2006 GIA grading report - Post info here please

[JohnQuixote]

Date: 1/10/2006 7:01:50 PM
Author: strmrdr

yep.
A lot of consumers have a misconception that the labs work for consumers.
They work for the sellers and are not an independant opinion on the diamonds grade and guarentee nothing.

They get too harsh and the industry will just find someone else to grade the diamonds with lower standards.

Right now ags has a nice niche market for themselves as graders for top cut diamonds so they can afford to be harsh because the market premium lets them.

1. GIA is trying to serve many masters. That seems certain.

2. Big picture: This is good for AGS. A lab of GIA’s size establishing a cut grade (even a broader one) makes AGS more desirable now... It’s an acknowledgment that AGS has been right for HAVING a cut grade these past 10 years.

...The longer GIA doesn’t address questions raised here, the better AGS looks.

...More people will become aware of cut grading now. They will ask questions

...New consumer: “Ok. What is this cut grade part? It says EX. Is EX the best?”

Sellers will have to answer that question where it was not even brought up before, so there is a better chance consumers will become aware of cut grading, including AGS, even if they go find the answers themselves.

 

[JohnQuixote]

Date: 1/10/2006 4:46:56 PM
Author: Paul-Antwerp

Date: 1/10/2006 12:32:51 PM
Author: JohnQuixote
A little bit of devil's advocate, fellows (and fellettes):

Setting aside the Facetware problems for a moment, I don't think we should knock GIA just for wanting to allow a broader range of taste in their top grade than AGS does.

For the majority of consumers in the pedestrian world GIA EX will be a better assurance of quality than they have had in the past, as it protects a buyer with regard to depth/spread, durability, polish & symmetry. It also reflects a cut quality that is well above average: In the real world, the vast number of diamonds sold without paper - or sent for grading by softer labs - far outweighs the number that will be graded by GIA or AGS. AGS Ideal may represent the very top of the global cut pyramid. GIA EX encompasses that range and then some (allowing for some configurations farther away from Tolkowsky - not necessarily a bad thing). Just because it does not meet the strict paradigms many of us here have personally embraced does not make it bad - it is still a quality assurance well above average.

For the second consecutive day, I beg to disagree with you, John. And this time, I have clearly re-read your post. Although, I wonder about that devil's advocate-part

Especially when you say GIA-EX will be a better assurance of quality than in the past, I fear that you are wrong. The average cutter, aiming to cut for a GIA-report, will be naturally inclined to go for the heaviest possible GIA-EX, and the Sarin-software will assist him in this. Remember, these are cutters, who mostly do not have the sophistication in judging cut that we have, and they will rely heavily on Sarin in choosing their proportion-sets.

In stead of improving their cut-quality, they will bring it down, by cutting a very high number of steep-deep GIA-EX's. Where they had the difficulty before of getting EX-EX on polish and symmetry, now, in order to get EX on the overall cut-grade, VG suffices on polish and symmetry.

So, the cutter wins a few % in extra weight, he can be more sloppy in polish and symmetry, and he is awarded with a grading-report, that includes a new feature, its cut-grade, which might even be a reason to sell it for more than a stone with an old GIA-report.

A fast-food-restaurant also has a great quality-assurance.

Live long,

LOL Paul. Our planets are merely aligned differently this week... You are right about the little devil, as you know very well that I am a tremendous fan of Peter, Jim, and all-things AGS. Still, for this thread I am going to continue as devil’s (GIA’s)

advocate in a big-picture sense.

Here is why cut-grading GIA is better than non-cut-grading GIA:

Your concerns about steep/deep are valid, but the new GIA grading protects consumers by preventing much WORSE diamonds from being sold under false pretenses. Remember, in the big picture, away from the trade & PS, uneducated consumers know only what they are told. Before now they could be easily hoodwinked with GIA reports on much worse diamonds.

Before

On the street, some sellers say that polish/sym = cut. They say table/depth & polish/sym = cut. They say all kinds of nonsense. Any poo-diamond with ex/ex polish/sym could be advertised as if it has best cut on the planet, and I’m talking dreck far outside the new EX grade.

After

Now true dreck and poo diamonds are held cut-accountable on GIA reports. Actually, they seem harder on shallow/shallow than AGS. You say cutters can target steep/deep within GIA’s EX paradigms. Ok, but do you realize the new GIA metric is stricter than AGS’ was at first?

41.5 / 35.8 was Ideal in AGS’ first release, but that combo won’t get GIA EX in cut.
41.2 / 35.8 still receives Ideal from AGS (if the cutter requests an old DQD) but it won’t get GIA EX in cut with D > 63%.

Just in case you think I am brainwashed... Do I believe the new GIA system has flaws? Absolutely. I am on record in this thread as saying so: Facetware and more accurate measurements are critical. CRITICAL. And I agree with Garry’s concerns about the lighting environment.

Still, on the whole, I prefer the GIA *with* a cut grading system to GIA without one.

I stand by my original statement: AGS’s new performance-based Ideal represents the top. GIA EX encompasses that range and then some, but it’s still a better assurance of quality than consumers had when any old dreck or poo could be sold as GIA-graded without a description of its cut.

 

[Garry H (Cut Nut)]

I have no time to explain this properlyu - but on the left are 3 different (very different) Sarin scans of the same stone - and the lower left also shows the recut plan to turn an already GIA Excellent into a GIA Excellent - even though this recut is impossible - making the table bigger!!!.

The top right is the accurate Helium scan.

Marty do you see the problem that GIA have with rounded data?

 

[michaelgem]

Re: John''s observation:

>>>>Now true dreck and poo diamonds are held cut-accountable on GIA reports. Actually, they seem harder on shallow/shallow than AGS. You say cutters can target steep/deep within GIA’s EX paradigms. Ok, but do you realize the new GIA metric is stricter than AGS’ was at first?p]

GIA believes it has valid data, from their 70+ thousand paired comparisons, to support the understanding that small variations in the negative direction from the Morse/Tolkowsky ideal 41, 34-35 degree angle combinations are more detrimental to optical performance than similar variations in the steep/deep direction. As John points out, this is reflected in their Facetware which penalizes shallow/shallow while giving the ok to slightly steep/deep.

This is a 180-degree change from their initial position that shallower angles were more brilliant. This change in position came from knowledge gained from their comparison testing. It is now in concert with observations by Basil Watermeyer and other cutters and my observations articulated in my 2000 article:

Hemphill et al. (199 reinforce the idea that shallow crown angles are better in relation to a diamond''s brilliance. Their study reported: "In general, WLR increases as crown angle decreases. “

Close up Observation and Diamond Photography Reveal the Opposite

These results run contrary to the present analysis of close-up viewing of diamonds with shallow crown angles between 28° and 32° compared to those between 33° and 36° when the pavilion is held close to 40.75° or 41°. Diamonds with shallow crown angles appear darker and less brilliant when viewed close-up.

Under the circumstances of close-up viewing, diamonds with as little as a 2.5° lower crown angle look less brilliant than those with crown angles of 34.5°. The same variation in crown angle in the opposite direction does not appear to produce this loss in brilliance compared to the ''Ideal''. “ >>>Michael Cowing, 2000.

(We are all aware of inverse adjustments between crown and pavilion to compensate this problem to an extent.)

IMO, the apparent, overall, relative darkness under close up viewing (or as Garry points out, due to lack of illumination in the vicinity of the viewers head) that is due to retro-reflection in the slightly shallow/shallow is more detrimental to optical performance than the middle ring darkness resulting from slightly steep/deep. (Devices like ASET, Firescope, and IS, because they lead to the overemphasis of light leakage on optical performance, may lead to the opposite belief.)

GIA’s data and Facetware now back up this rather fundamental observation. Of course, significant deviations in either the steep-deep or shallow-shallow amplify the detrimental optical performance of both ‘deviants’, and are no-no’s in both GIA’s and AGS’ systems.

Michael Cowing

www.acagemlab.com

 

[Serg]

Date: 1/11/2006 8:38:31 PM
Author: michaelgem

Re: John''s observation:

>>>>Now true dreck and poo diamonds are held cut-accountable on GIA reports. Actually, they seem harder on shallow/shallow than AGS. You say cutters can target steep/deep within GIA’s EX paradigms. Ok, but do you realize the new GIA metric is stricter than AGS’ was at first?<<<< John

GIA believes it has valid data, from their 70+ thousand paired comparisons, to support the understanding that small variations in the negative direction from the Morse/Tolkowsky ideal 41, 34-35 degree angle combinations are more detrimental to optical performance than similar variations in the steep/deep direction. As John points out, this is reflected in their Facetware which penalizes shallow/shallow while giving the ok to slightly steep/deep.

This is a 180-degree change from their initial position that shallower angles were more brilliant. This change in position came from knowledge gained from their comparison testing. It is now in concert with observations by Basil Watermeyer and other cutters and my observations articulated in my 2000 article:

<<<“WLR Indicates the Shallower the Crown Angle the More Brilliant the Diamond

Hemphill et al. (199 reinforce the idea that shallow crown angles are better in relation to a diamond''s brilliance. Their study reported: ''In general, WLR increases as crown angle decreases. “

Close up Observation and Diamond Photography Reveal the Opposite

These results run contrary to the present analysis of close-up viewing of diamonds with shallow crown angles between 28° and 32° compared to those between 33° and 36° when the pavilion is held close to 40.75° or 41°. Diamonds with shallow crown angles appear darker and less brilliant when viewed close-up.

Under the circumstances of close-up viewing, diamonds with as little as a 2.5° lower crown angle look less brilliant than those with crown angles of 34.5°. The same variation in crown angle in the opposite direction does not appear to produce this loss in brilliance compared to the ''Ideal''. “ >>>Michael Cowing, 2000.

(We are all aware of inverse adjustments between crown and pavilion to compensate this problem to an extent.)

IMO, the apparent, overall, relative darkness under close up viewing (or as Garry points out, due to lack of illumination in the vicinity of the viewers head) that is due to retro-reflection in the slightly shallow/shallow is more detrimental to optical performance than the middle ring darkness resulting from slightly steep/deep. (Devices like ASET, Firescope, and IS, because they lead to the overemphasis of light leakage on optical performance, may lead to the opposite belief.)

GIA’s data and Facetware now back up this rather fundamental observation. Of course, significant deviations in either the steep-deep or shallow-shallow amplify the detrimental optical performance of both ‘deviants’, and are no-no’s in both GIA’s and AGS’ systems.

Michael Cowing

www.acagemlab.com

Dear Michael,

Well done. Good attempt do defence GIA.
But half truth is worse than full mistake. It is pity for me to see such post from you.

1) GIA did not use head obscuration in 1998 work at all. It was one of main reasons of wrong results in old GIA study.

2) GIA used too big head obscuration last study . It is not good for final result too.
If you want to create good cut grading system for consumer you should use appropriate viewer conditions.
Close up Observation and Diamond Photography is far from normal consumer viewer conditions

3) It is not good to change comparison the pair: " ( lower crown and hight pavilion) and ( hight crown and hight pavilion)" to comparison the pair "( lower crown ) and ( hight crown ) " or to comparison the pair" ( lower crown and low pavilion) and ( hight crown and hight pavilion)".
It is not good way for researcher . Do not deceitful, please

Best regards, Sergey

 

[michaelgem]

Re:


It is not good to change comparison of the pair: " ( lower crown and higher pavilion) and ( higher crown and higher pavilion)" to a comparison of the pair "( lower crown ) and ( higher crown ) " or to a comparison of the pair" ( lower crown and low pavilion) and ( higher crown and higher pavilion)".
It is not good way for a researcher . Do not be deceitful, please>>> Sergey

Dear Sergey,

Because of my respect and admiration for you and your associates and the great contribution you all have made and continue to make to this industry, I am distressed that you see my post as deceitful. It was not at all my intention.

My intent was to give a balanced presentation of my understanding of GIA''s position, which I point out has undergone considerable revision. This revision in thinking was based upon the knowledge GIA researchers believe that they have gained from their extensive 70+ thousand paired comparison testing and subsequent stastical analysis. GIA reseachers believe that this knowledge base puts them on solid footing.

It was also my intent to point out that their current position is much more in concert with that of AGS and the diamond cutting industry. It is also much more in concert with anyone who recognises the truth of one of my conclusions in the 2000, Journal of Gemmology article:

>>

I have simply reported the facts as I currently see them.

Highest regards,

Michael

www.acagemlab.com

 

[Serg]

re:It was also my intent to point out that their current position is much more in concert with that of AGS and the diamond cutting industry.

I agree with " their current position is much more in concert with that of AGS and the diamond cutting industry".
Sorry, I can not do such conclusion from your previous post .
I will happy to be wrong .

Michael, may I ask whether you have any business affiliation with GIA ?

 

[michaelgem]

Re Sergey''s comments:

If you want to create good cut grading system for consumer you should use appropriate viewer conditions. Sergey

My latest article in the Journal of Gemmology is in agreement with this fundamental important statement. I said:

>>Michael


Close up Observation and Diamond Photography is far from normal consumer viewer conditions. Sergey

In that same article I said:

"In typical viewing circumstances that always include the viewer’s presence the superior beauty of the best-cut diamonds becomes apparent."

Referring to the contrast quality of brilliance I said:

"The factors that characterize the contrast quality of brilliance are the sharpness, number, sizes, and uniformity of the distribution of the diamond''s mosaic-appearing pattern of reflections. How can we assess this new quality of contrast brilliance?
The answer is simple.

All these aspects may be observed and evaluated from stationary images or ''snapshots'' of a diamond under a representation of typical viewing and illumination circumstances. "

There are several dangers and caveats to this last sentense including the difference between the camera''s mono vision and human binocular vision. IMO, as long as these are taken into account, this statement holds for not only contrast brilliance, but all aspects of perceived diamond beauty.

Michael Cowing

www.acagemlab.com

 

[JohnQuixote]

Date: 1/12/2006 10:12:16 AM
Author: michaelgem

It was also my intent to point out that their current position is much more in concert with that of AGS and the diamond cutting industry.

I agree, especially considering the way obscuration is being treated: AGS considers both 30 and 40 degrees of obscuration. Here are their comments, along with ASET projections.

(1) ASET/30 degrees of Obscuration: “It’s obvious why the steep/deep top right corner had to go away in the new system”

JQ: Note steep/deep not as desirable with 30 deg obs.

(Image Copyright AGS 2005, used with permission)

 

[JohnQuixote]

(2) AGS on 40 degrees of Obscuration: “The shallow/shallow or lower left corner stones start ‘paddling’ and they have lower dispersion readings”

JQ: Note shallow/shallow not as desirable with 40 deg obs.

(Image Copyright AGS 2005, used with permission)

 

[JohnQuixote]

My understanding (perhaps someone can confirm or deny) is that GIA used 46 degrees of obscuration in their metric. If so, it’s in-keeping with what AGS was projecting, and explains their strictness about shallow/shallow, even if there is disagreement on that point.

I stand by the notion that AGS’s new Ideal metric is stricter than it was and represents the top. GIA EX encompasses that range and then some, but they are not in disagreement with each other.

(This does not change the fact that GIA grading reports need to report the accurate numbers, to the tenth of a degree, etc.)

 

[adamasgem]

Date: 1/11/2006 6:56:42 PM
Author: Garry H (Cut Nut)
I have no time to explain this properlyu - but on the left are 3 different (very different) Sarin scans of the same stone - and the lower left also shows the recut plan to turn an already GIA Excellent into a GIA Excellent - even though this recut is impossible - making the table bigger!!!.

The top right is the accurate Helium scan.

Marty do you see the problem that GIA have with rounded data?

I haven''t filtered your specific data, but I guess you mean that how can you propose a recut when you round up or down to non-physically possible proportions, because the data is garbage.. GIGO

 

[Garry H (Cut Nut)]

Exactly Marty (refer to the set of scas at the top of the page)

Date: 1/12/2006 12:51:53 PM
Author: adamasgem

Date: 1/11/2006 6:56:42 PM
Author: Garry H (Cut Nut)
I have no time to explain this properlyu - but on the left are 3 different (very different) Sarin scans of the same stone - and the lower left also shows the recut plan to turn an already GIA Excellent into a GIA Excellent - even though this recut is impossible - making the table bigger!!!.

The top right is the accurate Helium scan.

Marty do you see the problem that GIA have with rounded data?

I haven''t filtered your specific data, but I guess you mean that how can you propose a recut when you round up or down to non-physically possible proportions, because the data is garbage.. GIGO

There are 3 scans from 2 different Sarin devices that show a far greater repeatablity error than the GIA''s rounding factors for most of the main parameters.

(Note to that the recut output ignores star ratio and lower girdle lengh - it is just an HCA type output)

 

[oldminer]

font>To be meaningful, measurements of diamond beauty should be made in illumination typical of circumstances in which human judgment of that beauty is made.">>>l


I agree with the part I highlighted in yellow.

I beg to disagreee with the second part which I highlighted in blue. I would suggest that the light does not need to be the same as a human would use to make this judgment. The lighting and the measuring of beauty must be found to correlate to what humans perceive, however, the lighting may well be substantially other than what any gemologist or expert would consider the light they would grade a diamond in for beauty with their own eyes. The variables measured should allow precise statistical correlation with human perception, but the lighting environment need not be the same as humans would prefer to use. Machines do not see as humans see. They need a differerent lighting environment to function. So long as gemologists and expert agree with the RESULTS, then we have a system which works.

 

[michaelgem]

David Atlas commented concerning the following highlighted statements of Michael Cowing:

- "Perception of beauty is everything."- To be meaningful, measurements of diamond beauty should be made in illumination typical of circumstances in which human judgment of that beauty is made.">>>


I beg to disagree with the second part which I highlighted in blue. I would suggest that the light does not need to be the same as a human would use to make this judgment. The lighting and the measuring of beauty must be found to correlate to what humans perceive, however, the lighting may well be substantially other than what any gemologist or expert would consider the light they would grade a diamond in for beauty with their own eyes. The variables measured should allow precise statistical correlation with human perception, but the lighting environment need not be the same as humans would prefer to use. Machines do not see as humans see. They need a different lighting environment to function. So long as gemologists and expert agree with the RESULTS, then we have a system which works.>>> David Atlas

I agree, David. Your words are a great elaboration on the fundamental idea I was communicating.

I intended your point to be implied by my words "in illumination typical of circumstances in which human judgment of that beauty is made".

Notice that I did not say: in typical illumination.

I mean to imply that the illumination used should produce optical performance to be measured that is close to optical performance that humans are seeing when they make their judgments. This is in order that consistent results are obtained between these measurements and human judgment in typical lighting circumstances.

If some unique lighting environment such as may be utilized by Imagem is necessary to obtain consistency between the machine and human judgment, it would meet this fundamental objective.

I do not want the implication of my words to be that the lighting environment need be the same as humans would prefer to use. Any suggestions for a terse rewording of the statement highlighted in blue?

How do you like : “To be meaningful, measurements of diamond beauty should be made in illumination producing optical performance closely approximating the optical performance judged by humans in usual illumination circumstances. “ ?

Michael Cowing

www.acagemlab.com

 

[oldminer]

Yup! That goes a long way in clearing the argument from the table. The essential thing in all diamond grading endeavors is to make proper grades from the data gathered. Whether this is done by eye, or by any machine method, the consistency and accuracy of the final outcome is most crucial.

Grading that is not accurate or not repeatable will become an obsolete style of doing business. This style will persist for a while while new standards develop, but I foresee a time where newer, more accurate grading will be what consumers, dealers and site-holders will all expect and demand.

 

[adamasgem]

Date: 1/12/2006 4:56:44 PM
Author: oldminer
Yup! That goes a long way in clearing the argument from the table. The essential thing in all diamond grading endeavors is to make proper grades from the data gathered. Whether this is done by eye, or by any machine method, the consistency and accuracy of the final outcome is most crucial.

Grading that is not accurate or not repeatable will become an obsolete style of doing business. This style will persist for a while while new standards develop, but I foresee a time where newer, more accurate grading will be what consumers, dealers and site-holders will all expect and demand.

Machines may solve the problem of repeatability vis-a-vie human subjectivity..

"Accuracy" (i.e. the "correct answer") IS highly dependent on the environment selected to determine the baseline, especially in the case being discussed.

The problem is in defining the "right question" and envirionments(s) and viewpoint(s) that will result in a meaningfull composite metric (or opinion) for the consumer.

Certainly, taking the most accurate measurements possibile and then arbitrarily screwing up the data to cloud and distort the "correct answer" is clearly WRONG..

 

[Garry H (Cut Nut)]

Date: 1/12/2006 12:42:14 PM
Author: JohnQuixote

My understanding (perhaps someone can confirm or deny) is that GIA used 46 degrees of obscuration in their metric. If so, it’s in-keeping with what AGS was projecting, and explains their strictness about shallow/shallow, even if there is disagreement on that point.

I stand by the notion that AGS’s new Ideal metric is stricter than it was and represents the top. GIA EX encompasses that range and then some, but they are not in disagreement with each other.

(This does not change the fact that GIA grading reports need to report the accurate numbers, to the tenth of a degree, etc.)

Sorry guys - there is no way AGS would support a 46 degree head obstruction.
I think it has more to do with the sizes of salad bowls GIA Cut Study team were able to buy at Crate and Barrel.
This 41.2P 35.8C 47% stone has far too much blue.

Michael are you on the gIA payroll?

 

[Garry H (Cut Nut)]

Date: 1/12/2006 5:43:44 PM
Author: adamasgem

Machines may solve the problem of repeatability vis-a-vie human subjectivity..

Certainly, taking the most accurate measurements possibile and then arbitrarily screwing up the data to cloud and distort the ''correct answer'' is clearly WRONG..

Marty in the light of your comments to Dave - have a very close look at the recut sarin sticker from my data image above.
You will find some very strange logic.
The only reason I can suggest as to why the Sarin Facetware software could suggest a physically impossible recutting excercise (i.e. making the table larger, the crown angle a little smaller, all without changing the the total depth by more than the 0.1% taken off the pavilion angle / depth) is very very strange for a computer program.
It surely suggests that the data presented is actually not what the scanned data actually is - i.e. the Sarin reported data is manipulated and is not the REAL data.

It may come as no surprise that many diamond cutters who own 30 or 40 rough allocation scanners are not very happy about paying $3500 per machine, and an annual renewal fee, for this Facetware(tm) software.

Any ideas as to what is really happening?

 

[belle]

Date: 1/12/2006 6:22:59 PM
Author: Garry H (Cut Nut)

Date: 1/12/2006 5:43:44 PM
Author: adamasgem

Machines may solve the problem of repeatability vis-a-vie human subjectivity..

Certainly, taking the most accurate measurements possibile and then arbitrarily screwing up the data to cloud and distort the 'correct answer' is clearly WRONG..

Marty in the light of your comments to Dave - have a very close look at the recut sarin sticker from my data image above.
You will find some very strange logic.
The only reason I can suggest as to why the Sarin Facetware software could suggest a physically impossible recutting excercise (i.e. making the table larger, the crown angle a little smaller, all without changing the the total depth by more than the 0.1% taken off the pavilion angle / depth) is very very strange for a computer program.
It surely suggests that the data presented is actually not what the scanned data actually is - i.e. the Sarin reported data is manipulated and is not the REAL data.

It may come as no surprise that many diamond cutters who own 30 or 40 rough allocation scanners are not very happy about paying $3500 per machine, and an annual renewal fee, for this Facetware(tm) software.

Any ideas as to what is really happening?

great question garry. if this thread wasn't so bogged down with helium commercials and imagem commercials and gia commercials we might actually be able to get to the bottom of this.

 

[JohnQuixote]

Date: 1/12/2006 6:02:36 PM
Author: Garry H (Cut Nut)

Date: 1/12/2006 12:42:14 PM
Author: JohnQuixote


My understanding (perhaps someone can confirm or deny) is that GIA used 46 degrees of obscuration in their metric. If so, it’s in-keeping with what AGS was projecting, and explains their strictness about shallow/shallow, even if there is disagreement on that point.

I stand by the notion that AGS’s new Ideal metric is stricter than it was and represents the top. GIA EX encompasses that range and then some, but they are not in disagreement with each other.

(This does not change the fact that GIA grading reports need to report the accurate numbers, to the tenth of a degree, etc.)

Sorry guys - there is no way AGS would support a 46 degree head obstruction.
I think it has more to do with the sizes of salad bowls GIA Cut Study team were able to buy at Crate and Barrel.
This 41.2P 35.8C 47% stone has far too much blue.

Michael are you on the gIA payroll?

We know AGS did not Garry. Do we know if GIA actually used 46 degrees in their metric? I offered that number based on what I had heard and it seems possible, but not confirmed.

Tongue-in-cheek, perhaps it''s b/c the sun is more hidden in CA than in NV. All those palm trees, you know.

 

[Garry H (Cut Nut)]

Edited

Oops- there was another page

Good question John.
No- it seems they did not - it was worse than that - far worse.
The largest number of their observations were made thru a dome that (if I read it right http://www.gia.edu/pdfs/cut_table_1.pdf ) were black for 80 degrees (with a 20 degree peep hole).

Wrong - by far the largest number were at 45 with the upper zone white (+5,000) , and 46 black (+5000).
Ignore that image - there were only 756 at the 80 degree black.

 

[JohnQuixote]

Date: 1/12/2006 7:01:18 PM
Author: Garry H (Cut Nut)
Edited

Oops- there was another page

Good question John.
No- it seems they did not - it was worse than that - far worse.
The largest number of their observations were made thru a dome that (if I read it right http://www.gia.edu/pdfs/cut_table_1.pdf ) were black for 80 degrees (with a 20 degree peep hole).

Wrong - by far the largest number were at 45 with the upper zone white (+5,000) , and 46 black (+5000).
Ignore that image - there were only 756 at the 80 degree black.

Can you concise that Garry?

Belle, if you're referring to me I am not making a commercial for GIA at all here. I started by haranguing them on P3 with FW adjustments and continue to madd-harangue them for this rounding folly on grading reports. You may know we send our premium diamonds to the AGS because our own philosophy of direct performance observation is in-line with their methodology. I'm merely trying to give GIA a fair shake here.

For anyone, I'd simply ask this: Take AGS completely out of the picture. Gone. Poof...

Now, would you rather have GIA as it was pre-2006, or GIA with a cut grade?

 

[strmrdr]

Date: 1/12/2006 7:32:32 PM
Author: JohnQuixote

Date: 1/12/2006 7:01:18 PM


Now, would you rather have GIA as it was pre-2006, or GIA with a cut grade?

pre-2006

I allready know how to find the diamonds I want to buy :}
more demand == higher prices therefore more people finding them is a bad thing.
Besides I can see it now:

a: is this the most awesome diamond in the world, gia says it rates EX
me: no its steep/deep
a: lier gia says its EX and you dont know what your talking about.
me: well then buy it.
a: someone on another forum said gia EX are the the best diamonds in the world.
me: well buy it then
a: why would you call it steep/deep gia says its perfect.
me: BUY IT AND BUZZ OFF!
a: sheesh dont have to get rude
me: (middle finger icon) mutters poor misguided morons who dont listen.

GIA should do it right or not at all.

hmmmm i should make that into a play!

 

[RockDoc]

John Q asks:

For anyone, I''d simply ask this: Take AGS completely out of the picture. Gone. Poof...
Now, would you rather have GIA as it was pre-2006, or GIA with a cut grade?
____________________________________________________________

The answer to that would depend on your stance on things:

A consumer would prefer the cut grade system
A cutter or dealer selling Ideal Cuts and H&A would rather have the newer ( as long as it made their stones look good)
A guy selling average or price point merchandise would not want to see the change.

If it wasn''t for AGS taking bite out of GIA''s cert biz, I don''t believe we''d ever see a GIA CUT grade like we are seeing now.It didn''t happen for over 30 years so I think AGS caused GIA to "wake up and smell the coffee".

However, if it isn''t accurate then NO cut grade is better than a system that defies logic and is misleading which results in someone who is relying on the assumption of getting at least a level of reasonbly correct information , particularly when there is a fee to pay.

Rockdoc

 

[RockDoc]

Storm :

hmmmm i should make that into a play!



Storm you''re already YEARS late.......... It already is a play....maybe it even qualifies as a Soap!


Rockdoc

 

[Capitol Bill]

Date: 1/12/2006 7:57:43 PM
Author: strmrdr

GIA should do it right or not at all.

Amen. Now that''s concise!
Bill

 

[adamasgem]

Date: 1/12/2006 6:22:59 PM
Author: Garry H (Cut Nut)

Date: 1/12/2006 5:43:44 PM
Author: adamasgem

Machines may solve the problem of repeatability vis-a-vie human subjectivity..

Certainly, taking the most accurate measurements possibile and then arbitrarily screwing up the data to cloud and distort the ''correct answer'' is clearly WRONG..

Marty in the light of your comments to Dave - have a very close look at the recut sarin sticker from my data image above.
You will find some very strange logic.
The only reason I can suggest as to why the Sarin Facetware software could suggest a physically impossible recutting excercise (i.e. making the table larger, the crown angle a little smaller, all without changing the the total depth by more than the 0.1% taken off the pavilion angle / depth) is very very strange for a computer program.
It surely suggests that the data presented is actually not what the scanned data actually is - i.e. the Sarin reported data is manipulated and is not the REAL data.

It may come as no surprise that many diamond cutters who own 30 or 40 rough allocation scanners are not very happy about paying $3500 per machine, and an annual renewal fee, for this Facetware(tm) software.

Any ideas as to what is really happening?

Garry..

By rerounding so that the diameter goes down (7.19-->7.1, the table percentage goes up automatically, even though you havent touched the table physically

Also Don''t forget Sarin is quantized at 0.1 degree increments so that you don''t need to change a facet angle by 0.1 degree to get that much indicated change in the number, you only have to change it by 0.01 degree, and voila, rounding gets you from 0.0 to 0.1 if the truth was originally 0.04 +0.01 = 0.05, rounded, gives you 0.1

Make the #''s work to bump the grade..

Funny thing is, is that the FARCEWARE round for the original and the recut gives you the same inputs

Depth % remains the same 62.9%
Table: 55.7 to 56.1 is still a GIA 56%
Crown 35.7 to 35.6 is still a GIA 35.5
Crown height goes up but that is not a FARCEWARE input
3.5 and 3.3% is still a medium girdle
Pav Ang 41.4 to 41.3 is still a GIA 41.4

I know

, it is done with smoke and mirrors

Are GIA and SARIN sleeping in the same bed

Ma

 

[michaelgem]

Belle,

Do you really see the efforts at educational interaction and understanding going on here as "helium commercials and imagem commercials and gia commercials"?

Garry,

I am surprised that you and Sergey would wonder if I had some affiliation with GIA. I have none.

I feel, as perhaps John does, that more can be gained by learning what the GIA says concerning their cut grading methodology, than simply trash talking it. Belle might "get to the bottom of this" better by presenting these questions, as I am, directly to the GIA.

There is the possibility that some, but not all, of the problems discussed in this thread may come to rest at Sarin''s doorstep. It was pointed out that GIA uses their own software, called Horizon, that takes as input only the raw unprocessed data from the Sarin. The implication is that Sarin’s software does not produce the same output from the raw data.

If there are inconsistencies between GIA and Sarin, I suppose it begs the question: Does GIA have an obligation to straighten out Sarin, so they get results consistent with the GIA labs? Or should GIA provide as open source the software algorithm describing how the raw data is processed ?

Michael Cowing

www.acagemlab.com

 

[Garry H (Cut Nut)]

Date: 1/12/2006 10:42:28 PM
Author: adamasgem

Garry..

By rerounding so that the diameter goes down (7.19-->7.1, the table percentage goes up automatically, even though you havent touched the table physically I just checked this Marty and it changes by 0.1% - not enough to get 55.7% to 56.1% - and that is aside from the fact that lowering the crown angle must make the table SMALLER not bigger by +0.1% - so even allowing for all the rounding and diameter reduction factors you mention - this is impossible - so the algoritms are ?????????

Also Don''t forget Sarin is quantized at 0.1 degree increments so that you don''t need to change a facet angle by 0.1 degree to get that much indicated change in the number, you only have to change it by 0.01 degree, and voila, rounding gets you from 0.0 to 0.1 if the truth was originally 0.04 +0.01 = 0.05, rounded, gives you 0.1

Make the #''s work to bump the grade..

Funny thing is, is that the FARCEWARE round for the original and the recut gives you the same inputs - That was my point - if this stone was indeed sitting on some sort of knife edge that the online service does not allow us to resolve - then the recalculation software is really dumb.

Depth % remains the same 62.9%
Table: 55.7 to 56.1 is still a GIA 56%
Crown 35.7 to 35.6 is still a GIA 35.5
Crown height goes up but that is not a FARCEWARE input
3.5 and 3.3% is still a medium girdle
Pav Ang 41.4 to 41.3 is still a GIA 41.4

Are GIA and SARIN sleeping in the same bed

Sarin are GIA''s resellers - they both have an interest in selling this software package - but we were promised there would be a chart made available for appraisers - which is apperantly "at the printer". Very slow printers

Me thinks the sales of software will die immediately the printers have finished their work (that has taken more than 6 months).

BTW is it fair and reasonable for a not for profit authority to sell the result of industry funded research?

Ma

Micheal I am glad to hear you are not being paid by GIA. Some of your posts this year seemed to indicate differently.

I also appreciate you are giving GIA some rope - but do you approve of the use of light colored trays that allow leakage ?

Do you approve of the CVE vieweing light box (that has an open back where different lighting was available in the many different locations where it was employed).

Do you approve of 45 degree light obstruction? What would be an acceptable amount or range of obscfuration?