Princess Apples to Apples on cut b/t GIA and AGS?

[phade]

Hi All -

I''m having some issues trying to pick out a nice stone. Been looking at Princess exclusively in the .7-.9 range. Seen some AGS 0, 1, and 3, cuts at a local jeweler.

I''ve also looked online at Whiteflash, JA, etc. and checked out what they have. My problem is I see many GIA stones that look promising and can''t make apples to apples comparisons between them and the AGS stones as far as cut. I understand that GIA is reputable, but I don''t want to drop the ball on cut.

Visually, the AGS 0 is nice and the 1 is quite as nice as well and I have a hard time telling the difference in my untrained eye. I can see a slight difference in the AGS 3 cuts. I know the lucky lady won''t be complaining one bit, but personally, I''d like to stick with a AGS 0 or 1 cut.

I know Whiteflash has their ACA and GoG has their nice stones, but how do I determine/rate the GIA stones from places like JA, etc.?

 

[Todd Gray]

You''re going to have to work closely with each vendor to determine whether the GIA graded princess cut diamonds are comparable in terms of visual performance to those graded by the AGS as Ideal 0 for light performance. Frankly, I''ve gotten to the point where I don''t even bring in princess cut diamonds for evaluation unless they are graded AGS Ideal 0 because I''ve grown tired of paying for shipping to open the box and go, ugh, disappointed (again)... but that''s just me, maybe other vendors are having a better time of it. The fact that the crown and pavilion sections of a princess cut diamond have two major sections each make it practically impossible to predict visual performance "by the numbers" which is why I''m truly partial to AGS grading under the Platinum platform which includes a rating for Light Performance.

Pay close attention to the facet structure of the diamond, especially on the underside, because the number of chevron facets located on the lower (pavilion) half of the diamond have a major effect on the size and number of the virtual facets and thus the overall visual performance of the diamond... I''m partial to a two chevron structure, some people prefer three, four and so on... The smaller the virtual facets, the smaller the flashes of light will be, the more difficult it will be for you to see fire from the diamond - instead you''ll see more brilliance... I prefer to see a mix of both and a two chevron facet structure provides this (for my eyes).

 

[stone-cold11]

The most you can do is ask for ASET images for the GIA stones.

 

[Lorelei]

Date: 5/12/2010 12:37:10 PM
Author:phade
Hi All -

I'm having some issues trying to pick out a nice stone. Been looking at Princess exclusively in the .7-.9 range. Seen some AGS 0, 1, and 3, cuts at a local jeweler.

I've also looked online at Whiteflash, JA, etc. and checked out what they have. My problem is I see many GIA stones that look promising and can't make apples to apples comparisons between them and the AGS stones as far as cut. I understand that GIA is reputable, but I don't want to drop the ball on cut.

Visually, the AGS 0 is nice and the 1 is quite as nice as well and I have a hard time telling the difference in my untrained eye. I can see a slight difference in the AGS 3 cuts. I know the lucky lady won't be complaining one bit, but personally, I'd like to stick with a AGS 0 or 1 cut.

I know Whiteflash has their ACA and GoG has their nice stones, but how do I determine/rate the GIA stones from places like JA, etc.?

Hi Phade,

Really your best bet is to stick to AGS0 or GIA graded Princess which have been hand selected for their superior optical performance and beauty by a vendor that is passionate about and is an expert on cut quality. That should narrow the field then you can select between these according to visual and other preference. James Allen and some of the other vendors can supply ASET and other images in order for you to choose.

 

[WinkHPD]

Date: 5/12/2010 1:59:10 PM
Author: Lorelei

Date: 5/12/2010 12:37:10 PM
Author:phade
Hi All -

I''m having some issues trying to pick out a nice stone. Been looking at Princess exclusively in the .7-.9 range. Seen some AGS 0, 1, and 3, cuts at a local jeweler.

I''ve also looked online at Whiteflash, JA, etc. and checked out what they have. My problem is I see many GIA stones that look promising and can''t make apples to apples comparisons between them and the AGS stones as far as cut. I understand that GIA is reputable, but I don''t want to drop the ball on cut.

Visually, the AGS 0 is nice and the 1 is quite as nice as well and I have a hard time telling the difference in my untrained eye. I can see a slight difference in the AGS 3 cuts. I know the lucky lady won''t be complaining one bit, but personally, I''d like to stick with a AGS 0 or 1 cut.

I know Whiteflash has their ACA and GoG has their nice stones, but how do I determine/rate the GIA stones from places like JA, etc.?

Hi Phade,

Really your best bet is to stick to AGS0 or GIA graded Princess which have been hand selected for their superior optical performance and beauty by a vendor that is passionate about and is an expert on cut quality. That should narrow the field then you can select between these according to visual and other preference. James Allen and some of the other vendors can supply ASET and other images in order for you to choose.

While you may have some luck going with hand selected GIA stones, if you ever intend to resell a princess based on great cutting you will either need a good buy back or trade in policy with your vendor, or you will need an AGS paper on your princess. Since GIA has no cut grade system for princess cuts you can never use the expertise of your vendor when YOU are trying to resell your diamond.

Todd covered it pretty well in his statement. For cut grading on princess cuts there is only one top tier lab doing any grading of them for cut.

Wink

 

[Todd Gray]

Date: 5/12/2010 1:29:16 PM
Author: Stone-cold11
The most you can do is ask for ASET images for the GIA stones.

And the problem with attempting to apply the ASET scope concept to diamonds not graded by the AGS Laboratory is that the view from an ASET scope as seen from the 90 degree view straight down is that it only provides some insight into the optical symmetry of the diamond at that one specific vantage point - at which point, you might as well just look at the Ideal Scope image because the depth of the imagery is about the same - a single static view of the diamond as seen from a 90 degree angle. However the intent behind the ASET scope is entirely different than the purpose of the Ideal Scope... The Ideal Scope was developed to assist people with determining the optical symmetry of the diamond and to determine to what extent the diamond might be leaking light; the ASET scope was developed to judge the potential brightness of the diamond and it is used by the AGSL in conjunction with in-depth mathematical ray tracing (actual reverse ray tracing) which judges the results from more than 200 vantage points or degrees of tilt. Thus using an ASET to look at a GIA graded diamond in an attempt to determine whether it might be comparable to another diamond deemed to be AGS Ideal 0 by the AGS for Light Performance, Polish, Symmetry and Proportions is like saying "uh, yea, that''s a car" but without really having any in-depth idea about the potential the car has in terms of performance.

The only people who can wield the AGS ASET Scope with any degree of accuracy, are the people at the AGS Laboratory because only they are capable of conducting the full ray tracing analysis using the ASET platform; and the results can only be found on the AGS Platinum Diamond Quality Document; anybody else attempting to draw a correlation between a diamond as seen through an ASET scope and the Light Performance grade developed by the AGS Laboratory is essentially defrauding the consumer by way of misrepresentation!

 

[denverappraiser]

The AGS ray tracing software is available to dealers and appraisers for a fee and they can use a Sarin scan and the AGS software to make a pretty good estimation if a stone has the right proportions for an AGS-0 cut grade. As is pointed out above, odds are against. Why? Because if they were, the original cutter didn’t arrive at those proportions by accident and they would have sent the stone to AGSL instead of GIA for grading because they would be hoping to sell it for a premium due to the AGS-0 pedigree. The only reason to send an AGS-0 princess to GIA for grading is if you don't know that's what you've got and, frankly, this strikes me as terribly unlikely.

Neil Beaty
GG(GIA) ICGA(AGS) NAJA
Professional Appraisals in Denver

 

[Todd Gray]

Date: 5/12/2010 4:43:37 PM
Author: denverappraiser
The AGS ray tracing software is available to dealers and appraisers for a fee and they can use a Sarin scan and the AGS software to make a pretty good estimation if a stone has the right proportions for an AGS-0 cut grade. As is pointed out above, odds are against. Why? Because if they were, the original cutter didn’t arrive at those proportions by accident and they would have sent the stone to AGSL instead of GIA for grading because they would be hoping to sell it for a premium due to the AGS-0 pedigree. The only reason to send an AGS-0 princess to GIA for grading is if you don't know that's what you've got and, frankly, this strikes me as terribly unlikely.

Neil Beaty
GG(GIA) ICGA(AGS) NAJA
Professional Appraisals in Denver

This is true Neil, and as you might imagine, the AGS PGS software is loaded on my computer; however as you and I both know the AGS assessment is primary based on their ASET 'system' which is not the same as the face-up view which is referred to above by Stone Cold 11 and by many other people here on PS 'continually' as a point of the 'online consideration process' used to determine whether a diamond should remain of interest or not... So I guess I'm driving the point home a little bit harder than necessary by saying that (even with the software) I think that the only entity which should refer to a diamond as having AGS Ideal 0 Light Performance is the AGS Laboratory; but then again, I also consider the range of possibility for what is "ideal cut" as defined by the AGSL themselves is too broad and think that allowing factions other than the AGS Laboratory to say "this is equivalent to AGS Ideal 0" especially in terms of their Light Performance grade is opening the door wide open for the 'system' to be abused by less desirable elements of the trade who might look to cheat the system by simply cutting to produce diamonds which look good when considered 'by consumers' by the face-up (only) view as provided by the ASET scope when in reality trade members like ourselves know that important elements such as fire (dispersion) and scintillation are NOT even considered in the assessment of the AGS Light Performance grade (!) which is why I feel it important to work with reputable dealers who take ALL factors of visual performance and cut precision into account.

I honestly don't think that the AGS PGS should be used be dealers to make that assessment because too many variables exist outside the sanctity of the AGSL grading environment with regard to potential abuse for mis-use of the PGS - I believe the intention of the AGSL to allow trade members to purchase use of the software was to improve the cutters ability to produce diamonds which will meet the new standards set forth by the performance grade; and to assist dealers with deciding which diamonds to send to the AGS; but I do not believe that the AGSL intended the software to be used on the selling floor to entice consumers into purchasing diamonds which are not graded by the AGSL on the Platinum Light Performance platform "but are just like diamonds that are"

 

[ChunkyCushionLover]

Date: 5/17/2010 12:11:14 PM
Author: Todd Gray

Date: 5/12/2010 4:43:37 PM
Author: denverappraiser
The AGS ray tracing software is available to dealers and appraisers for a fee and they can use a Sarin scan and the AGS software to make a pretty good estimation if a stone has the right proportions for an AGS-0 cut grade. As is pointed out above, odds are against. Why? Because if they were, the original cutter didn’t arrive at those proportions by accident and they would have sent the stone to AGSL instead of GIA for grading because they would be hoping to sell it for a premium due to the AGS-0 pedigree. The only reason to send an AGS-0 princess to GIA for grading is if you don't know that's what you've got and, frankly, this strikes me as terribly unlikely.

Neil Beaty
GG(GIA) ICGA(AGS) NAJA
Professional Appraisals in Denver

This is true Neil, and as you might imagine, the AGS PGS software is loaded on my computer; however as you and I both know the AGS assessment is primary based on their ASET 'system' which is not the same as the face-up view which is referred to above by Stone Cold 11 and by many other people here on PS 'continually' as a point of the 'online consideration process' used to determine whether a diamond should remain of interest or not... So I guess I'm driving the point home a little bit harder than necessary by saying that (even with the software) I think that the only entity which should refer to a diamond as having AGS Ideal 0 Light Performance is the AGS Laboratory; but then again, I also consider the range of possibility for what is 'ideal cut' as defined by the AGSL themselves is too broad and think that allowing factions other than the AGS Laboratory to say 'this is equivalent to AGS Ideal 0' especially in terms of their Light Performance grade is opening the door wide open for the 'system' to be abused by less desirable elements of the trade who might look to cheat the system by simply cutting to produce diamonds which look good when considered 'by consumers' by the face-up (only) view as provided by the ASET scope when in reality trade members like ourselves know that important elements such as fire (dispersion) and scintillation are NOT even considered in the assessment of the AGS Light Performance grade (!) which is why I feel it important to work with reputable dealers who take ALL factors of visual performance and cut precision into account.

I honestly don't think that the AGS PGS should be used be dealers to make that assessment because too many variables exist outside the sanctity of the AGSL grading environment with regard to potential abuse for mis-use of the PGS - I believe the intention of the AGSL to allow trade members to purchase use of the software was to improve the cutters ability to produce diamonds which will meet the new standards set forth by the performance grade; and to assist dealers with deciding which diamonds to send to the AGS; but I do not believe that the AGSL intended the software to be used on the selling floor to entice consumers into purchasing diamonds which are not graded by the AGSL on the Platinum Light Performance platform 'but are just like diamonds that are'

Although omitted in the platinum reports of AGS 0 stones the categories of contrast and dispersion are measured and a weighted average is measured in PGS and will be shown in the report of non AGS 0 stones.
Here is a AGS PGS of a solasfera super ideal cut princess. Some of these do not obtain AGS 0 but wow their appearance destroys many AGS 0 stones http://www.vimeo.com/11694971

 

[ChunkyCushionLover]

Date: 5/12/2010 4:34:49 PM
Author: Todd Gray

Date: 5/12/2010 1:29:16 PM
Author: Stone-cold11
The most you can do is ask for ASET images for the GIA stones.

And the problem with attempting to apply the ASET scope concept to diamonds not graded by the AGS Laboratory is that the view from an ASET scope as seen from the 90 degree view straight down is that it only provides some insight into the optical symmetry of the diamond at that one specific vantage point - at which point, you might as well just look at the Ideal Scope image because the depth of the imagery is about the same - a single static view of the diamond as seen from a 90 degree angle. However the intent behind the ASET scope is entirely different than the purpose of the Ideal Scope... The Ideal Scope was developed to assist people with determining the optical symmetry of the diamond and to determine to what extent the diamond might be leaking light; the ASET scope was developed to judge the potential brightness of the diamond and it is used by the AGSL in conjunction with in-depth mathematical ray tracing (actual reverse ray tracing) which judges the results from more than 200 vantage points or degrees of tilt. Thus using an ASET to look at a GIA graded diamond in an attempt to determine whether it might be comparable to another diamond deemed to be AGS Ideal 0 by the AGS for Light Performance, Polish, Symmetry and Proportions is like saying 'uh, yea, that's a car' but without really having any in-depth idea about the potential the car has in terms of performance.

The only people who can wield the AGS ASET Scope with any degree of accuracy, are the people at the AGS Laboratory because only they are capable of conducting the full ray tracing analysis using the ASET platform; and the results can only be found on the AGS Platinum Diamond Quality Document; anybody else attempting to draw a correlation between a diamond as seen through an ASET scope and the Light Performance grade developed by the AGS Laboratory is essentially defrauding the consumer by way of misrepresentation!

Todd,

Do you feel it is necessary to lead novices into thinking only the AGS can use and interpret their ASET and PGS and not consumers, retailors, and vendors?

Take a look at any .gem file created from a sarin scan of any Infinifty Princess cut and view it under Black ASET30 lighting like the image captures shown below. Over the entire 30 degree range of tilting the diamond gathers light from just about the same angular range in almost every tilt position. In very simple terms the red areas stay red over the entire tilt range with very small differences from the "worst" tilted position over the range to faceup. This seems intuitive to me given the size of the table.

Now it is true the AGS ASET camera has the functionality and was intended as a video camera not just for screen captures but for a full video while a diamond is in movement but it seems quite useful even if a quick and easy faceup image is all that is provided.

It is not just the Infinity Princess where this can be observed their are other branded Princess cuts which gather light from 45 -70 degrees (more red in the ASET) over a larger area of the crown and this predominates over the entire tilt range shown in gemadvisor files as well.

This is the same for a Solasfera and the GOG Signature Princess cuts both of which feature more edge to edge zones of red than the Infinity brand over this entire tilt range.

In this case and others the faceup ASET is quite sufficient for extrapolating and comparing the properties of brightness and contrast especially upon comparing .gem files taken from helium or sarin scans.
I find it hard to beleive that a graphical representation (like ASET image) versus gathering the same information by counting pixels or integrating over an area (like the PGS software) has such a disconnect.

For clarification you can download the Infinity princess I looked at from this link and also download the Solasfera and Gog Signature .gem files from the links above.

Regards,
CCl

 

[ChunkyCushionLover]

Attached Image.

 

[Todd Gray]

Oh where to begin… I suppose that it is only appropriate to begin by thanking you for driving the nails into the coffin CCL, because your posts are a classic example of the very abuse and misinterpretation which I am suggesting needs to be avoided here on Price Scope!

Unless I am misinterpreting the intent of your statements and the examples which you use, you are making the mistake of using simulated images which are generated from scans taken using two different machines… for diamonds of two different facet structures… and trying to determine minutia. Apples and Oranges are both types of round fruit, but they are entirely different in all other ways, the only similarity between a princess cut and a solasfera cut is that both are square cut diamonds.

All the AGSL is attempting to do is separate diamonds into broad cut grades, but what you’re doing is using one 2D snapshot of completely different kinds of stones to extrapolate aspects that the AGSL will tell you cannot yet be extrapolated from that category of data-set; I know this for a FACT because I sat next to AGS Lab Director, Peter Yantzer for three days at the Dallas Symposium which I attended last month and discussed this matter with him in great detail after having had the pleasure of watching his presentation on this very subject.

I suppose that all of that could be considered by some to be irrelevant, yet I believe that the entire premise of your comparison is incorrect to begin with. I have great respect for Rhino, both as a friend and a competitor, and I understand that Rhino used the AGS PGS for his solasfera using the princess setting in an attempt to provide additional insight for his clients, however since the AGSL does not yet have a metric for the solasfera, the bottom line is that the results are inaccurate because they are based on a facet structure of a different configuration. Period. Once again, the only similarity between a princess cut diamond and the solasfera square cut diamond is that they are both square.

Attempting a head to head judgment for an 81-facet stone versus a 45-facet stone using these tools is not a practical comparison, in my opinion since the results will clearly be different based upon the distinct differences of diamond design. I’m not even sure that attempting to make such a comparison would be considered to be ethical by consumers if such as feat was attempted by a member of the trade (?) but I suppose that if the AGSL intended for their software to be used to evaluate the solasfera, that they would have built a custom metric for it to be measured by, however the fact of the matter is that they have not. And I know for a fact that Peter Yantzer and his team possess both the capability and the talent to create the metrics for doing so, they create custom facet structures for the plotting diagrams on lab reports for specialty cut diamonds all the time. It is a fascinating process. However I can’t figure out why the AGSL would be inclined to create such a metric for the solasfera since they seem to be primarily graded by the GIA; which I suppose means that the AGS PGS will never provide a sufficient metric for measuring the solasfera.

As implied by the graphic of the automobile silhouette which I provided as an example above, little can be determined about the potential for brightness between two diamonds for which the only similarity is that they are both square. The implications of angular spectrum are different for different configurations of facet structure and cut precision; period. For those who might not be aware, the AGSL uses separate metrics for configurations which I consider to be closer in similarity than the princess and solasfera, such as for round and oval cut diamonds and that is with a full ray-tracing suite (!) not just a few computer-generated snapshots taken from different scans on different machines… And you have 49 crown facets on the one stone! That is simply a scanner nightmare. Yeah I know that the helium is a great scanner and all, but sorry… I have too much experience to trust 3D scan data for stones with that many subdivided break facets… Been there and done that, it’s not happening.

Even if for a moment, I could convince myself to pretend that the comparison you have suggested is valid; which I can’t; you chose a single data set with a black background. Why would you do that? The white ASET background is much more useful for evaluating leakage versus contrast; especially for fancy shape diamonds. A professional diamond buyer would know this, a consumer probably wouldn’t and here again is my issue with “pro-sumers” running all over the forum telling less knowledgeable consumers “get an ASET; get an ASET” because purchasing decisions are being made on limited results and inaccurate assumptions. I realize that this is likely not to be a popular opinion amongst the pro-sumers on the forum, I thought about that before raising the issue to this height; however I believe that the continued assumption that a static view of a diamond as seen through an ASET scope is an extreme disservice to the very consumers who come to this forum seeking true insight.

Since we’re all here to learn and this includes me… Take a look at the PGS simulation of the solasfera, with white background, and you’ll notice a lack of red at the edges, whereas the ASET of the Infinity Diamond on HPD, which is an actual photo by the way and not a computer generated scan; shows red at the long outer edges, even in the more-challenging white-backed metric... This alone contradicts your basic conclusions… However since as I stated above, attempting to compare results for a square solasfera and a princess cut diamond is far from an apples to apples comparison, I am not drawing any conclusion other than the basis for your conclusion is without foundation. We could argue that the solasfera scan might be a little wonky; that the standardization of our photo may vary from the simulation; that the angular spectrum which I have come to expect may not be appropriate for its configuration, blah, blah, blah… But this is a text book example of why I said what I said earlier in this thread and warned of the potential for abuse of the AGS PGS software, naturally I did not have my friend Rhino in mind when I made that statement; I was not aware that he was attempting to use the software to evaluate solasfera cut diamonds and imagine that he is doing so for comparative purposes of solasfera to solasfera cut diamonds only because as stated, it would be absurd to attempt to use the software to draw a comparison between a square solasfera and a princess cut diamond since the metrics would have to be entirely different for the differences stated above.

This is an opportunity for us to learn that a lot of different looks exist and we can “snap” any one of them in an attempt to support whatever argument we want to make: - 30blue; 40blue; 30blue/white; 40blue/white; all of the forward and reverse ray-tracing views as well; as yet-unincorporated views for small, medium, large and cosine20 scintillation events. All of this and we have not even discussed the other reflector topics which I could raise to further make this point. All of these possibilities when considered together tell a story; and it’s a useful one. However even that story, as seen by the AGSL, is only used for placing diamonds which it has had the opportunity to grade and scan using the equipment which the AGS PGS was designed specifically to be used with, is only for placing a diamond inside a broad cut grade, not to attempt to dissect minutia like you are attempting to do.

I believe that I understand the intent of your argument, but to be it in local terms, that dog won’t hunt... And I think that there are a lot of people who have spent a lot of time researching diamonds and believe that they are capable of making minor distinctions about diamonds from minute details as provided by images being evaluated on their computer monitor at an average quality of 72 dots per inch. But I’ve been in the business of buying diamonds since 1985 and I have seen thousands and thousands of diamonds cross my desk. And that is the point really… There is no substitute for the experience of seeing thousands of diamonds and having the opportunity of comparing what I see with the scans created by the equipment available to us. The same premise holds true for attempting to determine the extent and visibility, color, tone, etc. for a clarity image as viewed from a computer monitor as compared to actually being able to examine the inclusions as seen through a gem scope using various degrees of magnification and soapy water. Any gemologist experienced with these things will verify that what I am saying is true.

Author Mark Twayne once said “Lies, damned lies, and statistics” to describe the persuasive power of numbers, particularly the use of statistics to bolster weak arguments and the tendency of people to disparage statistics that do not support their position. “Lies, damned lies and statistics” seems like a statement that could easily be applied to the use of unauthorized, inaccurate and inappropriate use of the AGS PGS to attempt to designate a light performance rating for diamonds not graded by the AGSL and for which the AGS obviously never intended their software to be used… But we’d have to change it to “Lies, damned lies and computer generated images”.

But to address the real question at hand CCL… No, I am not trying to lead novices into thinking anything other than the fact that this subject is quite complex. Are you?

 

[Todd Gray]

I forgot to attach the picture

 

[Karl_K]

Date: 5/19/2010 3:14:45 PM
Author: Todd Gray
Unless I am misinterpreting the intent of your statements and the examples which you use, you are making the mistake of using simulated images which are generated from scans taken using two different machines… for diamonds of two different facet structures… and trying to determine minutia.

You just shot yourself in the foot right there, that is exactly what AGS does.
I am getting rather annoyed with AGS dealers pushing AGS as the ultimate.
Is it pretty good, yes, perfect, far from it.
Garbage in/garbage out is the biggest flaw.
Over simplified is another.

As far as the AGS software it is the official position of AGS that the AGS software can give a diamond the AGS light performance grade.

If you want to argue that only AGS can determine if a diamond is well cut then there is a real problem.

 

[Karl_K]

Date: 5/19/2010 3:14:45 PM
Author: Todd Gray
But we’d have to change it to “Lies, damned lies and computer generated images”.

That is the same thing as saying damned lies and scan based cut grades.

What is funny is a huge chunk of the AGS cut grade is based on computer generated images.

 

[Karl_K]

Date: 5/12/2010 4:34:49 PM
Author: Todd Gray

The only people who can wield the AGS ASET Scope with any degree of accuracy, are the people at the AGS Laboratory because only they are capable of conducting the full ray tracing analysis using the ASET platform; and the results can only be found on the AGS Platinum Diamond Quality Document; anybody else attempting to draw a correlation between a diamond as seen through an ASET scope and the Light Performance grade developed by the AGS Laboratory is essentially defrauding the consumer by way of misrepresentation!

Now that I can agree with somewhat, AGS''s opinion on a diamond should be their actual opinion. There are 2 AGS approved ways of doing that and that is the grading report and the software. To do otherwise is misrepresentation.

On the other hand using ASET images by itself does not imply that AGS has given an opinion on a diamond.
They are actually using the AGS scope for what AGS intended, to show a client images of a diamond as a sales tool.
So I strongly disagree that only AGS can properly use an ASET, they don''t use one anyway it is a scan based grade.

 

[Karl_K]

Date: 5/19/2010 12:08:33 AM
Author: ChunkyCushionLover
Attached Image.

You have to be careful with scan based images they are not always true.
The same caution applies to scan based cut grades so it is nice to see actual images and the opinion of someone skilled in the art of high performance diamonds is still important.

Keep on challenging the trade including me, but listen and learn when it makes sense to :}
Your not always right but it is a good thing.
I made it my practice to do so for years and it not only benefited me as I stepped up my game but those I debated with in making them step up their game to match.

 

[ChunkyCushionLover]

Date: 5/19/2010 3:34:51 PM
Author: Todd Gray
I forgot to attach the picture

My comparison was based on simulated images both using Black ASET to show how the tilted positions don''t differ much from the faceup.
You could perform the same excercise photographing through an ASET scope on an infinity princess over the same tilt range if you wish you will arrive at the same result.

I used the standardized lighting and tilt position provided by the gemadvisor files for equality purposes not that they are the highest quality images due to scan error.

There is a difference between the two images it has to do with background color, photography setup and scanning error. Not negligible but not something to be overly worried about in most cases.

I purposely did not compare photographed images because I don''t have tilted photographed images to show but those could easily be taken by both vendors.
This image should show definitively there is very little difference between the photographed and simulated images for both diamonds. Not enough that It would change my mind if I was comparing the two.

 

[ChunkyCushionLover]

Not necessary to worry about the scan error in this comparison both are close. This also doesn't change the fact that the tilted images mare not differeing much from faceup over the useful viewing range.
Please do provide Actual Cut Diamond examples of princess cuts that have false positive or negative results from faceup ASET if you have any Todd or Karl. I am also not worried about the different hue or intensity of the reds either those differences may result from lighting conditions and not the actual diamond. In addition the difference in due to scanning error is even less than the differences in comparing white background to black background ASET but that could be fixed in new white background lighting for the .gem files.

 

[diagem]

Date: 5/19/2010 5:17:28 PM
Author: ChunkyCushionLover

Date: 5/19/2010 3:34:51 PM
Author: Todd Gray
I forgot to attach the picture

My comparison was based on simulated images both using Black ASET to show how the tilted positions don''t differ much from the faceup.
You could perform the same excercise photographing through an ASET scope on an infinity princess over the same tilt range if you wish you will arrive at the same result.

I used the standardized lighting and tilt position provided by the gemadvisor files for equality purposes not that they are the highest quality images due to scan error.

There is a difference between the two images it has to do with background color, photography setup and scanning error. Not negligible but not something to be overly worried about in most cases.

I purposely did not compare photographed images because I don''t have tilted photographed images to show but those could easily be taken by both vendors.
This image should show definitively there is very little difference between the photographed and simulated images for both diamonds. Not enough that It would change my mind if I was comparing the two.

CCL, from my experience in comparing computer generated Asets & real photography Asets, some are indeed strikingly close in resemblance, but some models are completely off.
I am just expressing this as a fact..., not specifically on the subject of this thread.

I notice a clear difference in the (Solasfera) example you added above..., the real McCoy looks much better than the generated one.

 

[Karl_K]

Date: 5/19/2010 5:21:05 PM
Author: ChunkyCushionLover
Not necessary to worry about the scan error in this comparison both are close. This also doesn't change the fact that the tilted images mare not differeing much from faceup over the useful viewing range.

Please do provide Actual Cut Diamond examples of princess cuts that have false positive or negative results from faceup ASET if you have any Todd or Karl.

I do and can quickly find many more, but I wont post the ASET it does not accurately represent the diamond and it could be identified but it does look close face up to the actual diamond ASET image.
As the virtual image is tilted these scan errors build on each other and it diverges even further from real.
This image is the scan data the ASET image would be based on, are you willing to base a decision on it?
I am not.
Scan based images much be approached with caution.
Some are ok but many are not.

 

[ChunkyCushionLover]

Date: 5/19/2010 5:36:03 PM
Author: DiaGem

Date: 5/19/2010 5:17:28 PM
Author: ChunkyCushionLover

Date: 5/19/2010 3:34:51 PM
Author: Todd Gray
I forgot to attach the picture

My comparison was based on simulated images both using Black ASET to show how the tilted positions don''t differ much from the faceup.
You could perform the same excercise photographing through an ASET scope on an infinity princess over the same tilt range if you wish you will arrive at the same result.

I used the standardized lighting and tilt position provided by the gemadvisor files for equality purposes not that they are the highest quality images due to scan error.

There is a difference between the two images it has to do with background color, photography setup and scanning error. Not negligible but not something to be overly worried about in most cases.

I purposely did not compare photographed images because I don''t have tilted photographed images to show but those could easily be taken by both vendors.
This image should show definitively there is very little difference between the photographed and simulated images for both diamonds. Not enough that It would change my mind if I was comparing the two.

CCL, from my experience in comparing computer generated Asets & real photography Asets, some are indeed strikingly close in resemblance, but some models are completely off.
I am just expressing this as a fact..., not specifically on the subject of this thread.

I notice a clear difference in the (Solasfera) example you added above..., the real McCoy looks much better than the generated one.

Yes indeed. If you were judging optical symmetry or the amount of obstruction the scanning error on the Solasfera makes it look a little worse.
The ASET30 is a little strange sometimes you get areas with obstruction that change very quickly to gathering light from 45-70 degrees and in the simulations instead of blue or red its a mix which is purple.

I''m not sure what you mean by models, some scans can be way off, but you are saying some Diamcalc or AGS models are off? For which cuts?
Sarin has gotten better, helium is even better, new software is being released and the scanning error is only being reduced.

I don''t think it hurts a comparative decision if the diamond looks a little worse than IRL if you are comparing both using the same simulated method.

 

[diagem]

Date: 5/19/2010 7:20:28 PM
Author: ChunkyCushionLover

Date: 5/19/2010 5:36:03 PM
Author: DiaGem

Date: 5/19/2010 5:17:28 PM
Author: ChunkyCushionLover

Date: 5/19/2010 3:34:51 PM
Author: Todd Gray
I forgot to attach the picture

My comparison was based on simulated images both using Black ASET to show how the tilted positions don''t differ much from the faceup.
You could perform the same excercise photographing through an ASET scope on an infinity princess over the same tilt range if you wish you will arrive at the same result.

I used the standardized lighting and tilt position provided by the gemadvisor files for equality purposes not that they are the highest quality images due to scan error.

There is a difference between the two images it has to do with background color, photography setup and scanning error. Not negligible but not something to be overly worried about in most cases.

I purposely did not compare photographed images because I don''t have tilted photographed images to show but those could easily be taken by both vendors.
This image should show definitively there is very little difference between the photographed and simulated images for both diamonds. Not enough that It would change my mind if I was comparing the two.

CCL, from my experience in comparing computer generated Asets & real photography Asets, some are indeed strikingly close in resemblance, but some models are completely off.
I am just expressing this as a fact..., not specifically on the subject of this thread.

I notice a clear difference in the (Solasfera) example you added above..., the real McCoy looks much better than the generated one.

Yes indeed. If you were judging optical symmetry or the amount of obstruction the scanning error on the Solasfera makes it look a little worse.
The ASET30 is a little strange sometimes you get areas with obstruction that change very quickly to gathering light from 45-70 degrees and in the simulations instead of blue or red its a mix which is purple.

Yes..., I believe its a symptom of facet/LR sensitivity...,

I''m not sure what you mean by models, some scans can be way off, but you are saying some Diamcalc or AGS models are off? For which cuts?
Sarin has gotten better, helium is even better, new software is being released and the scanning error is only being reduced.
Both..., when comparing between AGS & DC..., I believe AGS admitted to this problem.
I don''t think it hurts a comparative decision if the diamond looks a little worse than IRL if you are comparing both using the same simulated method.

 

[ChunkyCushionLover]

Date: 5/19/2010 5:54:49 PM
Author: Karl_K

Date: 5/19/2010 5:21:05 PM
Author: ChunkyCushionLover
Not necessary to worry about the scan error in this comparison both are close. This also doesn't change the fact that the tilted images mare not differeing much from faceup over the useful viewing range.

Please do provide Actual Cut Diamond examples of princess cuts that have false positive or negative results from faceup ASET if you have any Todd or Karl.

I do and can quickly find many more, but I wont post the ASET it does not accurately represent the diamond and it could be identified but it does look close face up to the actual diamond ASET image.
As the virtual image is tilted these scan errors build on each other and it diverges even further from real.
This image is the scan data the ASET image would be based on, are you willing to base a decision on it?
I am not.
Scan based images much be approached with caution.
Some are ok but many are not.

Karl when I wrote Actual Cut Diamond I knew that you could show a simulated theoretical design image or a bad scan.
"Bad Scans" aside do you have any example of either false positive or negative from a faceup photographed ASET image? (eg faceup it looked great, upon tilting not so much or vice versa?)

Do you see some systematic bias (good or bad) in princess cut simulated images based on generated images from sarin or helium data?

You have mentioned several times that the AGS bases the cut grade on potentially bad input of sarin data, however each of the metrics has deduction tolerances especially for fancy shapes do you really beleive it is common for the scanning error to change the light performance grade significantly?

 

[Karl_K]

Date: 5/19/2010 7:38:13 PM
Author: ChunkyCushionLover
Karl when I wrote Actual Cut Diamond I knew that you could show a simulated theoretical design image.

It is a sarin scan based DC wire frame image of a REAL diamond based on the sarin data(gem file).
I can not show the aset images because it is not my diamond and could be identified.
You asked to see scanner error and that is what I showed you.

 

[Karl_K]

Here is another.....
I could keep posting these all night as examples of garbage in...

 

[Karl_K]

this one is much better and the resulting ASET image is very close face up.
But the scan errors will show up more as it is tilted.
Viewing the face up ASET images side by side you would not be able to locate the scan error unless you blew it up full screen.

 

[Todd Gray]

Point missed, I suppose that it''s my fault for writing a small novel, why would I expect anybody to read it?

To be clear Karl, I am not pushing the AGS as the ultimate diamond grading laboratory (although I do prefer it for princess cuts)... I''m saying that it is irresponsible to tell consumers to simply "ask for an ASET" when they post the question "is this a good diamond" etc. because there is very little that anybody can truly tell them about the diamond based on peek of the diamond from a single view. The door was opened regarding the AGS PGS and I cautioned that some dealers might misuse the software and that the results of such action is misleading to consumers.

The point that I''m trying to make regarding the comparison offered by CCL is this:

The scans presented represent diamonds of two different configurations. ASET results aside; issues pertaining to scan quality aside; the reality is that the virtual facets (because of facet distribution) will be absolutely different between these two cuts. ASET red is nice. Bravo. Both stones are bright in many illumination environments. It has nothing to do with the virtual facet pattern which changes everything about the way these diamonds look in real life.

 

[Karl_K]

Todd the main thing is:

An ASET image is a valuable piece of information that is better than not having one.
I 100% support consumers asking for one.
1: it eliminates the worst of the drop shippers.
2: gives some information about the diamond.

Is an ASET the ultimate answer?, no
Is it helpful? Yes.
I never have and never will advocate purchasing a diamond based on one data point and neither would you.
In that context asking for an ASET image is a good thing!

 

[ChunkyCushionLover]

Date: 5/19/2010 3:14:45 PM
Author: Todd Gray
Oh where to begin… I suppose that it is only appropriate to begin by thanking you for driving the nails into the coffin CCL, because your posts are a classic example of the very abuse and misinterpretation which I am suggesting needs to be avoided here on Price Scope!

Todd what I find most disagreeable with this thread is that you are rejecting all comparison tools and leading consumers to only the "proven" branded lines. While I don't generally have a problem with your statements which often promote directly or indirectly Infinity Diamonds (that you happen to sell), I do however feel this thread crosses a line especially since there are so many factual inaccuracies and assumptions (see below) made in your statements.

Unless I am misinterpreting the intent of your statements and the examples which you use, you are making the mistake of using simulated images which are generated from scans taken using two different machines… for diamonds of two different facet structures… and trying to determine minutia. Apples and Oranges are both types of round fruit, but they are entirely different in all other ways, the only similarity between a princess cut and a solasfera cut is that both are square cut diamonds.

The examples chosen were both of well cut and characterized Princess cuts, I am well aware the one has two chevrons (Infinity) while the other has three (Solasfera).
But this is secondary and the examples chosen were only to to show why the faceup is a good overall indicator of the important tilted positions as well.
Do you not see how little difference slight tilting makes to where these two diamonds gather light from? The greatest difference is small areas show contrast(obstruction) which is favoured in some positions over others.
See the .gem video files if you don't accept my captures.

All the AGSL is attempting to do is separate diamonds into broad cut grades, but what you’re doing is using one 2D snapshot of completely different kinds of stones to extrapolate aspects that the AGSL will tell you cannot yet be extrapolated from that category of data-set; I know this for a FACT because I sat next to AGS Lab Director, Peter Yantzer for three days at the Dallas Symposium which I attended last month and discussed this matter with him in great detail after having had the pleasure of watching his presentation on this very subject.

I will invite Peter to this thread I hope you will do the same. Regardless, the AGS research on the correlation between ASET and real world diamond performance published here and elsewhere stands on its own and came before the PGS.

I suppose that all of that could be considered by some to be irrelevant, yet I believe that the entire premise of your comparison is incorrect to begin with. I have great respect for Rhino, both as a friend and a competitor, and I understand that Rhino used the AGS PGS for his solasfera using the princess setting in an attempt to provide additional insight for his clients, however since the AGSL does not yet have a metric for the solasfera, the bottom line is that the results are inaccurate because they are based on a facet structure of a different configuration. Period. Once again, the only similarity between a princess cut diamond and the solasfera square cut diamond is that they are both square.

You have confused so many different things here.

1) Rhino did not produce the Solasfera nor is he their only vendor. Solasfera is a brand name and a supplier in its own capacity.
2) The Solasfera has attained AGS 0 on grading reports already see the DQD for this diamond
3) I have no idea what you mean by the AGSL does not have a metric for the Solasfera?

Attempting a head to head judgment for an 81-facet stone versus a 45-facet stone using these tools is not a practical comparison, in my opinion since the results will clearly be different based upon the distinct differences of diamond design. I’m not even sure that attempting to make such a comparison would be considered to be ethical by consumers if such as feat was attempted by a member of the trade (?) but I suppose that if the AGSL intended for their software to be used to evaluate the solasfera, that they would have built a custom metric for it to be measured by, however the fact of the matter is that they have not. And I know for a fact that Peter Yantzer and his team possess both the capability and the talent to create the metrics for doing so, they create custom facet structures for the plotting diagrams on lab reports for specialty cut diamonds all the time. It is a fascinating process. However I can’t figure out why the AGSL would be inclined to create such a metric for the solasfera since they seem to be primarily graded by the GIA; which I suppose means that the AGS PGS will never provide a sufficient metric for measuring the solasfera.

The number of facets is a personal preference much like LGF length in rounds and is a subjective beauty aspect not a light performance metric to be graded.
There are 8 more facets on the pavillion of an 3 chevron versus a 2 chevron princess but since the Infinity has 4 more crown facets the difference is only 4 facets! How did you come up with those numbers?
Please do not confuse how they generate new templates for their inclusion plot diagrams ( Sarin > Gemcad > Fit To Sarin Data >Plot) and the PGS software whose metrics do not change based on a new pavillion facet structure.

The AGS does grade princess cuts with different pavillion facet structures using the same light performance criteria. I would shutter to think what kind of credibility they would have if they bent their performance grading to suit new cuts or suppliers.


As implied by the graphic of the automobile silhouette which I provided as an example above, little can be determined about the potential for brightness between two diamonds for which the only similarity is that they are both square. The implications of angular spectrum are different for different configurations of facet structure and cut precision; period. For those who might not be aware, the AGSL uses separate metrics for configurations which I consider to be closer in similarity than the princess and solasfera, such as for round and oval cut diamonds and that is with a full ray-tracing suite (!) not just a few computer-generated snapshots taken from different scans on different machines… And you have 49 crown facets on the one stone! That is simply a scanner nightmare. Yeah I know that the helium is a great scanner and all, but sorry… I have too much experience to trust 3D scan data for stones with that many subdivided break facets… Been there and done that, it’s not happening.

Even if for a moment, I could convince myself to pretend that the comparison you have suggested is valid; which I can’t; you chose a single data set with a black background. Why would you do that? The white ASET background is much more useful for evaluating leakage versus contrast; especially for fancy shape diamonds. A professional diamond buyer would know this, a consumer probably wouldn’t and here again is my issue with “pro-sumers” running all over the forum telling less knowledgeable consumers “get an ASET; get an ASET” because purchasing decisions are being made on limited results and inaccurate assumptions. I realize that this is likely not to be a popular opinion amongst the pro-sumers on the forum, I thought about that before raising the issue to this height; however I believe that the continued assumption that a static view of a diamond as seen through an ASET scope is an extreme disservice to the very consumers who come to this forum seeking true insight.

The images above was meant to show one thing, tilt the diamond 15 degrees in either direction or anything less versus faceup the images are quite similar. You are right your opinion is not popular and you haven't supported it by showing us false positives or examples of misrepresentation by other vendors. If anything poorly scanned sarin results and simulated images make stones look worse not better and it is in the vendor's best interests to redo the scans if they feel this has occurred.

Since we’re all here to learn and this includes me… Take a look at the PGS simulation of the solasfera, with white background, and you’ll notice a lack of red at the edges, whereas the ASET of the Infinity Diamond on HPD, which is an actual photo by the way and not a computer generated scan;

Integrate the areas of the red regions of the two diamonds it is not even close the Solasfera has much more red.
Once again I don't want to get into a comparison of the two but there are some videos on Vimeo and youtube of Solasfera versus other AGS 0 princess cuts if you are interested.


shows red at the long outer edges, even in the more-challenging white-backed metric... This alone contradicts your basic conclusions… However since as I stated above, attempting to compare results for a square solasfera and a princess cut diamond is far from an apples to apples comparison, I am not drawing any conclusion other than the basis for your conclusion is without foundation. We could argue that the solasfera scan might be a little wonky; that the standardization of our photo may vary from the simulation; that the angular spectrum which I have come to expect may not be appropriate for its configuration, blah, blah, blah… But this is a text book example of why I said what I said earlier in this thread and warned of the potential for abuse of the AGS PGS software, naturally I did not have my friend Rhino in mind when I made that statement; I was not aware that he was attempting to use the software to evaluate solasfera cut diamonds and imagine that he is doing so for comparative purposes of solasfera to solasfera cut diamonds only because as stated, it would be absurd to attempt to use the software to draw a comparison between a square solasfera and a princess cut diamond since the metrics would have to be entirely different for the differences stated above.

This is an opportunity for us to learn that a lot of different looks exist and we can “snap” any one of them in an attempt to support whatever argument we want to make: - 30blue; 40blue; 30blue/white; 40blue/white; all of the forward and reverse ray-tracing views as well; as yet-unincorporated views for small, medium, large and cosine20 scintillation events. All of this and we have not even discussed the other reflector topics which I could raise to further make this point. All of these possibilities when considered together tell a story; and it’s a useful one. However even that story, as seen by the AGSL, is only used for placing diamonds which it has had the opportunity to grade and scan using the equipment which the AGS PGS was designed specifically to be used with, is only for placing a diamond inside a broad cut grade, not to attempt to dissect minutia like you are attempting to do.

Todd I pointed you to the .gem files, I have accurately snapped the images with the most obstruction in them and therefore the "worst" position over the 30 degree tilt range. If you disagree just view the whole video of each and choose your own snapshot.

ASET 30 is a cone with 75 - 90 degrees and 90 - 105 degrees being considered blocked by the viewers head and obstructed (ASET Blue). This is the same cone of obstruction as in the white background ASET scopes where the images were taken.

It would be more misleading to choose ASET 40 as then a comparison with the photographed images would not be equivalent.

I believe that I understand the intent of your argument, but to be it in local terms, that dog won’t hunt... And I think that there are a lot of people who have spent a lot of time researching diamonds and believe that they are capable of making minor distinctions about diamonds from minute details as provided by images being evaluated on their computer monitor at an average quality of 72 dots per inch. But I’ve been in the business of buying diamonds since 1985 and I have seen thousands and thousands of diamonds cross my desk. And that is the point really… There is no substitute for the experience of seeing thousands of diamonds and having the opportunity of comparing what I see with the scans created by the equipment available to us. The same premise holds true for attempting to determine the extent and visibility, color, tone, etc. for a clarity image as viewed from a computer monitor as compared to actually being able to examine the inclusions as seen through a gem scope using various degrees of magnification and soapy water. Any gemologist experienced with these things will verify that what I am saying is true.

Author Mark Twayne once said “Lies, damned lies, and statistics” to describe the persuasive power of numbers, particularly the use of statistics to bolster weak arguments and the tendency of people to disparage statistics that do not support their position. “Lies, damned lies and statistics” seems like a statement that could easily be applied to the use of unauthorized, inaccurate and inappropriate use of the AGS PGS to attempt to designate a light performance rating for diamonds not graded by the AGSL and for which the AGS obviously never intended their software to be used… But we’d have to change it to “Lies, damned lies and computer generated images”.

But to address the real question at hand CCL… No, I am not trying to lead novices into thinking anything other than the fact that this subject is quite complex. Are you?

Todd,

Please invite Peter Yantzer here I will do the same.

To enter a proper discussion and a proper educational thread you need to explain alll the light performance metrics for the PGS software, which tilt positions are considered and what the weightings for each tilt position.
While some of this information on how each of these metrics are calculated and positions can found here the formulas for weighting are not. You have already created confusion on this when you said Dispersion is not being considered I beleive this to be false.

Rather than argue over my examples lets take a closer look at how the PGS calculates the performance cut grade. Anything to share like slides perhaps from the symposium?