adamasgem
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Clarity is used for lower Light Performance by GIA and AGS
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strmrdr
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strmrdr
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adamasgem
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CaptAubrey
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adamasgem
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Date: 8/30/2006 2:13:55 PM
Author: strmrdr
same question to Dave and all the experts.
Now both are D and one is an eyeclean si-2 and the other a IF
Now both d/IF and strong fluorescence and none. Depends on whether or not it is a "True D" or a "New D", and on how much UV is pumped in...
Again, my comments in my previous post on visual perception versus measurement still hold for both these cases. Inclusions, depending on the type, can alter the hue (brown out) or gray out the spectra..
In general, the average consumer probably might not be able to "see" the difference. There is NO ONE answer to the questions posed...
And in the visual comparisons, the differentiation, and the ability to do, so depends on the lighting envirionment and color temperature.
If you have no incident energy in the wavelengths being potentially attenuated by self absorption in the diamond, regardless of the cause, you can''t differentiate whether by eye, or some photometric device. {0.0=I0(wavelength)*k =0.0*k } HENCE my request for disclosure on what is being done.
There is NO SIMPLE ANSWER, Sorry Storm.
I might add to Marty''s previous post that the ability to grade based on color hue discrimination testing also has some impact on what is observed and accurately seen by the grader.
Most of the serious professional organizations require color hue discrimination testing every 2-4 years. Color hue discrimination is of course very important for grading colored stones and fancy color diamonds. While this type of testing reveals color blindness deficiencies, in some cases depending on the type of color blindness it can actually improve the ability to discern grades of colorlessness in diamonds over normal color vision.
When consumers visit here 90% really can''t do this to the extent of a professional, and many times they believe they see something they don''t see. I can count on one hand the consumers that really had accurate colornessness acuity in their vision to discern differences in the high color diamonds.
Those in the forum who attempt to grade color based on photographs posted is really not to be given much weight, if any at all.
Another useful suggestion for those choosing appraisers, is to find if their eyes have been tested, when, and what the result was. They should have a "certificate" from the organization that did the test to PROVE this was done and what if any deficiencies in their vision was/is.
Rockdoc
Most of the serious professional organizations require color hue discrimination testing every 2-4 years. Color hue discrimination is of course very important for grading colored stones and fancy color diamonds. While this type of testing reveals color blindness deficiencies, in some cases depending on the type of color blindness it can actually improve the ability to discern grades of colorlessness in diamonds over normal color vision.
When consumers visit here 90% really can''t do this to the extent of a professional, and many times they believe they see something they don''t see. I can count on one hand the consumers that really had accurate colornessness acuity in their vision to discern differences in the high color diamonds.
Those in the forum who attempt to grade color based on photographs posted is really not to be given much weight, if any at all.
Another useful suggestion for those choosing appraisers, is to find if their eyes have been tested, when, and what the result was. They should have a "certificate" from the organization that did the test to PROVE this was done and what if any deficiencies in their vision was/is.
Rockdoc
adamasgem
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Date: 8/30/2006 3:32:17 PM
Author: RockDoc
I might add to Marty''s previous post that the ability to grade based on color hue discrimination testing also has some impact on what is observed and accurately seen by the grader.
Another useful suggestion for those choosing appraisers, is to find if their eyes have been tested, when, and what the result was. They should have a ''certificate'' from the organization that did the test to PROVE this was done and what if any deficiencies in their vision was/is.
Unless you have that knowledge base for interpretation and the MF100 hue, D15, Ishihara Pseudo Isochromatic plates yourself, and the proper color temperature light source to administer the test yourself, anytime you want to.
In the two times I have paid to have the MF100 hue done "professionally" by medical facilities, once the color chips were obscured by fingerprints and the administor left the room so all one had to do is turn the chips upside down, and in the other case theere was no proper light source. When I watched it being done by an "association" in Las Vegas years back, they used the room lighting. I guess two of the three never heard of metamerism effects.
Now there is a new player (HRR Pseudoisochromatic plates) which people are using because it is easier to administer t.. and adds to the original Isihara tests developed pre WWII, I believe, to test train engineers as to whether they knew the difference between red and green lights. I have multiple versions of it, some dating pre WWI, including one for the illiterate!! ("Unlettered Persons" is the term used).
I think the MF100 Hue may be the most accurate, if properly administered under the correct envirionment.
Rockdoc
adamasgem
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For those interested, here is an example of an Ishihara test plate where you had to trace a meandering line from one X to the other X.. Others require you to tell what number or letter is seen agaist the background. The D15 test is a shortened version of the Munsell Farnsworth 100 Hue using 15 chips. You can sometimes find used copies of these books of Ishihara plates on Ebay.
adamasgem
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adamasgem
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Dave,
The problem lies in those that are calling performance grades, cut grades. I''ve said it from this side of the fence for a long time...there is performance grading and cut grading. Just because a stone performs well, doesn''t mean it''s cut well and visa versa.
You can have a tolkowsky cut with a BrayScore of 950/1000 and no performance. Any evaluation system must account for this or certainly it can''t be called a standard for the industry.
There are about 5 or 6 variables that affect performance. Cut is only one of them.
Bill Bray
Diamond Cutter
The problem lies in those that are calling performance grades, cut grades. I''ve said it from this side of the fence for a long time...there is performance grading and cut grading. Just because a stone performs well, doesn''t mean it''s cut well and visa versa.
You can have a tolkowsky cut with a BrayScore of 950/1000 and no performance. Any evaluation system must account for this or certainly it can''t be called a standard for the industry.
There are about 5 or 6 variables that affect performance. Cut is only one of them.
Bill Bray
Diamond Cutter
Regular Guy
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Bill: You and I agree 100% that a "cut Grade" is made of components that ought to be reported. You cannot just throw light performance and cut craftsmanship into one stew and get the right information.
We use Light Behavior, and combine it with DFS. DFS means durability, finish and size. It is parameter driven, like your superb BrayScore, but a far simpler product which reports satisfactory cutting or denotes the weakness of the cut craft used. It looks at girdle thickness and crown angle for Durability. It looks to Polish and Symmetry for Finish. It finally looks to the relationship of depth to width which is what we refer to as Size in this system. Too much depth and not enough spread is a fault.
The DFS falls from my previous work on the AGA Cut Class grades, but when provided along with a performance grade, we were able to open the craftsmanship standards up and away from strict Tolkowsky. This is what AGS and GIA have also done as regard parameters.
However, I believe one ought not to report everything under one word. We should report light performance AND craftsmanship grades as separate entities. Whatever one chooses to call them is fine, but BOTH are of importance and should not be blended into a single term which might mask a problem that a consumer should be informed of.
Paul from Antwerp has pointed out to me that using depth percentage in the AGS new princess cuts is somewhat a faulty measure. We are going to soon report square mm of face up view so people can compare any stones for their actual visible, face-up size. We may make it a ratio to do with weight, or normalize it to a 1 carat size since weight and spread relationships change normally as weight increases. In essence, we want a meaningful number that consumers and dealers may use to understand the spread of the stone and how well it also performs.
Cut Grading is a lot more than Light Behavior grading alone. While some people want it alone, others may prefer the whole story. We can provide it and do on our reports. We look toward other labs adopting such an open strategy. I have always shared my Cut Class charts and hope the DFS will also "catch on".
I had the opportunity to have several meetings with Sergey at the recent GIA Symposium. We got along a lot better than expected. He is young, very smart, thoughtful and a force to be dealt with in the coming years. We don't see everything in the same light, but competition and collaboration is a good theme for going forward. Yuri was also there from Moscow State U. He runs their gemology education. He tells me that the AGA Cut Class grades are taught all over in Russia to gemological students. These same cut grades are built right into their DiamCalc 3D cut grade program. Even if other labs are larger, they can't forever ignore previous knowledge and work.
We use Light Behavior, and combine it with DFS. DFS means durability, finish and size. It is parameter driven, like your superb BrayScore, but a far simpler product which reports satisfactory cutting or denotes the weakness of the cut craft used. It looks at girdle thickness and crown angle for Durability. It looks to Polish and Symmetry for Finish. It finally looks to the relationship of depth to width which is what we refer to as Size in this system. Too much depth and not enough spread is a fault.
The DFS falls from my previous work on the AGA Cut Class grades, but when provided along with a performance grade, we were able to open the craftsmanship standards up and away from strict Tolkowsky. This is what AGS and GIA have also done as regard parameters.
However, I believe one ought not to report everything under one word. We should report light performance AND craftsmanship grades as separate entities. Whatever one chooses to call them is fine, but BOTH are of importance and should not be blended into a single term which might mask a problem that a consumer should be informed of.
Paul from Antwerp has pointed out to me that using depth percentage in the AGS new princess cuts is somewhat a faulty measure. We are going to soon report square mm of face up view so people can compare any stones for their actual visible, face-up size. We may make it a ratio to do with weight, or normalize it to a 1 carat size since weight and spread relationships change normally as weight increases. In essence, we want a meaningful number that consumers and dealers may use to understand the spread of the stone and how well it also performs.
Cut Grading is a lot more than Light Behavior grading alone. While some people want it alone, others may prefer the whole story. We can provide it and do on our reports. We look toward other labs adopting such an open strategy. I have always shared my Cut Class charts and hope the DFS will also "catch on".
I had the opportunity to have several meetings with Sergey at the recent GIA Symposium. We got along a lot better than expected. He is young, very smart, thoughtful and a force to be dealt with in the coming years. We don't see everything in the same light, but competition and collaboration is a good theme for going forward. Yuri was also there from Moscow State U. He runs their gemology education. He tells me that the AGA Cut Class grades are taught all over in Russia to gemological students. These same cut grades are built right into their DiamCalc 3D cut grade program. Even if other labs are larger, they can't forever ignore previous knowledge and work.
Regular guy...
One of the difficulties of making the correlation between a diamond that performs well and a stone that is cut well is that there are other factors in addition to the quality of the cut that mitigate and in some instances totally negate this relationship. Some of these factors include but may not be limited to:
1. Color or opaqueness of color
2. Clarity
3. Material
4. Fineness of polish beyond just seeing “cutting lines”.
5. Granular structure and subsequent layout of the stone.
If my scoring system would take off there are ways to weight some of them in relationship to performance. For instance, a stone drawing slight color (i.e. I-J-K) would benefit in appearance from a varying degree of angles than say an Ideal cut. But we''re far from there.
Also, some of the items on that list, if they are taken to extremes, (Like the machine guys and my system are forced to do to incorporate error rates and their effect on the final outcome), then you can see that performance grading is only for better material. A badly knaated stone, a cloudy stone, an opague stone all perform much less than fine soft material.
All diamond is not the same.
Bill Bray
Diamond Cutter
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