AGS New Round Stone Cut Grade System for 2005

[beryl]

Sorry to interrupt. I just became aware of this thread and have not yet read it through. However, I saw this color map which is similar to many I have seen before, and thought it worthwhile to show the head obscuration limits on it, which explain why the favored proportions are near the upper boundary of the ''best'' stones. The dark boxes, I understand, are AGS'' new grading zones.

Old timers note that I have switched from my infamous term ''obstruction'' to ''obscuration'', which Peter Yantzer pointed out is more appropriate because of its optical connotation and usage; Garry no longer need be bothered by visions of childbirth problems.

 

[beryl]

Once again I goofed-up loading a pic. Here's the 4th try.

Edit 6AM: and this didn't work either - 4 titles now - all in there but not out here. Sorry. I tried.

Edit 7AM: 10° obscuration can be approximated by a straight line from P/C=39.6°/40° to 41.7°/28°. This corresponds to bezel-to-table rays (and vice-versa) at a viewing distance of about 12". This skims the lower edge of the AGS boxes; they are well-aware of this limitation. Red things below this line are not as good as they appear on the map.

5° by line from P/C= 39.5°/38.5° to 41.25°/28°.

0° by line from P/C= 39.5°/36.1° to 40.8°/28°. The viewer sees his head at any distance.

Leonid: What am I doing wrong? Can you post one of the 'accepted' pics, such as 'HCA-FL.jpg'

 

[niceice]

Our opinion on the new AGS cut grade system is that the AGS has sold out to the pressure placed upon them by the cutters to expand the parameters of the AGS Ideal Cut proportions rating so that the cutters can cut diamonds bulkier to retain more weight and still obtain an ideal cut rating. There, we said it.

The AGS and the GIA laboratories may be "non profit" however as with all non-profit organizations they are definitely concerned about their bottom line. Diamond grading reports = $$$ and the fact is that many diamond cutters have pulled away from the AGS Laboratory over the past year as the price of diamond rough increased in favor of the GIA who at present is not indicating the crown and pavilion angle averages on their lab reports which makes it easier for the diamond cutters to bluff the public with near ideals which are cut with a table diameter within the range for the ideal cut rating and an acceptable total depth in hopes that most of the public won''t look past that information for the crown and pavilion angle measurements - and most won''t so the hedge on that bet is quite good.

Nobody wants to send a diamond to the AGS Laboratory if it''s going to be graded as a one or a two cut because it causes the public to realize that something better is available. When paper was introduced to the diamond market, it caused the public to ask questions and demand more of their jewelers and the fact of the matter is that it was not a welcome change.

So the price of rough is up and cutters are producing diamonds with girdle facets which are being pushed for weight and a wider range between the high and low measurements for the pavilion and crown angle measurements in an attempt to hit the magic combinations of average crown and pavilion angle that the public has been taught to look for and now the AGS is expanding the parameters of their proportions system to allow another thirty something percent more diamonds into the ideal cut classification - was it 37%? That seems familiar... Somehow this just doesn''t seem all that surprising to us, it feels like a direct response to the concept of Economics 101 - when sales dip, adapt to the everchanging market and re-design the parameters of a well established system.

In truth, we have always hoped that the AGS would revamp their guidelines for the ideal cut rating, but we kind of hoped that they would tighten it not expand it.

We would be fine with this, perfectly fine with this, IF the expansion of the proportions criteria were based upon the evaluation of ACTUAL DIAMONDS which had been measured for Brilliance, Dispersion and Scintillation. But as we understand it, this is all based upon Wire Frame and Virtual modeling and while that can be a valid indication of POTENTIAL we don''t feel that it should be the basis for a Cut Grade System. Forgive us, but doe Anime Cartoon Girls look and act anything like real women? No and neither do virtual diamonds.

We''re going to treat the new Ideal Cut Classification from the AGS just as we did with the original... We''re going to accept it as a suggested range for a classification and we will continue to purchase diamonds based upon the actual visual performance of those diamonds and not upon a piece of paper which states that the proportions of the diamond are "ideal" which leads the public to believe that the visual performance of the diamond is going to be optimum or "ideal" simply because a virtual model leads them to believe that it will be... Based upon our own research conducted on actual diamonds brought in for physical evaluation over the years, we know that minor variations between the combination of proportions can cause substantial reductions in light return.

Will expanding the parameters of the AGS ideal cut proportions scale by 37% decrease the public''s chance of buying a beautiful and lively diamond by 37%? That remains to be seen.

 

[niceice]

New news... It is our understanding that the AGS may have already tightened their original proposal of the new cut system and IS using a Helium as part of their evaluation process which would give them a more substantial understanding of the facet by facet relationship of the diamond! That would improve their ability to virtual model the diamond and estimate the potential of the diamond... A definite step in the right direction IF that analysis is paired with an actual measure of the light return of the actual diamond... Perhaps a double safety type of system. But virtual modeling alone is not sufficient in our opinion and certainly not if the modeled position of the viewer and the light source is not absolutely perfect. The release of the new cut system in 2005 should certainly be interesting in comparison to the results on paper and real life.

 

[adamasgem]

Date: 11/12/2004 12

1:16 PM
Author: niceice
New news... It is our understanding that the AGS may have already tightened their original proposal of the new cut system and IS using a Helium as part of their evaluation process which would give them a more substantial understanding of the facet by facet relationship of the diamond! That would improve their ability to virtual model the diamond and estimate the potential of the diamond... A definite step in the right direction IF that analysis is paired with an actual measure of the light return of the actual diamond... Perhaps a double safety type of system. But virtual modeling alone is not sufficient in our opinion and certainly not if the modeled position of the viewer and the light source is not absolutely perfect. The release of the new cut system in 2005 should certainly be interesting in comparison to the results on paper and real life.

Todd, that is my understanding also.

I like you comment "that will improve their ability to virual model the diamond and extimate the POTENTIAL of the diamond"

The problem with your statement "paired with an actual measure of th elight return of the actual diamond", is that, for the "data" to be meaningfull, that "measuremnt" must be taken in a realistic and acceptable lighting environment, otherwise it is just a "number" which may or may not relate to performance under typical viewing conditions, and I don''t mean viewing conditions in a jewelry store either, something the consumer will see once in a lifetime, but viewing conditions underwhich the wearer of the ring will typically encounter in their everyday life, at the office, at a dinner or at home.

Thats where the power of accurate modeling comes to bear, as it is sometimes extremely difficult to make such a physical environment for "measurements", per se. Nothing that I know of on the market replicates these environments for "brilliance", regardless of the marketing spin put on these devices.

In my "hijacked thread" we are discussing these issues, vis-a-vie modeling approaches..

https://www.pricescope.com/community/threads/ags-new-cut-grade-system-early-2005.19268/

 

[beryl]

One last try - per Garry''s suggestion (invalid characters in title).

 

[Garry H (Cut Nut)]

This is Beryl''s chart.

A few cooments re AGS. R&T after years of seeing and using HCA you must have thought I was crazy and deluded (true, I know) to suggest that a diamond with a crown anle of 30 degrees could look as beautiful as one of 34.5 dgerres. The fact is that they can and do. They look different to what you are used too, but they appeal to some that have never bought diamonds before. AGS have fixed their parametric grading system, they have not loosened it.

 

[Garry H (Cut Nut)]

I put this up in another thread.

It does not include all GIA possabilities - it is an interpretation based on some ranges they give in their Fall 2004 G&G article.

R&T it would seem like the polt to delude is thicjening

 

[niceice]

Marty, note that we said: "But virtual modeling alone is not sufficient in our opinion and certainly not if the modeled position of the viewer and the light source is not absolutely perfect." thereby acknowledging the dilemma with the concept of the viewer...

Gary buddy, we''re not surprised by the 30 degree crown angle concept, we''ve noticed that the shallow crown angles are not as critical to the performance of a diamond as long as the pavilion angle is on target while steep crown angles seem to be less appealing to our taste. Actually we seem to recall that one day we akk agreed that a diamond would look quite interesting and lively without any crown at all didn''t we?

 

[Garry H (Cut Nut)]

Date: 11/12/2004 11:21:19 PM
Author: niceice

Marty, note that we said: ''But virtual modeling alone is not sufficient in our opinion and certainly not if the modeled position of the viewer and the light source is not absolutely perfect.'' thereby acknowledging the dilemma with the concept of the viewer...

Gary buddy, we''re not surprised by the 30 degree crown angle concept, we''ve noticed that the shallow crown angles are not as critical to the performance of a diamond as long as the pavilion angle is on target while steep crown angles seem to be less appealing to our taste. Actually we seem to recall that one day we akk agreed that a diamond would look quite interesting and lively without any crown at all didn''t we?

So R&T, what is it that makes you unhappy about AGS''s new appraoch?

(BTW I doubt a diamond with no crown would be interesting or lively - it may be very bright and boring though)

 

[adamasgem]

I overlaid the old GIA 1990''s cut classification ranges on the sides of Gary''s plot, the 55 table would be in GIA''s idea rangel, and I converted the pavilion depth #''s of GIA to pavilion angles(for a zero culet) for this plot

 

[Garry H (Cut Nut)]

Interesting Marty - I never saw it presented that way.

Robin & Todd?
What do you not like?

 

[Garry H (Cut Nut)]

doubleup

 

[Garry H (Cut Nut)]

Some people ask why HCA recomends such shallow stones.
It is because I believe a good diamond should be viewed from 16 inches or 40cm.
AGS believe in the 25cm near 10 inch US military standard.
I have modeled diamonds as viewed with a 6inch head blocking lights from each of those viewing distances.
One is just off the bottom of the AGS 0 range. The lower stone is just off the bottom of the HCA ideal range (2.4).
Now Peter Yantzer believes that any stone that meets their new standard simply must be a good stone. I concur. But to say that a stone that returns light from even more directly above is not a good diamond? Welll, sorry, I think a stone of say 34.5C and 40 degree pavilion is a nice stone (except for fat headed people).

 

[strmrdr]

Date: 11/15/2004 6:39:48 AM
Author: Garry H (Cut Nut)


It is because I believe a good diamond should be viewed from 16 inches or 40cm.

I believe a good diamond should be viewed and computer modeled on someones hand in real world lighting, conditions and distances.
All the studies are fine but the question is what do they look like on the hand in the real world?
None of the studies/research has came close to answering that question.
It is sad that Marty, niceice and myself are the only ones that seem to be screaming that here and were not getting heard.
My challenge is model me what a diamond looks like in the real world on the hand not what it looks like in the lab.

16 inch distance is better than 10 in that regard but the whole head shadow sidetrack throws it off.

 

[adamasgem]

Date: 11/15/2004 7:32:49 AM
Author: strmrdr

Date: 11/15/2004 6:39:48 AM
Author: Garry H (Cut Nut)



It is because I believe a good diamond should be viewed from 16 inches or 40cm.

I believe a good diamond should be viewed and computer modeled on someones hand in real world lighting, conditions and distances.
All the studies are fine but the question is what do they look like on the hand in the real world?
None of the studies/research has came close to answering that question.
It is sad that Marty, niceice and myself are the only ones that seem to be screaming that here and were not getting heard.
My challenge is model me what a diamond looks like in the real world on the hand not what it looks like in the lab.

16 inch distance is better than 10 in that regard but the whole head shadow sidetrack throws it off.

Strmrdr, Trust me we are getting heard

Some in the trade may not like the message..

One of the problems in "backing" off of the viewer''s position is that the narrowed Field of View, while, with using backward ray trace methodogies, seemingly gives valid data, the restricted viewpoints are revealed in forward montecarlo studies to have some peculiar problems, which I''ll address later, probably on the other more technical thread on Pricescope.

I 100% agree that if part of the buying decision is based on paper, it should not be based on paper which is full of holes..

 

[adamasgem]

Date: 11/15/2004 5:13:34 AM
Author: Garry H (Cut Nut)
Interesting Marty - I never saw it presented that way.

Robin & Todd?
What do you not like?

Just a perspective of older thought patterns, clearly showing the widening of grades, maybe based on some erroneous assumptions