An AGS view of GIA Steep Deep Excellent

[Regular Guy]

Garry,

I do appreciate both your genuine/critical and also, mature approach to reviewing this data. But, where you say:

Date: 8/31/2005 4:52:15 PM
Author: Garry H (Cut Nut)

Imagine the confusion for retailers and shoppers when GIA and AGS give the same diamond very different Cut grades?

This will be the case after the first of January 2006. There will be many diamonds graded GIA Excellent that will receive only Good grades from (AGS 2, 3, 4 & 5). There will also be AGS 0 or Ideal grade diamonds that will only receive GIA Good & Very Good grades.

And we are supposed to be the independant authorities in this field. It is going to be a big problem.

I haven''t frequently heard the supposition that AGS zeros would be considered only good & very good by GIA...and I think people both have and can understand the "conical" approach to standards and hierarchy...that AGS may have a higher/stricter standard for excellence, such that, although virtually all GIA excellents would be regarded as also excellent by AGS, the reverse would not be true. This is logic that is understandable, and is typically considered to be the case right now, as well, described here often enough.

Based on known even theoretical examples, are there some sets of proportions, for example, where you think an AGS0 would only go good or very good with GIA?

Regards,

 

[Garry H (Cut Nut)]

Date: 8/31/2005 4:52:15 PM
Author: Garry H (Cut Nut)

Imagine the confusion for retailers and shoppers when GIA and AGS give the same diamond very different Cut grades?

This will be the case after the first of January 2006. There will be many diamonds graded GIA Excellent that will receive only Good grades from (AGS 2, 3, 4 & 5). There will also be AGS 0 or Ideal grade diamonds that will only receive GIA Good & Very Good grades.

And we are supposed to be the independant authorities in this field. It is going to be a big problem.

Ira > Garry I haven't frequently heard the supposition that AGS zeros would be considered only good & very good by GIA...and I think people both have and can understand the "conical" approach to standards and hierarchy...that AGS may have a higher/stricter standard for excellence, such that, although virtually all GIA excellents would be regarded as also excellent by AGS, the reverse would not be true. This is logic that is understandable, and is typically considered to be the case right now, as well, described here often enough.

Based on known even theoretical examples, are there some sets of proportions, for example, where you think an AGS0 would only go good or very good with GIA?

Regards,

Ira Z.

Ira all the AGS 0 stones with tables between 50 and 47% will be GIA Goods and a few might be Very Good.

There are many examples from AGS's chart of 'candidates' that - like the one shown here that get lower grades on the GIA's facetware http://facetware.gia.edu/ HCA type web site.

 

[strmrdr]

Date: 8/31/2005 6:06:08 AM
Author: Garry H (Cut Nut)
Here is the picture I used to make these assumptions

Garry, Im confused by your comments on this picture.
The picture does not match what they said they used for the observation testing.
In the text they said domes were used.
Further they said the main domes used had openings for just one eye to look in.
Am I missing something?

 

[Garry H (Cut Nut)]

From the gIA website: http://www.gia.edu/research/29324/diamond_cut_faq.cfm#observations1
How was the observer-diamond geometry determined for the observation tests and modeling used to develop the GIA Diamond Cut Grading System? In your modeling, do you account for the rocking and tilting of diamonds during observation?

In the initial stages of our observation research, we visited a number of experienced diamond manufacturers, brokers, and retailers, and measured physical relationships in the environments they used to observe diamonds. These measurements included ranges of diamond-to-light-source and diamond-to-observer distances, ranges of viewing angles (tilts), and types of illumination and their intensities.

The common viewing environment we developed and used, and the method for observing diamonds in this environment, define the most important common elements of these observer/observation factors that we found to be critical to consistent and reliable observations of diamond appearance. For example, we used our findings on observer-diamond distance to determine the viewing range that provided the most consistent results.



I think that means the lighting position was set up as that used in a wholesale diamond buying / selling office.
That can explain the way they designed the CVE - which I think is wrong from a consumers view point. Wholesale and retail selling environments are a hot topic here on Pricscope - there are many threads where consumers discuss these issues. try here

We have discussed the idea many times here that blasting a diamond with very bright light will make diamonds appear more sparkly than they will in normal every day lighting. So lets ask some questions?

1. The intensity of light when there are 2 fluoro tubes about 18 inches (45cm) from the diamond is the equivalent of 16 tubes in the ceilng 6 foot (1.8m) higher. (Is my math correct?)

2. To view fire GIA added enough LED''s to make it possible to see fire with the fluoro''s turned on. I would make a stab in the dark that might be the equivalent of 1 or 2 dozen halogen spot lights in your living room (the one with 16 fluoro tubes

)

(Quote from the above website "Intensities of the two light sources were established by determining when a set of reference diamonds showed the same relative amounts of brightness and fire respectively as they showed in the dealer- and retail-equivalent lighting conditions we described in the article. In this way we were able to combine the observable appearance aspects of brightness and fire in a single viewing environment, while also preserving the general qualities of both dealer and retail lighting."
And this one: "Do your metrics and observer viewing conditions incorporate aspects of both trade and consumer environments?
Consumer environments can vary quite a bit, as consumers typically buy their diamond jewelry in a store, and then wear it in nearly every environment. While diffuse lighting is often typical for most offices, there are a variety of mixed lighting environments that consumers work and live in. Although we felt it was important to develop a viewing environment that was consistent with the places in which consumers would view their jewelry, we believed it was critical that the environment be logical for those who regularly make essential diamond manufacturing and purchasing decisions.")

3. Has anyone seen the lighting inside the CVE? Please do tell.

4. The darkness around the CVE:

"The dark area in the GIA brightness metric is 23 degrees in radius; this seems too large for a “head shadow.” Doesn’t this make many diamonds appear dark?
The (top) dark area for our brightness metric is 23 degrees in radius, centered at the dome zenith; however, it does not represent a “head shadow.” Observations through hemispheres that re-created the metric environment were used to establish relative rank order for the appearance of brightness, not to match patterns observed in more typical lighting. The rank order for brightness determined from metric calculations using this environment was the best match to that determined by observers in our common viewing environment."
Hmmmm, that suggests to me that the light in the CVE is so intense, that even with normal lighing behind the observer, the background would be quite dark from the observers perspective - hence the shadows and darkness we can see in the areas around the CVE. The observers would typically have found the lower table area closest to them to be dark in most all stones - but this would go brighter as they rocked the stones - which because of the tray proportions - most rocking would have been toward and away - not left to right. Therefore the leakiest stones under such intense bright lighting would have been brighter in the leakage zone than stomnes that did not leak. This might also explain why they would reject the stone RD 16 which has lower girdle facets that are too short and a slightly shallow pavilion - i.e. it has very little leakage, a lot of head obstruction, but would probably display a lot of fire in more realistic lighting.


GIA mentions this Lighting box as an all industry standard that GIA seems to have based its CVE on:
http://usa.gretagmacbethstore.com/index.cfm/act/Catalog.cfm/catalogid/2110/Subcategory/Controlled%20Lighting%20Systems/category/Controlled%20Lighting/browse/null/MenuGroup/Menu%20USA%20New/desc/Judge%20II%20Portable%20Viewing%20Booth.htm

Finally anyone who is good at it - please try to find the patent application fro the CVE

 

[strmrdr]

Reads to me like 2 environments were used both domes and the one shown.
At this point does anyone actually know for a fact what they did?
It seems like they are releasing bits and pieces and not enough data to come to very many conclusions.
But speculating is fun :}

 

[Garry H (Cut Nut)]

Date: 9/1/2005 4:34:35 AM
Author: strmrdr

Date: 8/31/2005 6:06:08 AM
Author: Garry H (Cut Nut)
Here is the picture I used to make these assumptions

Garry, Im confused by your comments on this picture.
The picture does not match what they said they used for the observation testing.
In the text they said domes were used.
Further they said the main domes used had openings for just one eye to look in.
Am I missing something?

Sorry Storm, missed that one.

I think the domes were part of an attempt to match observation to the Virtual computer modelling. I get the feeling they tried to make it look like they used the computer system so they would not be seen to be wasting the $$$ spent on it.

The real basis appears to be from observation tests in the CVE - the plastic salad bowls were left over from long lunches.

The light return computer modelling from 1998 showed that steep deep stones had lousy light return, and the best fire range was one that you guys would all approve of.

 

[strmrdr]

Date: 9/1/2005 7:42:32 AM
Author: Garry H (Cut Nut)

Date: 9/1/2005 4:34:35 AM

The real basis appears to be from observation tests in the CVE - the plastic salad bowls were left over from long lunches.

Could you explain why you feel that way?
Im not saying your wrong at this point but im curious at what brought you to that conclusion?

 

[Regular Guy]

Date: 8/31/2005 5:56:46 PM
Author: Garry H (Cut Nut)

Ira all the AGS 0 stones with tables between 50 and 47% will be GIA Goods and a few might be Very Good.

There are many examples from AGS''s chart of ''candidates'' that - like the one shown here that get lower grades on the GIA''s facetware http://facetware.gia.edu/ HCA type web site.

Though the concern about confusion may be not only reasonable and logical, as well as consistent with your system of 3 types of ideals, including the FIC as a type that makes up, by your claim, one in 2000 identified, I find now that in the available set of 1156 round diamonds on the search by cut database, the smallest table is at 53 today, and have to wonder if the anticipated occurence of these possibly AGS0 stones that would also rank as GIA sub-excellent might not be very small, such that one might hardly worry, to speak of.

Then again, with my wife''s FIC in hand, maybe...what is that saying...I am calling the kettle black.

Regards,

 

[oldminer]

Garry and all;

I did do the GIA test in the light boxes. I thought the lights were bright enough to clearly see performance. The room was rather dimly lit otherwise. It was a good environment for looking at those stones. The ones that ranked high were bound to look good in nearly any reasonable regular lighting. At least, that''s what I would hold as an opinion. I was not able to view them in my own lighting environment or in regular room lighting. I just assume the ligting was good enough to bring out the looks of better stones and to let observers see that lesser stones looked less sparkly and bright.
It was a reasonably controlled environment, but not totally controlled. We could move the diamonds around and hold them at most any distance from our eyes.

The entire industry is going to have issues and problems with the situation of AGS and GIA grading differently. ImaGem will likely be more like AGS, but again, the results may be a little different, too. It is now a battle as to which becomes accpeted standards. Possibly all, maybe only one. It is going to be confusing and problematic, especially for cutters.

 

[Garry H (Cut Nut)]

Date: 9/1/2005 8:16:46 AM
Author: strmrdr

Date: 9/1/2005 7:42:32 AM
Author: Garry H (Cut Nut)

Date: 9/1/2005 4:34:35 AM

The real basis appears to be from observation tests in the CVE - the plastic salad bowls were left over from long lunches.

Could you explain why you feel that way?
Im not saying your wrong at this point but im curious at what brought you to that conclusion?

1 The real basis appears to be from observation tests in the CVE this is part personal events and part things said at GIA presentations that match with what I read - but it is an 80% hunch - there is not enough evidence either way.

2. the plastic salad bowls they were part of an experiment in establishing the ground rules for the CVE as i understood it

3. long lunches I am jelous

 

[Garry H (Cut Nut)]

Date: 9/1/2005 9:14:11 AM
Author: Regular Guy

Date: 8/31/2005 5:56:46 PM
Author: Garry H (Cut Nut)

Ira all the AGS 0 stones with tables between 50 and 47% will be GIA Goods and a few might be Very Good.

There are many examples from AGS''s chart of ''candidates'' that - like the one shown here that get lower grades on the GIA''s facetware http://facetware.gia.edu/ HCA type web site.

Though the concern about confusion may be not only reasonable and logical, as well as consistent with your system of 3 types of ideals, including the FIC as a type that makes up, by your claim, one in 2000 identified, I find now that in the available set of 1156 round diamonds on the search by cut database, the smallest table is at 53 today, and have to wonder if the anticipated occurence of these possibly AGS0 stones that would also rank as GIA sub-excellent might not be very small, such that one might hardly worry, to speak of.

Then again, with my wife''s FIC in hand, maybe...what is that saying...I am calling the kettle black.

Regards,

Cutters would love to cut smaller tables and steeper crown angles - when the market and grading systems let them.

I have first hand experiance with one very switched on diamondtaire who will be introducing these things bit by bit so that his customers . >>

 

[oldminer]

Now we are told we are no smarter than frogs! Croak Croak.... If I see anyone get near that heater control and turn it up, I am going to jump out of the darned pot. Meanwhile, it sure is nice here in the warm pool.

 

[Paul-Antwerp]

Date: 9/1/2005 9:49:07 AM
Author: oldminer
Now we are told we are no smarter than frogs! Croak Croak....

Who cares if we are frogs.

Kermit can be our hero, and the pig loves us.

Live long,

 

[Garry H (Cut Nut)]

It will happen however - that clever cutters will want to polish a smaller % of these unusual stones where the yeild suits the rough.

But they need to test the market acceptance - if some frogs like the hot water, we will start to get a lot more FIC''s and BIC''s

 

[Regular Guy]

Two thoughts:

1) The frog thing...(eta - looking left, it's also my thing)...it's a story I tell when something draws the point of the experiment forward, to my mind, too, and...betting it was apocryphal, I tried it in Google. The odd result is not a ready documenting of the story, but the frequency with which the story is used to prove a point...

2) Garry, since you're raising the point about polish, or at least, I think you are...

Date: 9/1/2005 4:00:38 PM
Author: Garry H (Cut Nut)
It will happen however - that clever cutters will want to polish a smaller % of these unusual stones where the yeild suits the rough.

But they need to test the market acceptance - if some frogs like the hot water, we will start to get a lot more FIC's and BIC's

what is the idea with polish?

a) why is it important enough to be include as an item required by either GIA or AGS (and AGS wants it ideal to be ideal) to be good, but where it's universally de-emphasized.
b) what is it about these other kind of stone your pointing to, such that cutters will want to not polish some
c) is the rough analyzed in a way such that this style of cutting may be more "native" to it, and your point is that there is an organic-ness to the non-polishing you're getting at
d) isn't something similar said about 8-stars?
e) and...if some of these will not be polished, and if the polish will be required of them to earn the good grades from AGS or GIA...on the theory that they will not want to polish some of these anyway...what's stopping the cutters right now? They won't get a good grade even with the newly favored proportions, without the polish, so why not just not get the mediocre grade now?

 

[Garry H (Cut Nut)]

Ira that is one of your most obscure and difficult posts of all time

i think it deserves an award

I am not talking about "polish" as in polish and symmetry.

I am discussing the ''unusual'' proportions that AGS will now allow as AGS 0 - the ones that fall in FIC and BIC HCA proportion ranges, and those that have very small tables (of which i approve).

Cutters can decide to polish them to below 50% tables - but many clients will reject them, so clever cutters will start making stones for clients who will buy them and submit them to AGS. At first they might make 52%, then a few 51% and so on - testing the market.

Client buys, gets AGS 0, feels happy, tries a few 49%, tests his retailer clients ...and so on

meanwhile the yeild improves and everyone is a winner

 

[strmrdr]

Iv been playing around in diamcalc there are some combos with 47% crowns I sure would like to see in person in actual diamonds.
Yummy.
They appear to be pretty tough to cut however, even small variations in the angles went from yummy to just ok to yuk.

 

[Garry H (Cut Nut)]

One of my GAA Diploma of Diamond Technology students has submitted his review of the GIA cut grading system as part of the research supporting an oral presentation.

He has done an excellent job. But he has noted that GIA claims that their observation testing supports the virtual computer studies 9or vice a versa).

Look at one of the worst proportioned GIA Excellent stones on their Facetware.gia.edu site (shown below) that we have been studying at https://www.pricescope.com/community/threads/why-did-gia-included-steep-deep-diamonds-in-excellent.32135/

It has a WLR or Weighted Light Return of around 0.273 from their charts in the 1998 G&G publication.
High (Bright) > 2.85
Moderate 2.8-2.85
Typical 2.70 - 2.80
Moderately low 2.65 - 2.70
Low (dark)
The 2001 G&G Fire article charts indicate a DCLR (disperesed colored light return) of around 3.0

Above average >3.5
Average 2.8-3.5
Below average
Clearly this stone would have a lower range for typical or average for both light return and fire assuming it had optimum optical symmetry.

This begs 2 possible questions:

1. The GIA observation study and final system did not really use the decade long multi million dollar Virtual diamond computer based metrics or study.

2. The GIA's Excellent range includes many 'typical' or 'average' cut quality diamonds in its top grade (before even accounting for the negative effects that we could expect for lower quality optical symmetry).

 

[kenny]

I'm a novice who has learned a little about diamond cut grading.
I read these threads with great interest, but with very limited understanding.

I am struggling to come to a conclusion about the new GIA and AGS cut ratings.

Here is the conclusion I had about their old ratings. (Correct me if I'm wrong.)
AGS had a tighter standard for their top cut grade.
Every AGS 000 would qualify as a GIA Excellent.
But not every GIA Excellent would qualify as an AGS 000.

As a consumer I was assured a better cut by selecting an AGS 000 over a GIA Excellent. (Unless I got lucky and all the numbers on that GIA Excellent also fell within the AGS 000 specs.)

Now with the new standards neither AGS nor GIA has a tighter standard.
They are just different.
Buying the best cut will require more in-depth knowledge of cut than with the old systems.

OR, is it just to early to draw conclusions about the new systems?