Why did GIA included Steep Deep diamonds in ''Excellent''

[Garry H (Cut Nut)]

Date: 8/12/2005 7:41:50 AM
Author: adamasgem

Date: 8/11/2005 3:51:22 AM
Author: Garry H (Cut Nut)

Date: 8/10/2005 11:50:46 AM
Author: adamasgem
RE: Gary Holloway: . Have you seen Sergey''s spoon test? do this - carry a spoon with you from room to room (you will have to be awake during the day Marty and i am not sure if that is feasible - so you could ask someone else to do this test ). put the spon upside down at desk top / table top and see the difference between light intensity from windows and ceiling lights - amazingly fluoro lights are not as intense as light from windows - only very bright halogens are more intense - but have much less light - but they contribute to fire because they are smallish point sources.

In one case you diffuse and in the other you concentrate light
the point is that the light from the window is often more diffused but also more intense

I don''t think that consumers give a rats rearend how their diamonds look to strangers in a supermarket, but that is only my opinion..

I am not surprised that you think that, but then you are not exactly the diamontaaires target demographic - diamonds do not sparkle in the dark - especially when they are locked in the coffin

I have not made my mind up yet that GIA''s gray tray is good or bad. But i can see that there is no need to now think (as Paul from antwerp has feared) that there is some conspiracy theory at work - because if you tested diamonds on a light enough gray tray then clean leaky stones in bright lighting will look great. And that means the old AGS Steep Deeps that we all contributed to down grading of, could have been better performing stones than we all came to believe.

Is the object of the exercise to objectively evaluate the quantity and quality a diamond''s light return when light enters the crown or when attenuated light (both in intensity and spectrum) enters from below the girdle plane. Exactly

So again folks - thi is I believe time for us to make some serious re-analysis of all our assumptions.

Is it valid that some light, or enough light enters the pavilion on pieces of worn jewellry in various settings to make GIA''s results valid?

It appears to me that the common viewing environment and the theoretical studies presented are inconsistent there is no doubt in my mind they threw the theoretical computer based ray trace studies in the trash can - especially after some of Ilene Reinitz''s comments in question time 2 or 3 years back at the JCK "watch this place" song and dance routine.

The main question here is - how many diamonds are set so light can get in the back?

I think 99% of earrings and pendants should be modelled on black trays. And my own experiment with Drena''s earrings with one shallow vs one ''ideal'' cut stone in each ear clearly showed that shallower stones make much better earrings when worn and when they have a bit of normal dirt on them. (A number of people observed this test in Vegas this year and all agreed. I conducted the test over about 6 months, and as a reward Drena went from 1ct to 1 1/4ct each ear

). But then again, aren''t you a bit biased towrd shallower stones

like you are biased toward symmetry - you use toys and I use simple experiance

Now as for rings - say 66%??? are set in 4 or 6 prong settings and can get some light in the pavilion. Reasonable?
Is a say 50% gray tray a reasonable test? It is more reasonable than 100% intensity from the side
Does dirt make this better or worse? Grease, as in body oils, not ''dirt'' per se How should we define "oils" Sol? RI? Colour spectrum / absorption etc?
More applicable or less?

 

[strmrdr]

Date: 8/12/2005 7:47:14 AM
Author: adamasgem

Date: 8/10/2005 1:18:51 PM

Author: strmrdr

This is fairly typical of ''white'' leds and what Marty is talkin about with them.

Thanks for posting it. The LED color temperature distribution is VERY different than the D65 spectrum used in the GIA fire article

Welcome.
Do you have a similar chart for a good D65 source?
I cant find one online.

 

[strmrdr]

spoke too soon, I found this one but dont know how accurate it is.

 

[oldminer]

Wow, what a technical article for Pricescope. A lot of good thought is being shared. THANK YOU.

I think the matter is simpler than technical. It is a marketing strategy, possibly based on some flawed "research" or even possibly on a degree of satisfactory research, that the decision was taken by GIA to offer a very wide range of "Excellent" rather than a more carefully crafted one that discriminates with a finer set of parameters or measures.

Folks who have long resisted grading the cut will probably prefer GIA's version of cut grading to more stringent systems. This will mean that other systems such as AGS, GCAL, Gemex, Ogi, Sarin, Drucker or ImaGem, will be more useful to Internet vendors and high end B&M retailers, than the GIA system. The 95% to 98% majority of consumers don't care so much about absolute performance anyway, but buy more on impulse and budget constraints. The GIA system may suit this large majority of people better than any narrower, more discerning system. This is good for a lab's bottom line, but it may not be the best technical method for discriminating performance levels and beauty.

People are going to want to know about the success of light performance in fancy shapes, too. It appears the GIA is not going forward on that front, but just sticking to rounds. One could say our leader is letting us down a little. One might also say we are being freed to follow our own path in creating standards. Neither is a perfect situation, but I prefer freedom instead of mindlessly following a sadly now questionable "market leader".

Maybe someday all of us who intend to MEASURE light performance will get together in a secret location and work out our relatively small differences. There should or could be a universal "Standard". I'd like to tell consumers we use a "standard methodology". I would give credence to the reports we do, and would give some power to labs that are trying to make a real difference. Meanwhile, the debate and sharing is all useful to have on the forum to read and compare.

 

[adamasgem]

Date: 8/12/2005 8:50:31 AM
Author: Garry H (Cut Nut)

Date: 8/12/2005 7:41:50 AM
Author: adamasgem

Date: 8/11/2005 3:51:22 AM
Author: Garry H (Cut Nut)

Date: 8/10/2005 11:50:46 AM
Author: adamasgem
RE: Gary Holloway: . Have you seen Sergey''s spoon test? do this - carry a spoon with you from room to room (you will have to be awake during the day Marty and i am not sure if that is feasible - so you could ask someone else to do this test ). put the spon upside down at desk top / table top and see the difference between light intensity from windows and ceiling lights - amazingly fluoro lights are not as intense as light from windows - only very bright halogens are more intense - but have much less light - but they contribute to fire because they are smallish point sources.

In one case you diffuse and in the other you concentrate light
the point is that the light from the window is often more diffused but also more intense

I don''t think that consumers give a rats rearend how their diamonds look to strangers in a supermarket, but that is only my opinion..

I am not surprised that you think that, but then you are not exactly the diamontaaires target demographic - diamonds do not sparkle in the dark - especially when they are locked in the coffin

But you can see their FIRE in dimmer lighting, not getting BLASTED out by the glare from typical jewelery store lighting. I''m not concerned about the seller''s perspective, but the users..

I have not made my mind up yet that GIA''s gray tray is good or bad. But i can see that there is no need to now think (as Paul from antwerp has feared) that there is some conspiracy theory at work - because if you tested diamonds on a light enough gray tray then clean leaky stones in bright lighting will look great. And that means the old AGS Steep Deeps that we all contributed to down grading of, could have been better performing stones than we all came to believe.

Is the object of the exercise to objectively evaluate the quantity and quality a diamond''s light return when light enters the crown or when attenuated light (both in intensity and spectrum) enters from below the girdle plane. Exactly Gary I asked a question which you didn''t answer

So again folks - thi is I believe time for us to make some serious re-analysis of all our assumptions.

Is it valid that some light, or enough light enters the pavilion on pieces of worn jewellry in various settings to make GIA''s results valid?

It appears to me that the common viewing environment and the theoretical studies presented are inconsistent there is no doubt in my mind they threw the theoretical computer based ray trace studies in the trash can - especially after some of Ilene Reinitz''s comments in question time 2 or 3 years back at the JCK ''watch this place'' song and dance routine. Did you get on her dance card?

The main question here is - how many diamonds are set so light can get in the back?

I think 99% of earrings and pendants should be modelled on black trays. And my own experiment with Drena''s earrings with one shallow vs one ''ideal'' cut stone in each ear clearly showed that shallower stones make much better earrings when worn and when they have a bit of normal dirt on them. (A number of people observed this test in Vegas this year and all agreed. I conducted the test over about 6 months, and as a reward Drena went from 1ct to 1 1/4ct each ear

). But then again, aren''t you a bit biased towrd shallower stones

like you are biased toward symmetry - you use toys and I use simple experiance

I guess the operative word is "simple" in your case

Now as for rings - say 66%??? are set in 4 or 6 prong settings and can get some light in the pavilion. Reasonable?
Is a say 50% gray tray a reasonable test? It is more reasonable than 100% intensity from the side
Does dirt make this better or worse? Grease, as in body oils, not ''dirt'' per se How should we define ''oils'' Sol? RI? Colour spectrum / absorption etc? Gary, it is the difference between the refractive indices of diamond (2.417 @ 589nm) and air(~1.0) and diamond /oil(~1.5) which opens up the critical angle and lets light escape out the back of the stone. I''ve had the 2D model for this in my Adamas Advantage software since the early 90''s and the 3D modeling in the SAS2000 for the last few years. Look at the Fresnel reflectivity equations and maybe you will understand..
More applicable or less?

 

[adamasgem]

Date: 8/12/2005 9:08:06 AM
Author: strmrdr

Date: 8/12/2005 7:47:14 AM
Author: adamasgem

Date: 8/10/2005 1:18:51 PM

Author: strmrdr

This is fairly typical of ''white'' leds and what Marty is talkin about with them.

Thanks for posting it. The LED color temperature distribution is VERY different than the D65 spectrum used in the GIA fire article

Welcome.
Do you have a similar chart for a good D65 source?
I cant find one online.

The LED spectrum is measured, the solar D65 is based on formulations in Color Science.. Each manufacturers LEDS may differ in relative intensity just as fluorescents having the SAME correlated color temperature (CCT) differ because of phosphors as well as position under the tube..

 

[adamasgem]

Date: 8/12/2005 12:45:27 PM
Author: oldminer
Wow, what a technical article for Pricescope. A lot of good thought is being shared. THANK YOU.

I think the matter is simpler than technical. It is a marketing strategy, possibly based on some flawed ''research'' or even possibly on a degree of satisfactory research, that the decision was taken by GIA to offer a very wide range of ''Excellent'' rather than a more carefully crafted one that discriminates with a finer set of parameters or measures. It is all about selling paper

Folks who have long resisted grading the cut will probably prefer GIA''s version of cut grading to more stringent systems. This will mean that other systems such as AGS, GCAL, Gemex, Ogi, Sarin, Drucker or ImaGem, will be more useful to Internet vendors and high end B&M retailers, than the GIA system. The 95% to 98% majority of consumers don''t care so much about absolute performance anyway, but buy more on impulse and budget constraints. The GIA system may suit this large majority of people better than any narrower, more discerning system. This is good for a lab''s bottom line, but it may not be the best technical method for discriminating performance levels and beauty. It might also be construed as entirely misleading to the consumer.. did I say that??? I guess I did

People are going to want to know about the success of light performance in fancy shapes, too. It appears the GIA is not going forward on that front, but just sticking to rounds. One could say our leader is letting us down a little. One might also say we are being freed to follow our own path in creating standards. Neither is a perfect situation, but I prefer freedom instead of mindlessly following a sadly now questionable ''market leader''. Especially when the industry funds the "leader"

Maybe someday all of us who intend to MEASURE light performance will get together in a secret location and work out our relatively small differences. There should or could be a universal ''Standard''. I''d like to tell consumers we use a ''standard methodology''. I would give credence to the reports we do, and would give some power to labs that are trying to make a real difference. Meanwhile, the debate and sharing is all useful to have on the forum to read and compare.
One of the problems is that some won''t define how they "measure" or the environment used. Some do, then it becomes a discussion on what environment to use, the sellers or the buyers..

As I said before, I think that politics wagged the tail of the dog..

 

[oldminer]

Marty will no doubt disagree, but HOW one measures light is of less importance than a couple other things. WHY one measures light is to judge performance and beauty. Regardless of the lighting environment, if diamonds are placed in proper light performance order from top to bottom grades by a trade secret lighting device, then we have an answer to our needs. I understand that the curious, Marty and others, would want to know more, but you can''t know everything sometimes. Secrets are a legitimate tool of intellectual property rights. Of course, there needs to be some regular room lighting in which to make human, visual judgments. We can''t do human subjective grading in a darkened room. One must remember that the work of determining light performance and its beauty equivalents has been done by several groups. No one is truly saying they are at odds with one another over why and when a diamond looks great or when it does not look very good. The human eye is a good tool for roughly judging beauty, but it does not give a numeric readout. For this, we have created a machine to give us the degree of artificial intelligence that we insist we require to do accurate and consistent grading.

1. Of most importantance is that human eyes can tell if the measurments are legitimate. Can people detect differences between the grades that make sense?
2. Are these measures consistent and repeatable? Will a diamond measured today grade the same, within machine error, when it is re-measured in a week a month or a year?
3. Will the trade actually opt to accept accuracy versus bull s*** and over-liberalism? Without consensus, we are just making ripples in a pond.
4. Diamonds which are overly deep look smaller. It is my belief that while it may not be a Light Performance issue, it bears on Cut Quality issues and ought not to be dismissed as meaningless. A diamond should look good for its weight. A consumer wants a decent spread diameter, not a big depth. Grading that does not address cutting issues is only half a grade.

 

[strmrdr]

Date: 8/12/2005 3:10:52 PM
Author: oldminer
Marty will no doubt disagree, but HOW one measures light is of less importance than a couple other things. WHY one measures light is to judge performance and beauty. Regardless of the lighting environment, if diamonds are placed in proper light performance order from top to bottom grades by a trade secret lighting device, then we have an answer to our needs.

I very strongly disagree too because a diamond performs well in one type of lighting does not mean it will perform well in another.
How a diamond looks in a box is worthless because no one carries diamonds around in a box saying here put your eyeball 2.2 cm from this and see the awesome diamond.
Now the counter claim will be that the lighting duplicates a real world situation. OK which one? There are billions of possibilities.
How do I confirm the rankings in the real world if I dont know how they judged them in the first place.
Gee just trust us oh and thats $19.95 + $100 shipping and handling and it comes with a 30 day money back warranty that started when it was made 6 months ago. :}

 

[strmrdr]

Date: 8/12/2005 2:17:12 PM
Author: adamasgem

Date: 8/12/2005 9:08:06 AM

Author: strmrdr

Date: 8/12/2005 7:47:14 AM

Author: adamasgem

Date: 8/10/2005 1:18:51 PM


Author: strmrdr


This is fairly typical of ''white'' leds and what Marty is talkin about with them.

Thanks for posting it. The LED color temperature distribution is VERY different than the D65 spectrum used in the GIA fire article

Welcome.

Do you have a similar chart for a good D65 source?

I cant find one online.

The LED spectrum is measured, the solar D65 is based on formulations in Color Science.. Each manufacturers LEDS may differ in relative intensity just as fluorescents having the SAME correlated color temperature (CCT) differ because of phosphors as well as position under the tube..

Thanks!

 

[oldminer]

Strmrdr and all:

"I very strongly disagree too because a diamond performs well in one type of lighting does not mean it will perform well in another.
How a diamond looks in a box is worthless because no one carries diamonds around in a box saying here put your eyeball 2.2 cm from this and see the awesome diamond.
Now the counter claim will be that the lighting duplicates a real world situation. OK which one? There are billions of possibilities.
How do I confirm the rankings in the real world if I dont know how they judged them in the first place?"


I hear you and hopefully my explanation will finally make it clearly apparent that you and others are setting up an impossible position to be in or to support. The arguments about lighting models can never be settled. You make it very clear you understand this is a question for which there never will be a proper answer. I agree.

The diamonds that have already been put in a black box number in the thousands. Every one of them was scrutinized for visual performance by lab observers and also machine measured. A statistical database was kept which identifies the components of Brilliancy, Sparkle, and Intensity of each diamond so that we can now measure other diamonds and know which cluster level/range of performance they belong to. This IS an accurate way to process the data and to grade these stones. How the light in the box is arranged is certainly something to you might wonder about, but when one looks at the end results, the correlation to the "looks" of the diamond is what measuring performance is all about. Consumers don't care what's in the box. They want to know the diamond looks like the results indicate it should look. This should be sufficient for gemologists and informed consumers, too.

The light in the box is not complicated but no one has ever said it duplicates ANY real world lighting situation. What good would that be anyway? If we choose any one model, someone else would choose another. Scientists instead select what they'd call a "Normal Lighting Environment" meaning one of their own choosing which gives results that work in the world in which they operate, namely visible light and beauty grading of diamonds by human observers.

The light in the box is not like any environment in a store or a lab, but IT WORKS to give the machine the opportunity to grade diamonds in a way that human observation in regular lighting seems to work in.. Yes, different room lighting gives different results, but beautiful diamonds pretty much look beautiful in all realistic lighting environments. The black box and its readings were extensively tested by some very fine and knowledgeable gemology folks. Of course, others will, in time, independently review the accuracy and discrimination of the readings. Who could expect immediate acceptance? This is a rather large pill to swallow as it will shake up the market structure of diamonds that up til now was based on parameters rather than actual performance.

So, I am saying that the readings WERE confirmed in the REAL WORLD by experienced human eyes. We all recognize that there are "billions" of potential lighting models. Why waste time arguing this point? We all know it cannot be won by anyone and is a fruitless, pointless debate. A more elegant answer was called for and I believe we have it. Right now, no one is well enough informed to disagree with total assurance of being correct. There are lots of half truths circulating probably, but few people have reasonable familiarity with this new technology.

I believe we have selected a successful "Normal" lighting model that gives reliable, repeatable results consistent with extensive human observation. It is a combination of imaging and statistics, something very new to the gem world and to gemologists.

 

[RockDoc]

Well there''s the Ivory Tower ( tech world ) and the Practical World. Both are certainly meaningful, but I believe the consumer needs to evaluate which he prefers, or which side he wants to give the most consideration. This varies from consumer to consumer.

Everyone has good points here but they are made from both sides of the "globe".

I agree with Dave about the light return analysis being standardized, however Gemex has been rather transparent with this, and Ima Gem hasn''t been. ISEE 2 was visited by Marty Haske in Vegas, and because he wouldn''t be buying diamonds from them snubbed him BIG TIME.

They''ve also been uncooperative with me. ( the ISEE2 guys ), requiring I buy their diamonds which for me is senseless cause I couldn''t sell diamonds and remain independent.

As for IMA GEM I called several times, Dave, and didn''t get a response from them. I would certainly love to provide both IMAGEM and GEMEX reports, for those interested. As you know I like providing as much info as possible.

As for Gemex and IMAGEM cooperating together with the intent of a standard... that would in my view, be a plus. Maybe Dave you can find out if this is "do-able".


Rockdoc

 

[oldminer]

No, I don''t think these two firms will work together. The methodology used by Gemex is not oriented to giving discrimination, but rather the kind of happy results vendors and consumers would like to hear. That doesn''t mean it is useless, but the lighting inside their black box does not appear to give results which clearly discriminate the best, the near best, very good, etc. I know it appears to do this, but my sources tell me that it is not doing all it is cracked up to be doing. I know you have a relationship with them and truly want to aid the consumer. It isn''t your desire to help that is underachieving, but the product makes for unsupported results.


I would welcome the opportunity to test some diamonds as a comparison for you and other dealers, vendors. No charge! No secrets.
Constructive criticism is not unwelcome. I believe many firms in this arena want to show how their products work. Knowing the truth will be very powerful. I''d be willing to risk it for the sake of bettering the business. Maybe we can all get the ball rolling.

 

[adamasgem]

Date: 8/12/2005 3:10:52 PM
Author: oldminer
Marty will no doubt disagree, but HOW one measures light is of less importance than a couple other things. WHY one measures light is to judge performance and beauty. Regardless of the lighting environment, if diamonds are placed in proper light performance order from top to bottom grades by a trade secret lighting device, then we have an answer to our needs.

What the trade wants is a black box that you wave the diamond over and out comes a price.

What the consumer wants is a realistic relative grading between stones as to cut, measured or calculated AND correlated to an everyday environment they are most likely to encounter when they and their friends admire and NOTICE their stone..

Part of the "zing" in diamonds is for others to compliment you on them

Part of that consumer "confidence" issue is an openness. As an appraiser, how am I to defend or agree with a number or metric that I have no visibility into. As a technology person, I know that VOODOO for jewelers "science" may be too easy to generate..

I respect those who are open (but may or may not agree), like GEMEX and AGS, and am wary of others. But that is just my opinion.


I think Storm and I agree on this one..

 

[adamasgem]

Date: 8/12/2005 4:00:59 PM
Author: strmrdr

Date: 8/12/2005 3:10:52 PM
Author: oldminer
Marty will no doubt disagree, but HOW one measures light is of less importance than a couple other things. WHY one measures light is to judge performance and beauty. Regardless of the lighting environment, if diamonds are placed in proper light performance order from top to bottom grades by a trade secret lighting device, then we have an answer to our needs.

I very strongly disagree too because a diamond performs well in one type of lighting does not mean it will perform well in another.
How a diamond looks in a box is worthless because no one carries diamonds around in a box saying here put your eyeball 2.2 cm from this and see the awesome diamond.
Now the counter claim will be that the lighting duplicates a real world situation. OK which one? There are billions of possibilities.
How do I confirm the rankings in the real world if I dont know how they judged them in the first place.
Gee just trust us oh and thats $19.95 + $100 shipping and handling and it comes with a 30 day money back warranty that started when it was made 6 months ago. :}

Well said Storm..

 

[Garry H (Cut Nut)]

Gentlemen I would like to bring us back to the topic i raised at the beinning of the thread.

Is a diamond with 36C 41.4P that we know has considerable table leakage (or Marty would say will only reflect light from that area thast has entered the pavilion) an acceptable diamond to be given a top grade?
Is it a fair example of a border line stone that is excellent.
Was the old AGS steep deep at C35.8 P41.2 - that we pooh hooed - was it infact an excellent looking diamond when set in say a 6 prong Tiffany ring?

This stone rates AGS 1 in the old system, and is now AGS 5 in the new system.

I think everyone agrees this stone proportion represents a large difference in results obtained from two respected organizations that have spent considerable effort in estabvlishing their respective standards.

It is arguable that GIA is bending to cutter and trade pressure. It is apparent that aGS have set themselves up to be Holier than Thou - that is their "Idealized" market niche. But I would like to focus on the stone proportions and all things to do with the gIA''s approach, and results please.

I know there are a number of qualified people lurking. If you do not wish to post yourself then ask someone else to on your behalf please.

 

[Garry H (Cut Nut)]

Since AGS use a light return concept borrowed from OctoNus Diamcalc, you can see that the light return for this stone is 91% of that for a Tolkowsky stone for a two eyed ''virtual'' observer.

The mono view suffers more - as explained in my multiple images loaded onto the start of the thread. It shows virtual light return maximum of 89% compared to a Tolkowsky standard.

The 90% leakage, in what Rhino calls the "Ring of Death" is shown here from straight on - but this leakage reduces to less than half when the stone is tilted by say 5 degrees to the view point of what one eye would see. But from the other eyes perspective - the leakage is alomost total. I think that means we would see dark zones - but because GIA placed the stones in light gray colored trays - this means the leakage zone inside the table that each eye sees will probably be ''percieved'' in our mind as a medium amount of light return.

 

[strmrdr]

Garry the best answer to your question is to hunt down a diamond of those specs mount it in a 6 prong tiff setting and buy one you think is better and do the same.
Or better yet mount them both on the same ring side by side even with each other in all ways in 6 prong heads.

Then ask a bunch of people to put the ring on their finger and tell you which looks better and why.

If a vast majority thinks there is no difference then you have your answer they are in the same class.

Baring that then a few opinions is all your going to get.
Put such a diamond beside an ideal cut diamond and Im pretty sure I could pick it out.
I dont think they are in the same class.
But that is the best answer I can give you.

 

[strmrdr]

Hey i just thought of a good demo.
Asschers achieve their patterns by using leakage thru some facets.
I encourage vendors to use a dark background to make the patterns stand out and its easier to see miscut facets.
So my idea is get someone to shoot an asscher against a black, white , and gray background and in one of those fake ring stone holders in the same lighting.
This will give an exagerated idea of the effects of the background when compared to rounds but it will make it plainly visible.
What say you?

 

[strmrdr]

Date: 8/12/2005 9:50:15 PM
Author: adamasgem

Date: 8/12/2005 3:10:52 PM

Author: oldminer

Marty will no doubt disagree, but HOW one measures light is of less importance than a couple other things. WHY one measures light is to judge performance and beauty. Regardless of the lighting environment, if diamonds are placed in proper light performance order from top to bottom grades by a trade secret lighting device, then we have an answer to our needs.

What the trade wants is a black box that you wave the diamond over and out comes a price.


What the consumer wants is a realistic relative grading between stones as to cut, measured or calculated AND correlated to an everyday environment they are most likely to encounter when they and their friends admire and NOTICE their stone..


Part of the ''zing'' in diamonds is for others to compliment you on them


Part of that consumer ''confidence'' issue is an openness. As an appraiser, how am I to defend or agree with a number or metric that I have no visibility into. As a technology person, I know that VOODOO for jewelers ''science'' may be too easy to generate..


I respect those who are open (but may or may not agree), like GEMEX and AGS, and am wary of others. But that is just my opinion.



I think Storm and I agree on this one..

yep we do.

We agree on a lot of things when we arent fighting about the few things we disagree on. :}

It always comes back to lighting lighting lighting when talking diamonds.
From past conversations we agree 100% on that.

Is there a light condition where a "leaky" stone would have an advantage?
Backlight is likely one are there others?

 

[Garry H (Cut Nut)]

Date: 8/12/2005 10:33:05 PM
Author: strmrdr
Hey i just thought of a good demo.
Asschers achieve their patterns by using leakage thru some facets.
I encourage vendors to use a dark background to make the patterns stand out and its easier to see miscut facets.
So my idea is get someone to shoot an asscher against a black, white , and gray background and in one of those fake ring stone holders in the same lighting.
This will give an exagerated idea of the effects of the background when compared to rounds but it will make it plainly visible.
What say you?

An excellent idea Storm.
And if you can get 3D Sarin or Helium files for the stones you can also model them in DiamCalc and use different backgrounds - you do know that the different backgrounds introduce different amounts of back lighting into the virtual stone?

(this type of photography - letting light in the pavilion - has always seemed very deceptive to me - some of you may notice that I get rather short with vendors that do it. It led to me being banned at DT, and a spat with a DT member who posts here recently)

 

[strmrdr]

Date: 8/13/2005 12:53:43 AM
Author: Garry H (Cut Nut)

Date: 8/12/2005 10:33:05 PM

Author: strmrdr

Hey i just thought of a good demo.

Asschers achieve their patterns by using leakage thru some facets.

I encourage vendors to use a dark background to make the patterns stand out and its easier to see miscut facets.

So my idea is get someone to shoot an asscher against a black, white , and gray background and in one of those fake ring stone holders in the same lighting.

This will give an exagerated idea of the effects of the background when compared to rounds but it will make it plainly visible.

What say you?

An excellent idea Storm.

And if you can get 3D Sarin or Helium files for the stones you can also model them in DiamCalc and use different backgrounds - you do know that the different backgrounds introduce different amounts of back lighting into the virtual stone?


(this type of photography - letting light in the pavilion - has always seemed very deceptive to me - some of you may notice that I get rather short with vendors that do it. It led to me being banned at DT, and a spat with a DT member who posts here recently)

Maybe when Jon gets his helium up and running he can get some good files to import into DiamCalc, he has some sarin 3d files up but they dont look right when used in DiamCalc and sometimes have misplaced facets.
The sarin just cant track asschers 100%
If you want to try the sarin files the asschers are here:

http://www.goodoldgold.com/asscher.htm

 

[strmrdr]

hmm this one scanned better than most so might be usefull.
http://www.goodoldgold.com/0_72ct_d_vs2_asscher.htm

 

[adamasgem]

Date: 8/12/2005 10:40:21 PM
Author: strmrdr

Date: 8/12/2005 9:50:15 PM
Author: adamasgem

Date: 8/12/2005 3:10:52 PM

Author: oldminer

Marty will no doubt disagree, but HOW one measures light is of less importance than a couple other things. WHY one measures light is to judge performance and beauty. Regardless of the lighting environment, if diamonds are placed in proper light performance order from top to bottom grades by a trade secret lighting device, then we have an answer to our needs.

What the trade wants is a black box that you wave the diamond over and out comes a price.


What the consumer wants is a realistic relative grading between stones as to cut, measured or calculated AND correlated to an everyday environment they are most likely to encounter when they and their friends admire and NOTICE their stone..


Part of the ''zing'' in diamonds is for others to compliment you on them


Part of that consumer ''confidence'' issue is an openness. As an appraiser, how am I to defend or agree with a number or metric that I have no visibility into. As a technology person, I know that VOODOO for jewelers ''science'' may be too easy to generate..


I respect those who are open (but may or may not agree), like GEMEX and AGS, and am wary of others. But that is just my opinion.



I think Storm and I agree on this one..

yep we do.

We agree on a lot of things when we arent fighting about the few things we disagree on. :}

It always comes back to lighting lighting lighting when talking diamonds.
From past conversations we agree 100% on that.

Is there a light condition where a ''leaky'' stone would have an advantage?
Backlight is likely one are there others?

Storm..
Well said.. lighting lighting lighting..
What we "know" about GIA published work is that the lighting models are probably screwed up..
As to GIA, we don''t know the "weighting" applied to each factor used for their classification, so we can''t say much, are they giving more credence to "brilliance" than "fire" or contrast, etc

Gary''s example above of a ray(s) perpendicular to the table (plane paralle ray front) will give one result or relative "metric" for light return and fire, where their "hemisphere" would give another set of relative result(s).. Neither, in my opinion, represents what I would consider to be justifiable lighting models..

I also believe that limited viewpoint computed metrics, such as generated by reverse raytracing, over a small set of viewing angles, can give (note I say CAN give, not WILL give) misleading relative metrics stone to stone. I think I adequately pointed that out in another thread showing, for three stones, the azimuth and tilt "problems" possible.

The solution is there, only we don''t have the computational resources to do it "correctly" yet. What is going on now in cut grading is on one hand good, and on another, pandering to the trade.

Consumers should understand that diamonds absorb light as the rays pass through the stone, so non light absorbing ray trace models are technically "incorrect" for the real world, and don''t necessarily "reflect" what would actullly happen in their diamond PERIOD. The absorption effects are NON LINEAR, so they cannot be scaled from one size diamond to another, and they are HIGHLY dependent on the light rays chosen to represent the "nominal" environment. "brilliance" and "fire" metrics will scale differently.

These non absorbing models count rays that DON''T exist, because they have been absorbed in the diamond, that what gives diamond its "color", SELECTIVE absorption of light.

As to black boxes (which can''t be modeled, for lack of information), which generate "relative" goodness figures of merit, one will give one set of relative results, where another may give an entirely different set of data. ''TRUST ME, IT IS A "G"'', is trade slang for: if you believe this, then I''ve got a bridge in Brooklyn for sale.

As to "background", either difussely reflecting light exiting the stone and then re-entering through the pavilion, or directly entering from a diffuse or point source, my feeling is that one should be considered and the other not, mainly because of the vast variabilty in settings, of what is "right", and most probably, the backgrond reflected light coming from light that has gone through the stone, should be eliminated in any metric. BUT, light (computationally) should be able to able to hit any crown facet from any angle, as that is most representative of the real world. HOWEVER, INTENSITY, should be a function of source position, AS IN THE REAL WORLD.

In their original work, GIA, in my opinion, CORRECTLY assigned a weighting function to reflect probable viewpoints, but used an INCORRECT, uniform illumination model. Retreating to one viewpoint, was probably a computationally driven decision, with politics saying, "shoot the engineer, get the product out the door".

What has happened with accidents in the space shuttle program, is a clear example of what happens when "management" overrides good judgement.

 

[adamasgem]

Date: 8/13/2005 12:53:43 AM
Author: Garry H (Cut Nut)

(this type of photography - letting light in the pavilion - has always seemed very deceptive to me - some of you may notice that I get rather short with vendors that do it. It led to me being banned at DT, and a spat with a DT member who posts here recently)

Got to agree with you there Gary. Backlighting may be one thing when used in an analysis tool, and an entirely different thing when photographing for sales..

 

[adamasgem]

Date: 8/12/2005 6:31:52 PM
Author: oldminer
No, I don''t think these two firms will work together. The methodology used by Gemex is not oriented to giving discrimination, but rather the kind of happy results vendors and consumers would like to hear. That doesn''t mean it is useless, but the lighting inside their black box does not appear to give results which clearly discriminate the best, the near best, very good, etc. I know it appears to do this, but my sources tell me that it is not doing all it is cracked up to be doing. I know you have a relationship with them and truly want to aid the consumer. It isn''t your desire to help that is underachieving, but the product makes for unsupported results.


I would welcome the opportunity to test some diamonds as a comparison for you and other dealers, vendors. No charge! No secrets.
Constructive criticism is not unwelcome. I believe many firms in this arena want to show how their products work. Knowing the truth will be very powerful. I''d be willing to risk it for the sake of bettering the business. Maybe we can all get the ball rolling.

DAVE: Although I may or may not agree with GEMEX analyses results , as I haven''t done the modeling YET

UNLIKE ISEE2 and IMAGEM

1) THEY are FULLY open disclosure wise
2) THEY do discriminate light performance between stones

 

[Rhino]

Date: 8/9/2005 8:07:20 AM
Author: Garry H (Cut Nut)
Exactly what I am saying Storm.
The brain takes the dominant sparkles or dark zones of strong contrast in the diamond from each eye (not only the info from the dominant eye) and merges the information in our perception.

So therefore if a diamond has a dead dark zone, I believe it will be visible to each eye, unless it is masked by a bright spot.
The stars that you H&A''s freaks love so much are dark zones, but fortunately the eye that sees the dark zone sometimes is over ridden by the sparkle coming from the view point of the other eye.

Very fricken cool Garry. This demonstrates why contrast is so key to diamond performance.

 

[Rhino]

As I''m reading through the first page of this thread and after performing Garry''s lil experiment I note one contradiction. Belle posted GIA''s response to the "brightness" metric and the last sentence of that post says...

These tests confirmed what a vision specialist told us—that when looking at most small objects, a dominant eye takes control.''

Garry... didn''t the point of your test demonstrate that the non dominant eye takes control? This is how it seems to me and contradicts the above statement.

 

[aljdewey]

Date: 8/12/2005 7:41:50 AM
Author: adamasgem


I don''t think that consumers give a rats rearend how their diamonds look to strangers in a supermarket, but that is only my opinion..

Boy, Marty - you don''t know women very well, do ya?

Women are absolutely flattered when they catch someone in the market staring at their ring or ogling their jewelry, and then when they actually compliment you on it? completely flattery.

Don''t kid yourself.

 

[aljdewey]

Date: 8/12/2005 9:50:15 PM
Author: adamasgem


What the consumer wants is a realistic relative grading between stones as to cut, measured or calculated AND correlated to an everyday environment they are most likely to encounter when they and their friends admire and NOTICE their stone..

Part of the ''zing'' in diamonds is for others to compliment you on them

So I guess that would include the folks in the supermarket, then? Apparently, you''ve rethought the question....and come up with the right answer.