AGS introduces cut grading on DQR reports

[strmrdr]

AGS Gold can not tell these 2 stones apart.

AGS PGS did.

https://www.pricescope.com/community/threads/when-are-is-aset-and-or-reflector-technologies-needed-or-not-needed-for-internet-purchasing%E2%80%A6.99277/

This is what I'm talking about when I say Gold is a shotgun it just shoots a grade out in the general very wide area where PGS is more like a rifle bullet and hits the target in a fairly accurate fashion!

I rest my case, AGS Gold stinks for consumers.

 

[diagem]

Date: 11/7/2008 11:28:46 AM
Author: strmrdr
AGS Gold can not tell these 2 stones apart.

AGS PGS did.

https://www.pricescope.com/community/threads/when-are-is-aset-and-or-reflector-technologies-needed-or-not-needed-for-internet-purchasing%E2%80%A6.99277/

This is what I''m talking about when I say Gold is a shotgun it just shoots a grade out in the general very wide area where PGS is more like a rifle bullet and hits the target in a fairly accurate fashion!

I rest my case, AGS Gold stinks for consumers.

Why? You think it crosses the thin line of the shallow pavilion border?

 

[oldminer]

Strmrdr, I see the nice IS images and can readily see they are not identical. However, the burning question is how much difference can the human eye, both the novice and the trained diamond professional see when looking at two such stones? I am certain the IS is a tool which allows us to know there are differences, but I often find some of the differences are nominal in actual, visual appearance. I know we do not have smooth metrics to better define gray areas which are rather broad at the junctions of each cut grade at the present time, so how would you know or show that these two diamonds actually look different from one another to observers?

I don't believe I have a definitive way to know how differently these two would look. I know I could use direct assessment or probably ray-tracing to give me some numerical results, but still, would I see a difference or would I just wonder if this little bit made a difference? THANKS.

 

[Serg]

Date: 11/7/2008 1:49:43 PM
Author: oldminer
Strmrdr, I see the nice IS images and can readily see they are not identical. However, the burning question is how much difference can the human eye, both the novice and the trained diamond professional see when looking at two such stones? I am certain the IS is a tool which allows us to know there are differences, but I often find some of the differences are nominal in actual, visual appearance. I know we do not have smooth metrics to better define gray areas which are rather broad at the junctions of each cut grade at the present time, so how would you know or show that these two diamonds actually look different from one another to observers?

I don't believe I have a definitive way to know how differently these two would look. I know I could use direct assessment or probably ray-tracing to give me some numerical results, but still, would I see a difference or would I just wonder if this little bit made a difference? THANKS.

re:would I see a difference or would I just wonder if this little bit made a difference? THANKS.


more questions. If somebody see difference, will he see all times worse appearance for stones with Leakage?? Could stone with leakage ( bigger than in H&A) have better appearance( for example fire is definitely better , but Brilliancy is same) ??? Of course some stones with strong leakage is not nice. Bit why if Stone has Leakage , its can not be nice? Any proof?

 

[diagem]

Date: 11/7/2008 2:04:03 PM
Author: Serg

Date: 11/7/2008 1:49:43 PM
Author: oldminer
Strmrdr, I see the nice IS images and can readily see they are not identical. However, the burning question is how much difference can the human eye, both the novice and the trained diamond professional see when looking at two such stones? I am certain the IS is a tool which allows us to know there are differences, but I often find some of the differences are nominal in actual, visual appearance. I know we do not have smooth metrics to better define gray areas which are rather broad at the junctions of each cut grade at the present time, so how would you know or show that these two diamonds actually look different from one another to observers?

I don''t believe I have a definitive way to know how differently these two would look. I know I could use direct assessment or probably ray-tracing to give me some numerical results, but still, would I see a difference or would I just wonder if this little bit made a difference? THANKS.

re:would I see a difference or would I just wonder if this little bit made a difference? THANKS.


more questions. If somebody see difference, will he see all times worse appearance for stones with Leakage?? Could stone with leakage ( bigger than in H&A) have better appearance( for example fire is definitely better , but Brilliancy is same) ??? Of course some stones with strong leakage is not nice. Bit why if Stone has Leakage , its can not be nice? Any proof?

Do you know any cut that has NO leakage at a certain view??? I dont.

 

[Serg]

Date: 11/7/2008 2:07:36 PM
Author: DiaGem

Date: 11/7/2008 2:04:03 PM
Author: Serg

Date: 11/7/2008 1:49:43 PM
Author: oldminer
Strmrdr, I see the nice IS images and can readily see they are not identical. However, the burning question is how much difference can the human eye, both the novice and the trained diamond professional see when looking at two such stones? I am certain the IS is a tool which allows us to know there are differences, but I often find some of the differences are nominal in actual, visual appearance. I know we do not have smooth metrics to better define gray areas which are rather broad at the junctions of each cut grade at the present time, so how would you know or show that these two diamonds actually look different from one another to observers?

I don''t believe I have a definitive way to know how differently these two would look. I know I could use direct assessment or probably ray-tracing to give me some numerical results, but still, would I see a difference or would I just wonder if this little bit made a difference? THANKS.

re:would I see a difference or would I just wonder if this little bit made a difference? THANKS.


more questions. If somebody see difference, will he see all times worse appearance for stones with Leakage?? Could stone with leakage ( bigger than in H&A) have better appearance( for example fire is definitely better , but Brilliancy is same) ??? Of course some stones with strong leakage is not nice. But why if Stone has Leakage , its can not be nice? Any proof?

Do you know any cut that has NO leakage at a certain view??? I dont.

reo you know any cut that has NO leakage at a certain view??? I dont.


Diagem,
pleases ee remark .. ( bigger than in H&A)

 

[diagem]

Date: 11/7/2008 2:28:10 PM
Author: Serg

Date: 11/7/2008 2:07:36 PM
Author: DiaGem

Date: 11/7/2008 2:04:03 PM
Author: Serg

Date: 11/7/2008 1:49:43 PM
Author: oldminer
Strmrdr, I see the nice IS images and can readily see they are not identical. However, the burning question is how much difference can the human eye, both the novice and the trained diamond professional see when looking at two such stones? I am certain the IS is a tool which allows us to know there are differences, but I often find some of the differences are nominal in actual, visual appearance. I know we do not have smooth metrics to better define gray areas which are rather broad at the junctions of each cut grade at the present time, so how would you know or show that these two diamonds actually look different from one another to observers?

I don''t believe I have a definitive way to know how differently these two would look. I know I could use direct assessment or probably ray-tracing to give me some numerical results, but still, would I see a difference or would I just wonder if this little bit made a difference? THANKS.

re:would I see a difference or would I just wonder if this little bit made a difference? THANKS.


more questions. If somebody see difference, will he see all times worse appearance for stones with Leakage?? Could stone with leakage ( bigger than in H&A) have better appearance( for example fire is definitely better , but Brilliancy is same) ??? Of course some stones with strong leakage is not nice. But why if Stone has Leakage , its can not be nice? Any proof?

Do you know any cut that has NO leakage at a certain view??? I dont.

reo you know any cut that has NO leakage at a certain view??? I dont.


Diagem,
pleases ee remark .. ( bigger than in H&A)

Serg..., I saw that remark...

Leakage is part of the beauty!

Bigger than H&A..., or not!

 

[Serg]

Bruce, Marty

Id zone has 60 cells
PGS0 zone has 88 cells
Intersection Id and PGS0 zones has 53 cells
Union of Id and PGS0 zones has 95 sets

Early I calculate correlation like Intersection/ Union of sets=53/95=56%

I did not find definition for correlation between two sets in Internet. ( remember what we received it on first courses MSU. 20+ years ago)

If I use random functions with uniform distribution on these sets( A, B) , I have correlation function between two random functions (M( (A - MA) * (B - MB))/ (sqrt( DA * DB )), M is mathematical expectation
D is dispersion



So correlation is : (M(AB)-MAMB)/sqrt(DADB)

(Intersection) / sgrt(( area “Id”)*(area”0”))=53/72.6=73%



What definition for correlation between two sets Do you know?

 

[oldminer]

I appreciate what Serg and DiaGem have said. Leakage is part of the diamond''s physical propertis. Some is good and too much is not good.

My question was about the two IS images in particular. Who is to say that one is definitely prettier than the other? We can see one has more leakage, but not a whole lot. Yet, are they both highly attractive? Who or which organization is the qualified arbitor of such a determination? I believe the consumer and the experts are the best judges of this, but it remains subjective and qualitative.

The finer gradations of quality which come into accepted use will help us to define the value and the market price.

 

[adamasgem]

Date: 11/7/2008 3:37:29 PM
Author: Serg

Bruce, Marty

Id zone has 60 cells
PGS0 zone has 88 cells
Intersection Id and PGS0 zones has 53 cells
Union of Id and PGS0 zones has 95 sets

Early I calculate correlation like Intersection/ Union of sets=53/95=56%

I did not find definition for correlation between two sets in Internet. ( remember what we received it on first courses MSU. 20+ years ago)

If I use random functions with uniform distribution on these sets( A, B) , I have correlation function between two random functions (M( (A - MA) * (B - MB))/ (sqrt( DA * DB )), M is mathematical expectation
D is dispersion




So correlation is : (M(AB)-MAMB)/sqrt(DADB)

(Intersection) / sgrt(( area “Id”)*(area”0”))=53/72.6=73%




What definition for correlation between two sets Do you know?

So you have a correlation between apples and oranges, so what.

A "grade" (GOLD) and a PGS region where you have a 100% probability of getting a grade for a very specific SPECIFIC innovation. (set of perfectly symmetric parameters, and subset of the rest of the parameter sets), if you could cut it.

Also, did you run the mix of stars and lgf''s and girdle thicknesses used to create the GOLD set to generate your PGS 0 chart. Let alone the tilts.

Sorry Sergey, I don''t see the relevance. They are two different systems. EVEN the AGS PGS Charts are NO GUARANTEE of the grade, as the symmetry and weight criteria have to be met.

It is a waste of time, if not misleading arguement, because of looser and different criteria in the generation of the GOLD charts.

 

[Regular Guy]

Date: 11/7/2008 11:28:46 AM
Author: strmrdr
AGS Gold can not tell these 2 stones apart.

AGS PGS did.

https://www.pricescope.com/community/threads/when-are-is-aset-and-or-reflector-technologies-needed-or-not-needed-for-internet-purchasing%E2%80%A6.99277/

This is what I'm talking about when I say Gold is a shotgun it just shoots a grade out in the general very wide area where PGS is more like a rifle bullet and hits the target in a fairly accurate fashion!

I rest my case, AGS Gold stinks for consumers.

I don't think you should rest just yet...

Dave and particularly Serg's suggestion that leakage may be attractive...is prompted by what...

We don't want things turning upside down precipitously.

The diamonds featured here were recently called forward on the contemporary thread here.

But...unless I am corrected, it is the leaky one that gets the zero.

Although your point here, Karl, seems to be that PGS knows which is which...the one PGS picks seems to be, unless I've misread the source text...the one we would more conventionally say: "pass"

Are we even considering the leaky stone as possibly attractive because of what seems to be sound proportion numbers? Really, were it not for the numbers...just seeing the IS...we would conventionally say pass!

And...we say it every day here. In the example of this thread...we say...yeah, who's to say...maybe it's nice.

I'd rather not make too much of this yet, because I would like confirmation from Jonathan.

But, as you've said in this thread, Karl, and as many say daily, test with reflectors and feel confident in your purchase.

Is this case an exception?

Is PGS a better and different arbiter?

For my money, this is a first question to answer, before comparing to gold, which, intuitively, is more feeble, yes.

(and by the way...though maybe my language is not rigorously applied...I really think intuitively measurement error describes in a meaningful way what should be the difference between gold and platinum, since...I'm thinking now the main difference is really in how many variables you are considering...with more yielding a closer fit, and therefore better description...but until the above is clarified...this is a mere p.s.)...

 

[strmrdr]

Date: 11/7/2008 4:34:31 PM
Author: Regular Guy


But...unless I am corrected, it is the leaky one that gets the zero.

consider yourself corrected

We need a handshake smiley.

 

[strmrdr]

Date: 11/7/2008 1:49:43 PM
Author: oldminer
Strmrdr, I see the nice IS images and can readily see they are not identical. However, the burning question is how much difference can the human eye, both the novice and the trained diamond professional see when looking at two such stones? I am certain the IS is a tool which allows us to know there are differences, but I often find some of the differences are nominal in actual, visual appearance. I know we do not have smooth metrics to better define gray areas which are rather broad at the junctions of each cut grade at the present time, so how would you know or show that these two diamonds actually look different from one another to observers?


I don''t believe I have a definitive way to know how differently these two would look. I know I could use direct assessment or probably ray-tracing to give me some numerical results, but still, would I see a difference or would I just wonder if this little bit made a difference? THANKS.

From experience...
There would be a clear difference in appearance that I would instantly notice in anything but strong direct lighting and maybe even then.

 

[strmrdr]

Date: 11/7/2008 2:04:03 PM
Author: Serg

Date: 11/7/2008 1:49:43 PM

Author: oldminer

Strmrdr, I see the nice IS images and can readily see they are not identical. However, the burning question is how much difference can the human eye, both the novice and the trained diamond professional see when looking at two such stones? I am certain the IS is a tool which allows us to know there are differences, but I often find some of the differences are nominal in actual, visual appearance. I know we do not have smooth metrics to better define gray areas which are rather broad at the junctions of each cut grade at the present time, so how would you know or show that these two diamonds actually look different from one another to observers?


I don't believe I have a definitive way to know how differently these two would look. I know I could use direct assessment or probably ray-tracing to give me some numerical results, but still, would I see a difference or would I just wonder if this little bit made a difference? THANKS.

re:would I see a difference or would I just wonder if this little bit made a difference? THANKS.



more questions. If somebody see difference, will he see all times worse appearance for stones with Leakage?? Could stone with leakage ( bigger than in H&A) have better appearance( for example fire is definitely better , but Brilliancy is same) ??? Of course some stones with strong leakage is not nice. Bit why if Stone has Leakage , its can not be nice? Any proof?

sure a stone with strong leakage can blow any size comparable RB out of the water ... if its an asscher :}
But take away LR in an RB and you have nothing left but an ugly expensive chunk of carbon.

 

[Garry H (Cut Nut)]

Date: 11/7/2008 2:55:51 PM
Author: DiaGem

Date: 11/7/2008 2:28:10 PM
Author: Serg

Date: 11/7/2008 2:07:36 PM
Author: DiaGem

Date: 11/7/2008 2:04:03 PM
Author: Serg

Date: 11/7/2008 1:49:43 PM
Author: oldminer
Strmrdr, I see the nice IS images and can readily see they are not identical. However, the burning question is how much difference can the human eye, both the novice and the trained diamond professional see when looking at two such stones? I am certain the IS is a tool which allows us to know there are differences, but I often find some of the differences are nominal in actual, visual appearance. I know we do not have smooth metrics to better define gray areas which are rather broad at the junctions of each cut grade at the present time, so how would you know or show that these two diamonds actually look different from one another to observers?

I don''t believe I have a definitive way to know how differently these two would look. I know I could use direct assessment or probably ray-tracing to give me some numerical results, but still, would I see a difference or would I just wonder if this little bit made a difference? THANKS.

re:would I see a difference or would I just wonder if this little bit made a difference? THANKS.


more questions. If somebody see difference, will he see all times worse appearance for stones with Leakage?? Could stone with leakage ( bigger than in H&A) have better appearance( for example fire is definitely better , but Brilliancy is same) ??? Of course some stones with strong leakage is not nice. But why if Stone has Leakage , its can not be nice? Any proof?

Do you know any cut that has NO leakage at a certain view??? I dont.

reo you know any cut that has NO leakage at a certain view??? I dont.


Diagem,
pleases ee remark .. ( bigger than in H&A)

Serg..., I saw that remark...

Leakage is part of the beauty!

Bigger than H&A..., or not!

In step cut stones leakage can become a positive part of the patern creation, along with head obstruction dark zones.
The same can be of some value in crushed ice style radiants and cushions etc.

But for a round diamond - the leakage inside the table area as per Storm''s example - will not be a good contributor to contrast.

It will however be a negative contribution to the wearers pleasure once the stone is dirty - in this case that area will return little light or fire.

 

[diagem]

Date: 11/7/2008 4:53:59 PM
Author: strmrdr

Date: 11/7/2008 2:04:03 PM
Author: Serg

Date: 11/7/2008 1:49:43 PM

Author: oldminer

Strmrdr, I see the nice IS images and can readily see they are not identical. However, the burning question is how much difference can the human eye, both the novice and the trained diamond professional see when looking at two such stones? I am certain the IS is a tool which allows us to know there are differences, but I often find some of the differences are nominal in actual, visual appearance. I know we do not have smooth metrics to better define gray areas which are rather broad at the junctions of each cut grade at the present time, so how would you know or show that these two diamonds actually look different from one another to observers?


I don''t believe I have a definitive way to know how differently these two would look. I know I could use direct assessment or probably ray-tracing to give me some numerical results, but still, would I see a difference or would I just wonder if this little bit made a difference? THANKS.

re:would I see a difference or would I just wonder if this little bit made a difference? THANKS.



more questions. If somebody see difference, will he see all times worse appearance for stones with Leakage?? Could stone with leakage ( bigger than in H&A) have better appearance( for example fire is definitely better , but Brilliancy is same) ??? Of course some stones with strong leakage is not nice. Bit why if Stone has Leakage , its can not be nice? Any proof?

sure a stone with strong leakage can blow any size comparable RB out of the water ... if its an asscher :}
But take away LR in an RB and you have nothing left but an ugly expensive chunk of carbon.

LR = ?

 

[Serg]

Date: 11/7/2008 4:55:15 PM
Author: Garry H (Cut Nut)

Date: 11/7/2008 2:55:51 PM
Author: DiaGem

Date: 11/7/2008 2:28:10 PM
Author: Serg

Date: 11/7/2008 2:07:36 PM
Author: DiaGem

Date: 11/7/2008 2:04:03 PM
Author: Serg

Date: 11/7/2008 1:49:43 PM
Author: oldminer
Strmrdr, I see the nice IS images and can readily see they are not identical. However, the burning question is how much difference can the human eye, both the novice and the trained diamond professional see when looking at two such stones? I am certain the IS is a tool which allows us to know there are differences, but I often find some of the differences are nominal in actual, visual appearance. I know we do not have smooth metrics to better define gray areas which are rather broad at the junctions of each cut grade at the present time, so how would you know or show that these two diamonds actually look different from one another to observers?

I don''t believe I have a definitive way to know how differently these two would look. I know I could use direct assessment or probably ray-tracing to give me some numerical results, but still, would I see a difference or would I just wonder if this little bit made a difference? THANKS.

re:would I see a difference or would I just wonder if this little bit made a difference? THANKS.


more questions. If somebody see difference, will he see all times worse appearance for stones with Leakage?? Could stone with leakage ( bigger than in H&A) have better appearance( for example fire is definitely better , but Brilliancy is same) ??? Of course some stones with strong leakage is not nice. But why if Stone has Leakage , its can not be nice? Any proof?

Do you know any cut that has NO leakage at a certain view??? I dont.

reo you know any cut that has NO leakage at a certain view??? I dont.


Diagem,
pleases ee remark .. ( bigger than in H&A)

Serg..., I saw that remark...

Leakage is part of the beauty!

Bigger than H&A..., or not!

In step cut stones leakage can become a positive part of the patern creation, along with head obstruction dark zones.
The same can be of some value in crushed ice style radiants and cushions etc.

But for a round diamond - the leakage inside the table area as per Storm''s example - will not be a good contributor to contrast.

It will however be a negative contribution to the wearers pleasure once the stone is dirty - in this case that area will return little light or fire.

re:But for a round diamond - the leakage inside the table area as per Storm''s example - will not be a good contributor to contrast.

Never? Even for stereo-Vision? Even for Fire???

most probably pavilion digit in Rhino sample was 2 degree. Please try 3-3.5 degree and tilt diamond +_5 degree, and compare with same( 41 degree without digit and with digit just 2 degree)

 

[strmrdr]

Date: 11/7/2008 4:57:25 PM
Author: DiaGem
LR = ?

light return.
RB''s have nothing else going for them unlike asschers and emeralds.

 

[diagem]

Date: 11/7/2008 4:55:15 PM
Author: Garry H (Cut Nut)

Date: 11/7/2008 2:55:51 PM
Author: DiaGem

Date: 11/7/2008 2:28:10 PM
Author: Serg

Date: 11/7/2008 2:07:36 PM
Author: DiaGem

Date: 11/7/2008 2:04:03 PM
Author: Serg

Date: 11/7/2008 1:49:43 PM
Author: oldminer
Strmrdr, I see the nice IS images and can readily see they are not identical. However, the burning question is how much difference can the human eye, both the novice and the trained diamond professional see when looking at two such stones? I am certain the IS is a tool which allows us to know there are differences, but I often find some of the differences are nominal in actual, visual appearance. I know we do not have smooth metrics to better define gray areas which are rather broad at the junctions of each cut grade at the present time, so how would you know or show that these two diamonds actually look different from one another to observers?

I don''t believe I have a definitive way to know how differently these two would look. I know I could use direct assessment or probably ray-tracing to give me some numerical results, but still, would I see a difference or would I just wonder if this little bit made a difference? THANKS.

re:would I see a difference or would I just wonder if this little bit made a difference? THANKS.


more questions. If somebody see difference, will he see all times worse appearance for stones with Leakage?? Could stone with leakage ( bigger than in H&A) have better appearance( for example fire is definitely better , but Brilliancy is same) ??? Of course some stones with strong leakage is not nice. But why if Stone has Leakage , its can not be nice? Any proof?

Do you know any cut that has NO leakage at a certain view??? I dont.

reo you know any cut that has NO leakage at a certain view??? I dont.


Diagem,
pleases ee remark .. ( bigger than in H&A)

Serg..., I saw that remark...

Leakage is part of the beauty!

Bigger than H&A..., or not!

In step cut stones leakage can become a positive part of the patern creation, along with head obstruction dark zones.
The same can be of some value in crushed ice style radiants and cushions etc.

But for a round diamond - the leakage inside the table area as per Storm''s example - will not be a good contributor to contrast.

It will however be a negative contribution to the wearers pleasure once the stone is dirty - in this case that area will return little light or fire.

I believe it would depend on the kind of appearance you are either looking for or used (educated) to?

 

[diagem]

Date: 11/7/2008 5:04:59 PM
Author: strmrdr

Date: 11/7/2008 4:57:25 PM
Author: DiaGem
LR = ?

light return.
RB's have nothing else going for them unlike asschers and emeralds.

Why..., what about pattern creation for appearance? isnt that part of the education of H&A's?

ETA: I believe every cut has more things going for it..., not just LR..., contrast and patterns naturally play a more creative role in the fancy cut arena's..., but RB's definitely have play room too!

 

[strmrdr]

Date: 11/7/2008 5:08:42 PM
Author: DiaGem
Why..., what about pattern creation for appearance? isnt that part of the education of H&A''s?

arrows are fleeting and the better the light return the more contrast so they show up better when they do.
This one has nice arrows but they sure don''t stand out.

 

[strmrdr]

Here is the same arrows with only traditional RB leakage....

 

[diagem]

Date: 11/7/2008 5:15:26 PM
Author: strmrdr

Date: 11/7/2008 5:08:42 PM
Author: DiaGem
Why..., what about pattern creation for appearance? isnt that part of the education of H&A''s?

arrows are fleeting and the better the light return the more contrast so they show up better when they do.
This one has nice arrows but they sure don''t stand out.

Exactly..., "part of the education of H&A''s"...

I must admit this pattern is kinda nice..., diiferent than what we are used too..., a bit of character perhaps??

 

[Regular Guy]

Date: 11/7/2008 11:28:46 AM
Author: strmrdr
AGS Gold can not tell these 2 stones apart.

AGS PGS did.

https://www.pricescope.com/community/threads/when-are-is-aset-and-or-reflector-technologies-needed-or-not-needed-for-internet-purchasing%E2%80%A6.99277/

This is what I''m talking about when I say Gold is a shotgun it just shoots a grade out in the general very wide area where PGS is more like a rifle bullet and hits the target in a fairly accurate fashion!

I rest my case, AGS Gold stinks for consumers.

OK, so, as a genuine fan of Occam''s razor, too (i.e., I value less dissonance)...I am again backing Karl here.

Gold may make things easier for cutters...it may get AGS more business...and it may even fill the world with a better class of diamonds for all I know. But...if there is meaning to the sorts of distinctions that science has brought forward on diamond analysis, it''s easy to be a fan of Platinum over gold.

 

[michaelgem]

MYOPIA???

Let's look at simplifications of Ideal round brilliant cut grading, such as those in the Journal Accordance article. This work includes details of commonalities between GIA and AGS charts and tables. Let's look at the use of those charts and tables by GIA and now AGSL to communicate their cut grading systems and grade boundaries. These simplifications, which many believe are essential to understanding and practical utilization, are viewed by some as myopic, over-simplification.

My myopia (near-sightedness) allows me to notices details in small objects like gemstones that often go unnoticed by many. When it comes to diamonds, “cut nuts” or “diamond mavens” notice detail that is often unseen by most in usual diamond viewing. A good example is the subtle leakage and retroflection variations in the middle ring or iris of the “diamond eye” due to slight change in crown or pavilion main angles. These variations occur even within the sweet spot ranges of both AGS and GIA. As several have explained in the past, the effect of these variation's on light performance is exaggerated by their representation in reflector devices, and consequently in the minds of those using them.

The attention to details, such as minor amounts of white leakage in reflector devices, at some level, has little to do with perceived light performance. In the case of slightly steeper and deeper round brilliants, it can explain why many see performance problems, while the GIA and their extensive comparison testing finds them to be EX. Past some point, all agree that steep/deep, just as shallow/shallow, exhibits poor light performance. But as you move from the Ideal combination (41°, 34°, 56%) in the steep/deep direction, the diamond reflects more from wider angles, better avoiding head obstruction. Decreased viewer obstruction explains positive results from observation testing by GIA for slightly steep/deep cuts, carried out in jewelry stores and other usual viewing circumstances. The comparison testing finds slightly steep/deep diamonds, that are just beginning to exhibit middle ring problems, to be judged by most as more, not less, brilliant than even the Tolkowsky Ideal. It appears from this comparison testing that the better perceived brightness of the slightly steep/deep proportions more than compensates for any slight middle ring problems in typical viewing and illumination conditions.

This is a simple explanation of just one example of the differences between what we "mavens" see that most consumers and jewelers in their viewing circumstances may see differently. This understanding causes many of us, myself included, to advocate a tighter sweet spot than either AGS Platinum, Gold or GIA EX. The Journal article noted that I and others “set the bar for the best make higher in some respects than either GIA or AGS.” While this may be fine for the perfectionists among us, if a lab downgrades a diamond cut, whose visual appearance is as good or better than another, in a very real sense, rather than a service, they may be doing a disservice to both the consumer and the cutter.

While acknowledging that my explanations, here and in my article, along with chart representations, like the AGS Gold, may be seen as myopic over simplifications, they are essential for education and understanding by jewelers, gemologist-appraisers, cutters and others in the trade. GIA and now AGS believe they provide a practical and essential way for the cutter to understand and optimize his cut planning. We agree to disagree that nothing material to overall light performance and diamond beauty is being lost or compromised in the use of charts and tables to communicate a cut grading system.

As an example of Occam's razor, charts and tables are the simplest solution for the cutter, jeweler and ultimately the consumer that is adequate and sufficient to the task. GIA has been demonstrating this for over 2 years. The effective use of these charts by Sergey's group to communicate the AGS PGS system and others for his clients is further proof. Sergey's, GIA's and AGS's charts, and for that matter, the Accordance article's explanation of them, are essential rather than myopic simplifications for cut grade understanding and usage by all.

Michael D. Cowing

PS: And I see a greater myopia in those who dismiss or fail to learn from charts like those Sergey's group has generated with the PGS software.

 

[Serg]

Date: 11/7/2008 5:15:26 PM
Author: strmrdr

Date: 11/7/2008 5:08:42 PM
Author: DiaGem
Why..., what about pattern creation for appearance? isnt that part of the education of H&A's?

arrows are fleeting and the better the light return the more contrast so they show up better when they do.
This one has nice arrows but they sure don't stand out.

Karl, please do tilt 5 degree. It will show part of difference between mono view and stereo view.

We are not cyclops

 

[beryl]

QUOTE: 6 Nov, 9:14 AM
"... for Cabochon you need polish Convex facets ..."
Sergey Sivovolenko
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Sorry, I missed this, Sergey. Not important here but needs to be corrected.

There are cabochons with concave facets; they are called 'chevee's. I have made several and written about them (with illustrations) in "Lapidary Journal" circa 1975. The article, called "Falling Stars" showed star concentrated in hollow of star ruby (Linde synthetic). I have done the same with moonstone. I believe I sent a Xerox copy of this article to Yuri Shelementiev circa 2003. I use a hardwood lap embedded with grit or polish in a carver's handpiece spindle (I move stone under lap, Chinese style).

Also, the cylindrical laps I mentioned were about 2 feet (61 cm) diameter, if i recall correctly. I learned of them from DuPont, for whom I was testing their new polycrystalline diamond powder on CZ circa 1976.

 

[Serg]

Date: 11/7/2008 7:10:26 PM
Author: beryl
QUOTE:
''... for Cabochon you need polish Convex facets ...''
Sergey Sivovolenko
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Sorry, I missed this, Sergey. Not important here but needs to be corrected.

There are cabochons with concave facets; they are called ''chevee''s. I have made several and written about them (with illustrations) in ''Lapidary Journal'' circa 1975. The article, called ''Falling Stars'' showed star concentrated in hollow of star ruby (Linde synthetic). I have done the same with moonstone. I believe I sent a Xerox copy of this article to Yuri Shelementiev circa 2003. I use a hardwood lap embedded with grit or polish in a carver''s handpiece spindle (I move stone under lap, Chinese style).

Also, the cylindrical laps I mentioned were about 2 feet (61 cm) diameter, if i recall correctly. I learned of them from DuPont, for whom I was testing their new polycrystalline diamond powder on CZ circa 1976.

Bruce,
re:Sorry, I missed this, Sergey. Not important here but needs to be corrected.There are cabochons with concave facets;

Do you mean There are cabochons without Convex facets?( just flat and concave)? Could you publish here any image?

 

[beryl]

Quote of Sergey 7 Nov, 10:57 AM ................

"Bruce,
Could you please calculate and publish here The correlation between Zones "0" and "Id" on chart had been published by me?
I received 56%-58% level of correlation.
thank you Sergey Sivovolenko"
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Sorry, Sergey; I do not understand what you are asking me to do. When I understand I will try, gladly.

 

[beryl]

QUOTE: 7 Nov, 7:10 PM

"Do you mean There are cabochons without Convex facets?( just flat and concave)? Could you publish here any image? " Sergey Sivovolenko
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Sergey:
Sorry; my scanner not working now to copy article; I will photograph it or a ring I made for my wife - when she finds it. Your description is correct, 'chevee' is flat top cabochon with hollow in it.

EDIT: She just brought me a black jade and lapis-lazuli chevees; I will photograph asap.