories and it has nothing to do with their type of scintillation.

It would be more instructive to run a few diamonds of your preference through AGS-PGS and view specific examples rather than discussing in generalities and speculation.
Hi Sharonyanddave, I am quite curious as to your ability to "speak for" AGSL...in fact there have been efforts at broadening the scope of the AGSL cut grade that surely you or Bryan know nothing about. This is a fact, although I can not be more specific.
But if you are speaking for AGSL- please clarify this statement
However a conscious decision was made not to 'grade' scintillation or include a large part of the original research which utilized scintillation maps because preferences based on scintillation are highly subjective.
What preferences about cut are NOT subjective?

You mentioned the "Star108"

Let's compare that to a Radiant Cut Diamond.
Someone interested in promoting Star108 cut it so that it would fit into AGSL "mold".
A well cut radiant cut does not fit into this same mold- and when radiant shaped stones ARE cut to gain AGSL top cut grades, they look nothing like what a well cut radiant should look like based upon what the inventor of the radiant design
The "crushed ice" stones being sold by Tiffany's, Harry Winston and many others follow the scintillation goals of the Original Radiant.
How popular is the Star108 compared to the Radiant Cut?
The market is speaking LOUD and CLEAR.
It would be better fr everyone if AGSL could narrow the gap and take market share from GIA
 

sharonyanddave

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Rockdiamond|1447004924|3947058 said:
Hi Sharonyanddave, I am quite curious as to your ability to "speak for" AGSL..

I don't speak for the lab, I speak to the lab. When was the last time you did that? See this cut and paste of an e-mail from Jason Quick.

What happened to the Scintillation maps those are not used as grading criteria?

Scintillation is still an active area of research. Scintillation is tricky to quantify and even trickier to incorporate into a grading system, therefore the scintillation maps are not used as grading criteria. Generally, a change in a design that increases the average number of scintillation events will simultaneously decrease the average size of the virtual facets. It’s a matter of personal taste which design is better, hence the difficulty in incorporating scintillation maps/metrics in the grading system.


Rockdiamond|1447004924|3947058 said:
in fact there have been efforts at broadening the scope of the AGSL cut grade that surely you or Bryan know nothing about.

AGSL is very approachable, and open, and willing to work with companies on optimizing new or current designs. From what I read here In May 2015 samples of the type of Radiant you prefer were submitted to the lab, perhaps instead of vague promotional references Radiantman would like to share the developments(if any) in a more educational manner.

However I sincerely hope that doesn't mean AGSL will subvert their standards and cowtow to any company trying to use their name as a marketing tool just to receive their grading business.

Radiant cuts in general have yield and spread requirements and to achieve these requirements requires shallow pavilions, allowing this design unaltered to receive the lab's top grade would in my opinion compromise the integrity of the entire AGSL grading system. The balancing constraints of a particular brand (yield and spread) with the AGSL LP standards is undoubtedly a challenge in the type of diamonds you prefer. I'd be interested to see if a compromise between the two was possible.
 

Rockdiamond

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I have spoken with both Jason and Peter pretty recently.
Are you writing as a consumer or are you in the trade?
We are all operating above board here- if you're a trade member please post it.
 

sharonyanddave

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Rockdiamond|1447256419|3948191 said:
I have spoken with both Jason and Peter pretty recently.
Are you writing as a consumer or are you in the trade?
We are all operating above board here- if you're a trade member please post it.

https://www.pricescope.com/communit...ormation-on-cut.216734/#post-3946158#p3946158

Still not in trade, but thanks for being the second trade member who has asked in this thread about my credentials.
I have no intention present or future to sling diamonds, I think there are easier ways to make money.

That still doesn't stop me from having open dialogue with members of the lab and others members of the diamond trade.
The diamond industry has developed a bad rap by poorly informing customers and being "secretive" and "proprietary" about information.
Pricescope goes a long way to dispel that stereotype but I find some of your responses in this thread do the opposite.
If you have more recent information to share about AGSL research or grading than by all means share it.
 
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