AGS0 Proportions
- Thread starter MarkP1
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decodelighted
Super_Ideal_Rock
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Under the tutorial: Girdle thickness, Culet size, Weight or Spread, Durability (no crown angles below 30°) and Tilt (fish-eye)
But I know that's not what you meant by "'ideal' proportions or range of proportions when grading."
There are only cutting guidelines.
Go to HCA, put in the table you want (47-61,) run it, and the box is that range of proportions.
But I know that's not what you meant by "'ideal' proportions or range of proportions when grading."
There are only cutting guidelines.
Go to HCA, put in the table you want (47-61,) run it, and the box is that range of proportions.
AmyFortner
Rough_Rock
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decodelighted
Super_Ideal_Rock
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I don't think AGS *has* ideal specs determined for any of those cuts yet? But I could be wrong. Those are all cuts that are pretty hard to select by the #s ... but maybe some experts will chime in with their personal fave specs so you can weed some out before calling them in to actually LOOK at ... but I wouldn't buy any of those cuts without seeing them in person ... #s won't tell you about "bow tie" in Ovals, or which type of patterns exist in an Asscher, or whether a square radiant has a "cracked glass" appearance or more "princessy" orderly look to it.
Fancy cuts are a tough road to hoe ... but worth it if that's what you love!
ETA: I guess I was defining "Ideal" as AGS 000 (Rounds & Princesses only). It seems AGS does have cut grade charts for Oval & Square Radiant ... but I'd disagree that the Emerald charts work for Asschers (the Royal Asschers would be severely penalized by their small tables end up 2B or 3A)
I was able to get a hold of this for Round Brilliant cuts...
Does this sound about right???
AGS000:
Table: 52.4% - 57.5%
Crown Angles: 33.7 - 35.8
Crown Height: no recommendation
Girdle Thickness: thin to sl. thick
Pavilion Depth: 42.2% - 43.8%
Culet: none to medium
Total Depth: no recommendation
Does this sound about right???
AGS000:
Table: 52.4% - 57.5%
Crown Angles: 33.7 - 35.8
Crown Height: no recommendation
Girdle Thickness: thin to sl. thick
Pavilion Depth: 42.2% - 43.8%
Culet: none to medium
Total Depth: no recommendation
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Regular Guy
Ideal_Rock
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I think you may find this recent thread helpful.
P.S. a non-sequitur to this, I'm reminded by reviewing the attached thread...Rhino...creative soul that he is, is like my wife, and seems to create many projects, some of which seem to go unfinished. For example, I'll name three:
1) Jonathan, please complete the teaser you introduced in that thread named above
2) I'm sure that the article you mention in it as well..."The Futility of Sarin Numbers," will be interesting
3) you bio in Who's Who is about 3 years on hold. Never too late, you know.
P.S. a non-sequitur to this, I'm reminded by reviewing the attached thread...Rhino...creative soul that he is, is like my wife, and seems to create many projects, some of which seem to go unfinished. For example, I'll name three:
1) Jonathan, please complete the teaser you introduced in that thread named above
2) I'm sure that the article you mention in it as well..."The Futility of Sarin Numbers," will be interesting
3) you bio in Who's Who is about 3 years on hold. Never too late, you know.
JohnQuixote
Ideal_Rock
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The AGS 0 ‘proportions’ concept changed dramatically in July 2005 when AGSL switched to performance-based grading:
The numbers for rounds have been tightened up and are now interdependent - meaning that the angle qualifications change as table size changes. This makes old, static charts for ‘Ideal’ ranges somewhat obsolete.
AGS published cutting charts to assist manufacturers in predicting what will qualify for 0 in light performance, but these are predictive tables only - not a guarantee. Garry has incorporated the new changes for round brilliants into the HCA, which is a great help.
What qualifies for AGS 0 proportions now?
Here is a series of charts you may use to see what's predicted to qualify for AGS Ideal as opposed to GIA EX, and what they have in common, based on table %, crown angle and pavilion angle:
A twist...
If requested by the manufacturer, the AGS will still grade round diamonds using the old proportions-based DQD. The old DQD is easily identified by its blue trim and binder. The new DQD has black trim and the light performance measure is included.
Diamonds at the outer limits of the traditional AGS 0 proportions range may not qualify as AGS 0 under the new metric.
The numbers for rounds have been tightened up and are now interdependent - meaning that the angle qualifications change as table size changes. This makes old, static charts for ‘Ideal’ ranges somewhat obsolete.
AGS published cutting charts to assist manufacturers in predicting what will qualify for 0 in light performance, but these are predictive tables only - not a guarantee. Garry has incorporated the new changes for round brilliants into the HCA, which is a great help.
What qualifies for AGS 0 proportions now?
Here is a series of charts you may use to see what's predicted to qualify for AGS Ideal as opposed to GIA EX, and what they have in common, based on table %, crown angle and pavilion angle:
A twist...
If requested by the manufacturer, the AGS will still grade round diamonds using the old proportions-based DQD. The old DQD is easily identified by its blue trim and binder. The new DQD has black trim and the light performance measure is included.
Diamonds at the outer limits of the traditional AGS 0 proportions range may not qualify as AGS 0 under the new metric.
JohnQuixote
Ideal_Rock
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While we're on the subject, here is a little history…
What used to qualify for AGS 0 proportions?
In 1955 the AGS Diamond Standards Committee was established. In the 60's the AGS 0-10 scale for grading diamond cut was developed, and their Diamond Grading Standards manual was introduced. For the next 30 years it underwent many revisions.
In 1996 AGS Laboratories opened and begin grading diamonds, including cut grading for the round brilliant...based on proportions. It was an independent system, meaning that as long as the measurements all fell within the listed range the diamond would receive ‘Ideal’ in proportions. If the diamond also earned the ‘Ideal’ grade in polish and symmetry it was an AGS 0 in cut. Over the next decade, that system was further tightened and clarified. Here are two examples of ranges that were considered ideal.
In July 2005 AGS began grading based on performance, rather than proportions assessment.
In order to qualify for Ideal in light performance, the diamond is viewed in ASET, modeled & ray-traced. Every diamond must earn certain numeric values for brightness, dispersion, leakage and contrast in the ray-tracing metric to be awarded 0 Ideal in light performance.
Proportions are still considered, but the 0 in proportions is now an analysis of girdle, culet, weight ratio, durability and tilt.
The 0 in finish now assesses both polish and symmetry.
What used to qualify for AGS 0 proportions?
In 1955 the AGS Diamond Standards Committee was established. In the 60's the AGS 0-10 scale for grading diamond cut was developed, and their Diamond Grading Standards manual was introduced. For the next 30 years it underwent many revisions.
In 1996 AGS Laboratories opened and begin grading diamonds, including cut grading for the round brilliant...based on proportions. It was an independent system, meaning that as long as the measurements all fell within the listed range the diamond would receive ‘Ideal’ in proportions. If the diamond also earned the ‘Ideal’ grade in polish and symmetry it was an AGS 0 in cut. Over the next decade, that system was further tightened and clarified. Here are two examples of ranges that were considered ideal.
In July 2005 AGS began grading based on performance, rather than proportions assessment.
In order to qualify for Ideal in light performance, the diamond is viewed in ASET, modeled & ray-traced. Every diamond must earn certain numeric values for brightness, dispersion, leakage and contrast in the ray-tracing metric to be awarded 0 Ideal in light performance.
Proportions are still considered, but the 0 in proportions is now an analysis of girdle, culet, weight ratio, durability and tilt.
The 0 in finish now assesses both polish and symmetry.
JohnQuixote
Ideal_Rock
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Hey Ira, thanks for jogging the memory. That teaser was completed but it was down the page in this thread.
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Past, Present, Future: The Meaning of Three-Stone Engagement Rings
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