Is cut grading science or opinion?

[Karl_K]

Date: 3/11/2010 10:51:13 AM
Author: Paul-Antwerp
This is frustrating.


RD is putting me on trial (kind-of), because he disagrees with my statement:


''GIA''s and AGS''s cut-grade, ASET, IS and HCA are indeed valid techniques, some of them vetted by science, to judge potential brightness most often of a round brilliant only.''


Now, after a lot of word-twisting, everybody is giving opinions aside from the original topic.


Question: If going back to my original question, can anybody disagree? If not, can we agree that this is an undisputable basis?


Live long,

Hi Paul,
I agree with your statement as far as it goes.
I have been staying out of this thread because I refuse to discuss it in this context, it is not fair.

 

[ChunkyCushionLover]

Date: 3/11/2010 9:11:14 AM
Author: Serg

from Oxford dictionary ;
''scientific method
noun
a method of procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.''

from Wiki:

''Scientific method

Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering observable, empirical and measurable evidence subject to specific principles of reasoning.[1] A scientific method consists of the collection of data through observation and experimentation, and the formulation and testing of hypotheses.[2]

Although procedures vary from one field of inquiry to another, identifiable features distinguish scientific inquiry from other methodologies of knowledge. Scientific researchers propose hypotheses as explanations of phenomena, and design experimental studies to test these hypotheses. These steps must be repeatable in order to dependably predict any future results. Theories that encompass wider domains of inquiry may bind many independently-derived hypotheses together in a coherent, supportive structure. This in turn may help form new hypotheses or place groups of hypotheses into context.

Among other facets shared by the various fields of inquiry is the conviction that the process be objective to reduce biased interpretations of the results. Another basic expectation is to document, archive and share all data and methodology so they are available for careful scrutiny by other scientists, thereby allowing other researchers the opportunity to verify results by attempting to reproduce them. This practice, called full disclosure, also allows statistical measures of the reliability of these data to be established.''

For mine opinionDiamond industry has not infrastructure for verification and testing any hypotheses( in Cut grade field). Diamond Science community is to narrow and has not real ability for verification and science discussions. Few articles in science magazines are not science yet. All publications had NOT '' all data and methodology so they are available for careful scrutiny by other scientists, thereby allowing other researchers the opportunity to verify results by attempting to reproduce them''

Most publications were just descriptions ( without any real hypotheses, testing and proof)
Science standards in Diamond industry is very very low because Diamond industry are not interesting to pay for science work. Science is not part Diamond industry.
Again my opinion what Science methods are enemy for most( may be for all)current Diamond business models.
99.9% professionals in diamond industry do not like science approach or can not understand what it is.( if we speak about CutStudy, Grading,..etc)
Science is very expensive Toy for diamond industry yet.

Serg,

Are you the author of any published articles and if so can you provide the links on your website or here?
Are there any published articles relevant to this discussion completed by a member of the Moscow State University Gemological Centre?

Couldn''t find any on the octonus website.

 

[whatmeworry]

My opinion is the science of Cut grading for the "Beauty" of diamonds is incomplete at best. Good luck trying to cut grade the diamonds with plasma etched nano gratings. GIA will not assign a cut grade to them.

And scientific results can be misapplied, particularly if you don''t know the assumptions of those studies and if those assumptions are no longer true. What are some assumptions of those studies? Colorless, no inclusions, perfectly symmetrical, no brillianteering of the girdles, fixed lower girdle length (for HCA), specific lighting environments (IS, ASET, diffusely lit dome), even different definitions for brightness which could differ from that of the end consumer. Since the assumptions may no longer true once you get out into the real world ( add color, inclusions,different consumers with different interpretations of brightness, different lighting environments, etc.), the results may no longer will be true.

As a theoretical example, a black diamond that passes all the tests will not be as bright as a colorless diamond which fails some of the tests. As a real world example, I own a super-ideal H&A from one of the PS vendors. It passes all tests (HCA, IS, ASET, AGS, H&A) yet it is a lower color (J). Yet I perceive it to be less bright (in my office, held at arms length, shaded under the bookcase) than a higher color (E) diamond which fails all the test (HCA, IS, ASET, GIA).

I''m very much in favor of using science to understand and advance diamond beauty. We can use it to advance more choices for the consumers. But it''s incomplete at best and misleading at worst.

Going back to to Paul''s statement.

"GIA''s and AGS''s cut-grade, ASET, IS and HCA are indeed valid techniques, some of them vetted by science, to judge potential brightness most often of a round brilliant only."

I agree with this, but in the real world "your mileage may vary". http://en.wiktionary.org/wiki/your_mileage_may_vary

 

[Rockdiamond]

Date: 3/11/2010 10:51:13 AM
Author: Paul-Antwerp
This is frustrating.


RD is putting me on trial (kind-of), because he disagrees with my statement:


''GIA''s and AGS''s cut-grade, ASET, IS and HCA are indeed valid techniques, some of them vetted by science, to judge potential brightness most often of a round brilliant only.''


Now, after a lot of word-twisting, everybody is giving opinions aside from the original topic.


Question: If going back to my original question, can anybody disagree? If not, can we agree that this is an undisputable basis?


Live long,

Paul- my sincere apologies- it was never my intent to put anyone on trial- nor to twist anyone''s words.
I have the utmost respect for you, therefore when this subject has come up in the past, I was the one who felt a bit slighted in that we never seemed to be able to tackle a few specific points that I feel are germain to PS specifically, and diamonds in general.
Your credentials put your input on a different level than many people posting.

Instead of using your words, please allow me to try and paraphrase my impression of your statements:
If someone refuses to accept the use of ASET/IS HCA to grade the cut ( although your latest statements use the term "brilliance" instead of cut), then they refuse to accept science, and are stuck thinking in "old ways"

Now that we have substituted the word "brilliance" for cut, can we agree that many here on PS feel that brilliance, as observed by ASET/IS HCA is thought to be "desirable"?
If we agree on that, then we can infer that stones observed to have less brilliance using ASET/IS/HCA are "scientifically" deficient to stones observed to be more brilliant.

It was never my point that there''s anything "wrong" with perfect optical symmetry- just that there''s also nothing inherently "right" about it if the question is desirability of cut.
It''s a question of taste.

 

[oldminer]

You have to delve into what the word "cut grading" means when it comes to diamonds. I am not fixed on any particular choice as there are many ways to approach what cut grading really is.

One group wants numerical measurements of the perfection of symmetry and polish. Also, the numerical perfection of parameters such as diameter variation percentage, or consistency of girdle thickness. A number of folks here might want repeatable measurements of light return, scintillation, contrast or fire. While we may not want them ourselves, these things can be accomplished in a manner that is scientific. HOWEVER, these things are not automatically the equivalent of measuring or assigning a beauty grade. These things are for people who are driven by numbers and factual data. That''s fine, but it is not the total picture of a diamond''s cut or beauty.

On the far opposite side are those who just want beauty. They have in their mind''s eye an undefined need to obtain a diamond which they personally feel has beauty, an appearance whcih greatly pleases them. They may not care one bit about a scientific approach or a cut grade.

In the middle are the majority who want good value, a very good looking diamond, a diamond which looks rather normal rather than unusual, one that is large enough, good enough, the right shape, and fits their budget. They will take some science in the appraoch, but it usually must be spoon fed and too much spoon feeding usually has the result of choking someone before they can swallow. So, we have to soft peddle the science and encourage a bit of the romantic, personal beauty aspect, too. I think this is a good balance, but it does not fit the upper or lower level of consumers mentioned above that are on the far right or far left (of romance or science, not politics).

The results of science are translated to consumers via educated, expert opinions given by individuals. Very few consumers go to source material, but prefer to gain knowledge from interaction with appraisers and vendors. So, you have opinions mixed with whatever level of science there may be. Everyone has a different take on the mix and opinions do vary. The pure science behind the scenes is not a variable, but the way it is expressed to consumers has a far greater range of variance.

Anyone who says the measurements, light or parametric, provide all there is to know about diamond beauty is not providing accurate information. Scientific facts can make a compelling case in some instances, but the judgment of beauty remains personal and not what science should be attempting to do. Opinions are key to beauty. Opinions may be based on science to some extent and this is why we use science more for screening than selecting the final stone. The final stone selected ought to be based on a personal opinion and may consider scientific evidence in forming that opinion, but the ultimate choice should be opinion based and dependent on the individual who makes the decision.

 

[Rockdiamond]

Now Dave, when an appraiser who promotes cut grades charts makes these arguments, it smacks of self interest....sorry, but turnaoround is fair play ( see page one)

The results of science are translated to consumers via educated, expert opinions given by individuals

Seriously- the above statement is rally at the meat of this discussion.
If an ASET indicates something, is it scientific to assess a value of quality of cut based on that result?

Two diamonds with identical measurements can look different.
It might be different LGF lengths- or different corner size in fancy shapes- but the net result is that "scientific analysis" can not be used to judge a diamond''s beauty , or quality of cut, based on measurements alone.
At some point an subjective assessment must be made.
GIA cut grades are, to some extent subjective, in that human observation is incorporated into the cut grading system.

 

[Lorelei]

Date: 3/11/2010 1:25:54 PM
Author: oldminer
You have to delve into what the word ''cut grading'' means when it comes to diamonds. I am not fixed on any particular choice as there are many ways to approach what cut grading really is.

One group wants numerical measurements of the perfection of symmetry and polish. Also, the numerical perfection of parameters such as diameter variation percentage, or consistency of girdle thickness. A number of folks here might want repeatable measurements of light return, scintillation, contrast or fire. While we may not want them ourselves, these things can be accomplished in a manner that is scientific. HOWEVER, these things are not automatically the equivalent of measuring or assigning a beauty grade. These things are for people who are driven by numbers and factual data. That''s fine, but it is not the total picture of a diamond''s cut or beauty.

On the far opposite side are those who just want beauty. They have in their mind''s eye an undefined need to obtain a diamond which they personally feel has beauty, an appearance whcih greatly pleases them. They may not care one bit about a scientific approach or a cut grade.

In the middle are the majority who want good value, a very good looking diamond, a diamond which looks rather normal rather than unusual, one that is large enough, good enough, the right shape, and fits their budget. They will take some science in the appraoch, but it usually must be spoon fed and too much spoon feeding usually has the result of choking someone before they can swallow. So, we have to soft peddle the science and encourage a bit of the romantic, personal beauty aspect, too. I think this is a good balance, but it does not fit the upper or lower level of consumers mentioned above that are on the far right or far left (of romance or science, not politics).

The results of science are translated to consumers via educated, expert opinions given by individuals. Very few consumers go to source material, but prefer to gain knowledge from interaction with appraisers and vendors. So, you have opinions mixed with whatever level of science there may be. Everyone has a different take on the mix and opinions do vary. The pure science behind the scenes is not a variable, but the way it is expressed to consumers has a far greater range of variance.

Anyone who says the measurements, light or parametric, provide all there is to know about diamond beauty is not providing accurate information. Scientific facts can make a compelling case in some instances, but the judgment of beauty remains personal and not what science should be attempting to do. Opinions are key to beauty. Opinions may be based on science to some extent and this is why we use science more for screening than selecting the final stone. The final stone selected ought to be based on a personal opinion and may consider scientific evidence in forming that opinion, but the ultimate choice should be opinion based and dependent on the individual who makes the decision.

Brilliant post! And that is what we are trying to do is cater for everyone according to their individual needs and preferences. Not everyone wants to buy the same thing or is looking for the same level of cut quality, if this was the case then it would be easy!

 

[Michael_E]

Date: 3/11/2010 12:55:48 PM
Author: whatmeworry

I''m very much in favor of using science to understand and advance diamond beauty. We can use it to advance more choices for the consumers. But it''s incomplete at best and misleading at worst.

I think that the problem is in the question. There is a science of optics, which for our purposes, is perfectly well understood. Then there is the objective problem of grading something as nebulous as "beauty" and trying to assign levels to it. This attempt to grade beauty might be successful, if everyone would agree on just what the exact parameters surrounding the grading of beauty are...but as we all know that will never happen. Using science as the objective tool that it is, is fine. Trying to use science to define something as subjective as "beauty" is a bit like mixing oil and water...it''s not going to happen. If a person will define the parameters of beauty for themselves and THEN use the tools of science to obtain those stones which maximize their preferred parameters, then this idea of using science all makes sense and will work well.

The ASET tool for instance, is a tool designed to show a person where the light is coming from, ( or not coming from), relative to the horizon of the crown of a diamond, (or any other cut gem for that matter). Pretty simple. The science behind it is that the brightness of light related to our personal world horizon is such that it''s brightest directly overhead and tapers off in intensity as the altitude decreases. If the world horizon and the horizon of the diamond are close, (holding the diamond with the table pointing vertically), then the view of reflected light from the diamond will match what one assumes they will see based on the ASET device. Once you start viewing the diamond at an angle, tilting it in relation to the horizon, or trying to get information about other aspects of a diamonds performance, the usefulness of the ASET tool is limited and you need to find some other science based system to gather the information that you seek, (assuming that you want to quantify your parameters and requirements). Science based tools work very well...as long as you can define what you are looking for, you know how the tools work and what limitations they possess.

 

[Serg]

Date: 3/11/2010 11:17:49 AM
Author: ChunkyCushionLover

Date: 3/11/2010 9:11:14 AM

Author: Serg


from Oxford dictionary ;

''scientific method

noun

a method of procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses.''

from Wiki:

''Scientific method

Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering observable, empirical and measurable evidence subject to specific principles of reasoning.[1] A scientific method consists of the collection of data through observation and experimentation, and the formulation and testing of hypotheses.[2]

Although procedures vary from one field of inquiry to another, identifiable features distinguish scientific inquiry from other methodologies of knowledge. Scientific researchers propose hypotheses as explanations of phenomena, and design experimental studies to test these hypotheses. These steps must be repeatable in order to dependably predict any future results. Theories that encompass wider domains of inquiry may bind many independently-derived hypotheses together in a coherent, supportive structure. This in turn may help form new hypotheses or place groups of hypotheses into context.

Among other facets shared by the various fields of inquiry is the conviction that the process be objective to reduce biased interpretations of the results. Another basic expectation is to document, archive and share all data and methodology so they are available for careful scrutiny by other scientists, thereby allowing other researchers the opportunity to verify results by attempting to reproduce them. This practice, called full disclosure, also allows statistical measures of the reliability of these data to be established.''


For mine opinionDiamond industry has not infrastructure for verification and testing any hypotheses( in Cut grade field). Diamond Science community is to narrow and has not real ability for verification and science discussions. Few articles in science magazines are not science yet. All publications had NOT '' all data and methodology so they are available for careful scrutiny by other scientists, thereby allowing other researchers the opportunity to verify results by attempting to reproduce them''


Most publications were just descriptions ( without any real hypotheses, testing and proof)

Science standards in Diamond industry is very very low because Diamond industry are not interesting to pay for science work. Science is not part Diamond industry.

Again my opinion what Science methods are enemy for most( may be for all)current Diamond business models.

99.9% professionals in diamond industry do not like science approach or can not understand what it is.( if we speak about CutStudy, Grading,..etc)

Science is very expensive Toy for diamond industry yet.

Serg,


Are you the author of any published articles and if so can you provide the links on your website or here?

Are there any published articles relevant to this discussion completed by a member of the Moscow State University Gemological Centre?


Couldn''t find any on the octonus website.

CCL,

did you check page :
http://www.octonus.com/oct/projects/

?

 

[Texas Leaguer]

Date: 3/11/2010 10:51:13 AM
Author: Paul-Antwerp
This is frustrating.

RD is putting me on trial (kind-of), because he disagrees with my statement:

'GIA's and AGS's cut-grade, ASET, IS and HCA are indeed valid techniques, some of them vetted by science, to judge potential brightness most often of a round brilliant only.'

Now, after a lot of word-twisting, everybody is giving opinions aside from the original topic.

Question: If going back to my original question, can anybody disagree? If not, can we agree that this is an undisputable basis?

Live long,

Paul, I don’t see how anyone can disagree with that basic statement unless they are determined to be in a slugfest, which may be part of the purpose. At least it serves to get juices flowing and stimulate some exchange of ideas that can then stand on their own merits. But returning to the original subject line of the thread (is cut grading science or opinion?) I think Cara really nailed it with the succinct “Yes” posting, and others have elaborated.

The most respected labs offering cut grading have systems based upon science that strive to distill facts into an interpretive framework that will be helpful to the consumer in making decisions based upon their own personal priorities. Ray tracing software programs that run millions of mathematical calculations based upon the laws of physics, is surely science. Reflector devices that reveal information about how a particular stone is handling light are certainly valid tools for deriving relevant information. And lastly there is an interpretational element about how that science may translate into certain aspects of beauty.

It can certainly be argued that some grading systems are based upon “better” science than others, and that some tools give better insight than others or correlate more closely to widely held concepts of beauty. If there is such a thing as social science, and we can agree that it is actual science, then one fact is certain: not everyone likes the same things! Some folks find highly detailed and realistic paintings the most beautiful. They may not relate at all to abstract works of art that others are completely transported by.

The various tools, techniques and technologies that we have today and which will be developed tomorrow give us more predictability in producing or finding what we really want. In the realm of aesthetics one size will never fit all. Even with the best science we will never be able to prove that one specific information set will necessarily be preferred by everyone. However, there are general preferences in the population that can be understood, which brings us back to the realm of social science and the role of branding and marketing.

 

[ChunkyCushionLover]

http://www.agslab.com/spie/spie_lo_res.pdf paper above is a well written article at the heart of what we are discussing here.

From my scientific background (8 years in postgraduate research) I recognize that The Journal of Optical Engineering while not of the highest impact factor (more middle tier) in optics certainly qualifies as a more than reasonable standard with suitable referees and scrutiny.

Very easily, cut grading and how it relates to light performance is well supported by academic research and the use of scientific methodologies.

Unfortunately for the gem industry as a whole the work of AGS labs may not advance as quickly as other pure science topics, because innovators are commercially motivated to submit patents and/or communicate privately rather than submit their findings to public journals.

Once one gets passed the basic argument that light performance which can be quantified is not equivalent to the subjective judgement of beauty but is instead one of the fundamental components of beauty in diamonds, I can't see how anyone can question the science behind the cut grading systems.

 

[Rockdiamond]

Date: 3/11/2010 1:53:21 PM
Author: Michael_E

Date: 3/11/2010 12:55:48 PM

Author: whatmeworry

I'm very much in favor of using science to understand and advance diamond beauty. We can use it to advance more choices for the consumers. But it's incomplete at best and misleading at worst.

I think that the problem is in the question. There is a science of optics, which for our purposes, is perfectly well understood. Then there is the objective problem of grading something as nebulous as 'beauty' and trying to assign levels to it. This attempt to grade beauty might be successful, if everyone would agree on just what the exact parameters surrounding the grading of beauty are...but as we all know that will never happen. Using science as the objective tool that it is, is fine. Trying to use science to define something as subjective as 'beauty' is a bit like mixing oil and water...it's not going to happen. If a person will define the parameters of beauty for themselves and THEN use the tools of science to obtain those stones which maximize their preferred parameters, then this idea of using science all makes sense and will work well.


The ASET tool for instance, is a tool designed to show a person where the light is coming from, ( or not coming from), relative to the horizon of the crown of a diamond, (or any other cut gem for that matter). Pretty simple. The science behind it is that the brightness of light related to our personal world horizon is such that it's brightest directly overhead and tapers off in intensity as the altitude decreases. If the world horizon and the horizon of the diamond are close, (holding the diamond with the table pointing vertically), then the view of reflected light from the diamond will match what one assumes they will see based on the ASET device. Once you start viewing the diamond at an angle, tilting it in relation to the horizon, or trying to get information about other aspects of a diamonds performance, the usefulness of the ASET tool is limited and you need to find some other science based system to gather the information that you seek, (assuming that you want to quantify your parameters and requirements). Science based tools work very well...as long as you can define what you are looking for, you know how the tools work and what limitations they possess.

Great post Michael- hits the nail right on the head.
An ASET works great, but the information provided might not necessarily be relevant to the question at hand. At worst it might be very misleading.
Yet many here insist on using terms like "performance" to describe a diamond.

Texasleaguer, I might have read this wrong, but I think Cara's post was funny- written tongue in cheek.

I will add that I'm not interested in a "slugfest"- but I have felt moved on many occasions to question certain statements made here.
Not to argue, although if opinions are held strongly, that might be a result.
Also a very good reason to continue the dialog.

 

[Texas Leaguer]

Date: 3/11/2010 3:05:17 PM
Author: ChunkyCushionLover

http://www.agslab.com/spie/spie_lo_res.pdf paper above is a well written article at the heart of what we are discussing here.

From my scientific background (8 years in postgraduate research) I recognize that The Journal of Optical Engineering while not of the highest impact factor (more middle tier) in optics certainly qualifies as a more than reasonable standard with suitable referees and scrutiny.

Very easily, cut grading and how it relates to light performance is well supported by academic research and the use of scientific methodologies.

Unfortunately for the gem industry as a whole the work of AGS labs may not advance as quickly as other pure science topics, because innovators are commercially motivated to submit patents and/or communicate privately rather than submit their findings to public journals.

Once one gets passed the basic argument that light performance which can be quantified is not equivalent to the subjective judgement of beauty but is instead one of the fundamental components of beauty in diamonds, I can''t see how anyone can question the science behind the cut grading systems.

Good points. It should be understood that gem labs are commercial entities and as such are not pure scientific enterprises. Like any business they must accomodate the interests of the market segment that are targeting. This has an impact on the way they apply the science that they have developed. A large lab like GIA has a very broad base to accomodate, while a lab like AGS can be more focussed in their mission. This will have a bearing on the value aspects of their work product. There are valid reasons why customers may prefer one lab over another, which may or may not be related to the purity of the scientific work upon which the systems are based.

 

[Regular Guy]

Date: 3/11/2010 3:05:17 PM
Author: ChunkyCushionLover

http://www.agslab.com/spie/spie_lo_res.pdf paper above is a well written article at the heart of what we are discussing here.

CCL, I''m guessing this is not the link you intended...which redirects you, and takes you to a general AGS page...was it?

 

[ChunkyCushionLover]

Date: 3/11/2010 9:55:50 PM
Author: Regular Guy

Date: 3/11/2010 3:05:17 PM
Author: ChunkyCushionLover

http://www.agslab.com/spie/spie_lo_res.pdf paper above is a well written article at the heart of what we are discussing here.

CCL, I''m guessing this is not the link you intended...which redirects you, and takes you to a general AGS page...was it?

Pricescope forum garbled the link the spaces are underscores and no space at the end. I''m not sure I can post the link so its clickable AGS Paper. Maybe this will work.

 

[Regular Guy]

CCL, good work, and good for you. I had actually been looking for the same reference (whether or not it makes the point) without success.

Many thanks,

 

[kenny]

Oh CCL, thanks for that cool AGS pdf file.
I can't wait to read it.

Good science in my opinion.

 

[diagem]

Date: 3/12/2010 12:18:53 AM
Author: ChunkyCushionLover

Date: 3/11/2010 9:55:50 PM
Author: Regular Guy

Date: 3/11/2010 3:05:17 PM
Author: ChunkyCushionLover

http://www.agslab.com/spie/spie_lo_res.pdf paper above is a well written article at the heart of what we are discussing here.

CCL, I''m guessing this is not the link you intended...which redirects you, and takes you to a general AGS page...was it?

Pricescope forum garbled the link the spaces are underscores and no space at the end. I''m not sure I can post the link so its clickable AGS Paper. Maybe this will work.

I must admit this work got me all curious & was one the reasons that got me starting cutting (some) real Diamonds according to reflector technologies.
I remember I had the urge to cut and compare real life results vs. virtual (DC) results.

Great read for anyone who wants to learn more deeply into the subject.

 

[Paul-Antwerp]

Date: 3/11/2010 12:55:48 PM
Author: whatmeworry


My opinion is the science of Cut grading for the ''Beauty'' of diamonds is incomplete at best. Good luck trying to cut grade the diamonds with plasma etched nano gratings. GIA will not assign a cut grade to them.
And scientific results can be misapplied, particularly if you don''t know the assumptions of those studies and if those assumptions are no longer true. What are some assumptions of those studies? Colorless, no inclusions, perfectly symmetrical, no brillianteering of the girdles, fixed lower girdle length (for HCA), specific lighting environments (IS, ASET, diffusely lit dome), even different definitions for brightness which could differ from that of the end consumer. Since the assumptions may no longer true once you get out into the real world ( add color, inclusions,different consumers with different interpretations of brightness, different lighting environments, etc.), the results may no longer will be true.

As a theoretical example, a black diamond that passes all the tests will not be as bright as a colorless diamond which fails some of the tests. As a real world example, I own a super-ideal H&A from one of the PS vendors. It passes all tests (HCA, IS, ASET, AGS, H&A) yet it is a lower color (J). Yet I perceive it to be less bright (in my office, held at arms length, shaded under the bookcase) than a higher color (E) diamond which fails all the test (HCA, IS, ASET, GIA).

I''m very much in favor of using science to understand and advance diamond beauty. We can use it to advance more choices for the consumers. But it''s incomplete at best and misleading at worst.

Going back to to Paul''s statement.

''GIA''s and AGS''s cut-grade, ASET, IS and HCA are indeed valid techniques, some of them vetted by science, to judge potential brightness most often of a round brilliant only.''

I agree with this, but in the real world ''your mileage may vary''. http://en.wiktionary.org/wiki/your_mileage_may_vary

Mileage may vary, I agree with that. That is why all these tests are rejection-tests.

Live long

 

[Paul-Antwerp]

Date: 3/11/2010 1:11:57 PM
Author: Rockdiamond

Date: 3/11/2010 10:51:13 AM
Author: Paul-Antwerp
This is frustrating.

RD is putting me on trial (kind-of), because he disagrees with my statement:

''GIA''s and AGS''s cut-grade, ASET, IS and HCA are indeed valid techniques, some of them vetted by science, to judge potential brightness most often of a round brilliant only.''

Now, after a lot of word-twisting, everybody is giving opinions aside from the original topic.

Question: If going back to my original question, can anybody disagree? If not, can we agree that this is an undisputable basis?

Live long,

Paul- my sincere apologies- it was never my intent to put anyone on trial- nor to twist anyone''s words.
I have the utmost respect for you, therefore when this subject has come up in the past, I was the one who felt a bit slighted in that we never seemed to be able to tackle a few specific points that I feel are germain to PS specifically, and diamonds in general.
Your credentials put your input on a different level than many people posting.

Instead of using your words, please allow me to try and paraphrase my impression of your statements:
If someone refuses to accept the use of ASET/IS HCA to grade the cut ( although your latest statements use the term ''brilliance'' instead of cut), then they refuse to accept science, and are stuck thinking in ''old ways''

Now that we have substituted the word ''brilliance'' for cut, can we agree that many here on PS feel that brilliance, as observed by ASET/IS HCA is thought to be ''desirable''?
If we agree on that, then we can infer that stones observed to have less brilliance using ASET/IS/HCA are ''scientifically'' deficient to stones observed to be more brilliant.

It was never my point that there''s anything ''wrong'' with perfect optical symmetry- just that there''s also nothing inherently ''right'' about it if the question is desirability of cut.
It''s a question of taste.

So, David,

You apologize for twisting my words, and then you immediately do it again?

 

[kenny]

Round and round and round we go.

 

[Serg]

Date: 3/12/2010 11:38:21 AM
Author: kenny
Round and round and round we go.

Hi Kenny,
You are right ?
Could we discuss about conditions when science in Cut grade( Beauty Grade) could profitable for Diamond industry?

 

[oldminer]

If you seek "IDEAL" in a fancy shape, you will NEVER select an 80% deep Princess cut over one with 65% depth, and in round brilliants you would never select one with 63% depth or more, provided the stones being examined for purchase all have equal light return and brilliancy.

The fancy one with 65% depth or the round with less than 63% depth will be SUPERIOR then, simply because they look larger than deeper stones. An overly deep stone may be a great light performer, but it falls down on the apparent size issue. This means it could NEVER BE IDEAL, if something BETTER equals its light performance and also has a better attribute, namely apparent size.

You can readily select the finest POTENTIAL cut by numbers and parameters. Right now you cannot predict which ones will give the very finest light return, but you can eliminate all the stones that will be too thin, too thick, not durable or ugly in length-to-width ratio. This is not an imaginary benefit that was dreamed up somewhere, but comes from years of grading diamonds and being interested in what other experts want and expect from the finest fancy shapes. An ugly fancy will NEVER be an IDEAL. A very deep fancy will never be a true IDEAL. A fragile stone will never be IDEAL. Too deep a stone, no matter how brilliant, is not IDEAL, Too thin a stone, no matter how large or accidentally brilliant, will never be IDEAL. There are people who do not choose to buy Ideal cut diamonds. It is up to each one of us to judge if a diamond is ugly, beautiful or somewhere in between. Calling it "Ideal" does not mean it is the only stone to consider buying.

IDEAL is the ULTIMATE, not simply due to a performance based on brilliancy. While brilliancy alone may be the way the general industry would like to grade fancy shapes and/or rounds, so that any diamond, no matter how poorly cut, is "IDEAL" as long as it is highly brilliant, this is a foolish notion. This approach would favor cutters and dealers at the expense of integrity and punish those few consumers who still have some degree of faith in diamond sellers.

IDEAL is an absolute concept of TOP QUALITY light return and cutting, and it ought to be seen as encompassing all the aspects of each stone so judged. Anything less is not really an unqualified Ideal cut. Individual consumers can buy based on their own concept of beauty, price, or any other set of parameters they choose, but only a limited number of diamonds deserve to be called “Ideal Cut” as they are near perfect in technical as well as performance specs.

The AGA Cut Class grades and the HCA for rounds provide the shape information that one adds to brilliancy information. This brilliancy information can be from Ideal-Scopes used with round diamonds, the ASET Scope and from tools such as Gemex, ImaGem or Isee2. The parametric and performance information is also part of the AGS system grading structure. This combination of expert knowledge, technical data, and science gives today’s dealers and consumers the currently best tools and information to judge or grade a diamond as “IDEAL“. No doubt we will see further technological scientific advancement in grading in years to come. I predict grading of diamonds, including cut grading, will continue to become more of a science based structure than it is today and that the trade will argue about it for many years to come. Progress or change always creates controversy.

 

[Stephan]

David (oldminer),

What do you think about following diamond?
http://www.jamesallen.com/diamonds/I-SI2-Ideal-Cut-Round-Diamond-1266629.asp
Your chart says it is a 2A class diamond.
AGS says it''s ideal.

Why does this diamond score so low on your chart?
What bad effect should we expect?

Thank you!

 

[risingsun]

Date: 3/12/2010 12:18:53 AM
Author: ChunkyCushionLover

Date: 3/11/2010 9:55:50 PM
Author: Regular Guy

Date: 3/11/2010 3:05:17 PM
Author: ChunkyCushionLover

http://www.agslab.com/spie/spie_lo_res.pdf paper above is a well written article at the heart of what we are discussing here.

CCL, I''m guessing this is not the link you intended...which redirects you, and takes you to a general AGS page...was it?

Pricescope forum garbled the link the spaces are underscores and no space at the end. I''m not sure I can post the link so its clickable AGS Paper. Maybe this will work.

Excellent article, CCL. Thanks for posting.

 

[risingsun]

Date: 3/12/2010 12:51:35 PM
Author: oldminer
If you seek 'IDEAL' in a fancy shape, you will NEVER select an 80% deep Princess cut over one with 65% depth, and in round brilliants you would never select one with 63% depth or more, provided the stones being examined for purchase all have equal light return and brilliancy.

The fancy one with 65% depth or the round with less than 63% depth will be SUPERIOR then, simply because they look larger than deeper stones. An overly deep stone may be a great light performer, but it falls down on the apparent size issue. This means it could NEVER BE IDEAL, if something BETTER equals its light performance and also has a better attribute, namely apparent size.

You can readily select the finest POTENTIAL cut by numbers and parameters. Right now you cannot predict which ones will give the very finest light return, but you can eliminate all the stones that will be too thin, too thick, not durable or ugly in length-to-width ratio. This is not an imaginary benefit that was dreamed up somewhere, but comes from years of grading diamonds and being interested in what other experts want and expect from the finest fancy shapes. An ugly fancy will NEVER be an IDEAL. A very deep fancy will never be a true IDEAL. A fragile stone will never be IDEAL. Too deep a stone, no matter how brilliant, is not IDEAL, Too thin a stone, no matter how large or accidentally brilliant, will never be IDEAL. There are people who do not choose to buy Ideal cut diamonds. It is up to each one of us to judge if a diamond is ugly, beautiful or somewhere in between. Calling it 'Ideal' does not mean it is the only stone to consider buying.

IDEAL is the ULTIMATE, not simply due to a performance based on brilliancy. While brilliancy alone may be the way the general industry would like to grade fancy shapes and/or rounds, so that any diamond, no matter how poorly cut, is 'IDEAL' as long as it is highly brilliant, this is a foolish notion. This approach would favor cutters and dealers at the expense of integrity and punish those few consumers who still have some degree of faith in diamond sellers.

IDEAL is an absolute concept of TOP QUALITY light return and cutting, and it ought to be seen as encompassing all the aspects of each stone so judged. Anything less is not really an unqualified Ideal cut. Individual consumers can buy based on their own concept of beauty, price, or any other set of parameters they choose, but only a limited number of diamonds deserve to be called “Ideal Cut” as they are near perfect in technical as well as performance specs.

The AGA Cut Class grades and the HCA for rounds provide the shape information that one adds to brilliancy information. This brilliancy information can be from Ideal-Scopes used with round diamonds, the ASET Scope and from tools such as Gemex, ImaGem or Isee2. The parametric and performance information is also part of the AGS system grading structure. This combination of expert knowledge, technical data, and science gives today’s dealers and consumers the currently best tools and information to judge or grade a diamond as “IDEAL“. No doubt we will see further technological scientific advancement in grading in years to come. I predict grading of diamonds, including cut grading, will continue to become more of a science based structure than it is today and that the trade will argue about it for many years to come. Progress or change always creates controversy.

This is a cogent description, in my opinion, of how to view Ideal graded stones. To dispute that the science doesn't exist does not make any logical sense. It does exist and we have evidence to back this up. When I compare my super ideal diamonds to my other diamonds, there is a significant difference. Some may call this subjective, but other people have observed the difference, too. I've compared super ideals with numerous RB stones, which have been less precisely cut. They do not look the same. I do not consider this a coincidence. The consumer should be educated and then make whatever choice suits his/her preferences.

 

[joxxxelyn]

Science or not, as a consumer I can see the difference with my eyes between diamonds that measure really well on these tools and diamonds that do not. Therefore, I don''t think being scientific is the question, but whether consumers find the tool useful (and vendors, for that matter).

 

[oldminer]

"David (oldminer),

What do you think about following diamond?
http://www.jamesallen.com/diamonds/I-SI2-Ideal-Cut-Round-Diamond-1266629.asp
Your chart says it is a 2A class diamond.
AGS says it''s ideal.
Why does this diamond score so low on your chart?
What bad effect should we expect?
Stephan"

I have copied a screen shot from the automated grader which uses the "RULES" that are to be applied to the AGA Cut Class system. Many people mistakenly use the charts and ignore how to compute a final grade. This diamond grades 1B and it has a somewhat shallow crown angle. Still 1B is within AGS0 nearly all the time.

 

[Stephan]

Thank you David!
What does this shallow crown imply?

 

[oldminer]

As the crown angle decreases below the Tolkowsky 34.5 into lower angles, the durability of the girdle edge becomes reduced, but not very much, until about 30 degrees or less. So, as one heads lower, the level of "perfection" as I judge it begins to diminish. It does not happen all at once, but it is a gradual level of degradation which I have used. Thiis diamond may be lovely and the grade is certainly a very good overall grade, but because consumers want to have consistent expert opinions and I wanted to provide them with this consistency, the automated grader did the entire job and repeats itself as we hope it would.

Using the AGA Cut Class charts without regard to the published rules of use or not filling in the entire set of blanks in the auto grader leaves one to guess about the final grade and many times the guess proves incorrect.