Diamond Proportions - AGS0 (Ideal) and leakage

[KobiD]

I've read people say AGS0 is a reasonably safe choice, as the stone has to pass light performance tests to receive the 0 score/ideal grading.

I've also read that as you approach the edges of the TIC range (ie 35/40.9) that it can swing either way in regards to light leakage under the table.

Is it possible for a stone to have significant leakage under the table, and still score a 0 for light performance?

I've also noticed most of the stones in this range tend to not have the ASET version of the AGS report. Are they hiding something?

I know an ideal-scope is the test to rule in/out, but was hoping to hear some opinions from those with experience.

 

[Texas Leaguer]

I've read people say AGS0 is a reasonably safe choice, as the stone has to pass light performance tests to receive the 0 score/ideal grading.

I've also read that as you approach the edges of the TIC range (ie 35/40.9) that it can swing either way in regards to light leakage under the table.

Is it possible for a stone to have significant leakage under the table, and still score a 0 for light performance?

I've also noticed most of the stones in this range tend to not have the ASET version of the AGS report. Are they hiding something?

I know an ideal-scope is the test to rule in/out, but was hoping to hear some opinions from those with experience.

Kobi,
It depends on what your definition of "significant" is. Your first statement is very true. AGS0 is a very safe choice from a cut quality standpoint. The light performance testing consists of running 40,000 simulated light rays through an accurate 3D model of the diamond (sarine scan measuring each facet) and analyzing light behavior taking into consideration leakage as one of many LP factors. In order for the diamond to get a grade of 0, none of the factors can register a deficiency greater than .5 on their metric.

Having said that, diamonds on the perimeter of AGS0 can have some deficits that can be seen in static images. Whether these translate to real world visual issues is debatable. The AGS standard is the strictest there is.

Regarding AGS reports that do not contain ASET light maps, it does not necessarily mean anyone is concealing anything. The platinum certificate is the only one that features this additional information. However, the vendor may choose not to get a light map certificate if the optical precision is not to the level that patterns will be attractive.

 

[Karl_K]

Is it possible for a stone to have significant leakage under the table, and still score a 0 for light performance?

I've also noticed most of the stones in this range tend to not have the ASET version of the AGS report. Are they hiding something?

Yes, leakage is counted as contrast and there have been some combos with red in ASET mains and leakage between them that got ags0. They are not the norm however but I would not buy one.
The hca caught it as being less than top of the line.

Maybe, maybe not hiding anything. The optical symmetry may not be that great or it may be one of the out there combos that get ags0 with weird looking ASET.
If I was going by the ags0 report only I would want the ASET image on the report even with it sometimes not being 100% accurate it is better than nothing.

 

[KobiD]

Thanks for the responses.

So in relation to the AGS light performance simulations, by working in 3D are they modelling performance at varying angles as well as from directly above/face down? I assume it also takes into account the complete diamond and reports on variances between lgfs, stars, etc.

As with any sliding scale grade, there will be those that fall towards the point end, and those at that are on the edge of not making the grade. Its clearly documented that here that most feel the GIA Ex scope is too large, and potentially even that AGS0 definitely starts to find the limits for quite a few long term users/enthusiasts. Its also a shortcoming of a grade that it depends on the 'rules' as to where a particular stone falls.

For those looking for a safe option, we're pretty much pushed down the middle of the scope, with ASG Ideal (which will also pass HCA easily). Pleanty with lovely AGS0 stones report higher HCA scores, but I'm yet to see any scope images for these. Most report great performance.. but what is great performance without a benchmark to test against?

Without a physical ASET/IS image, most of what is said is speculation.

I guess, where I am going is that from the time I've spent reading here, its very easy to get caught up in the figures and the chase for the ideal TIC. To want to chase the SI1 that is eye clean. A thin - medium girdle as to not hide too much weight, and minimal total depth for the same reason. You then have personal taste preferences in terms of patterning, lgf percentages influencing arrow sizes, table size and its reflection, and optical symmetry (not to be confused with grading sym). Its easy to see how/why there is a premium price on the branded cuts, as all the leg work is done.

But, for the average punter who wants a nice stone at a price point, are they really going to notice the difference between a high end AGS0 or low end. I think probably not. A whole lot of people are stoked with there poorly cut mall stones. I think its simply a case of regardless of what you end up with, you could probably always want a little something more (be it sparkle, size, fire, smaller arrows, etc).

 

[Karl_K]

But, for the average punter who wants a nice stone at a price point, are they really going to notice the difference between a high end AGS0 or low end. I think probably not.

I disagree outside optimized lighting or bright sunlight side by side a significant number of people might see the difference. And even more would living with the diamonds for 2 weeks.
People tend to get a "wow pretty" mindset when first seeing a particular diamond.
I think its partly human nature that bright sparky things attract them and partly people are taught that diamonds are special.
It takes a while with a diamond or some experience to look at them objectively and some people never do.
A zillion times people have posted: I have had my diamond a week/month/year and its doing something I didn't see until now is that normal for a diamond to do that?????
999 times out of a 1000 it was doing it the whole time.
Once they do notice it, they will see it much more because they are looking for it.

 

[Texas Leaguer]

Thanks for the responses.

So in relation to the AGS light performance simulations, by working in 3D are they modelling performance at varying angles as well as from directly above/face down? I assume it also takes into account the complete diamond and reports on variances between lgfs, stars, etc.

As with any sliding scale grade, there will be those that fall towards the point end, and those at that are on the edge of not making the grade. Its clearly documented that here that most feel the GIA Ex scope is too large, and potentially even that AGS0 definitely starts to find the limits for quite a few long term users/enthusiasts. Its also a shortcoming of a grade that it depends on the 'rules' as to where a particular stone falls.

For those looking for a safe option, we're pretty much pushed down the middle of the scope, with ASG Ideal (which will also pass HCA easily). Pleanty with lovely AGS0 stones report higher HCA scores, but I'm yet to see any scope images for these. Most report great performance.. but what is great performance without a benchmark to test against?

Without a physical ASET/IS image, most of what is said is speculation.

I guess, where I am going is that from the time I've spent reading here, its very easy to get caught up in the figures and the chase for the ideal TIC. To want to chase the SI1 that is eye clean. A thin - medium girdle as to not hide too much weight, and minimal total depth for the same reason. You then have personal taste preferences in terms of patterning, lgf percentages influencing arrow sizes, table size and its reflection, and optical symmetry (not to be confused with grading sym). Its easy to see how/why there is a premium price on the branded cuts, as all the leg work is done.

But, for the average punter who wants a nice stone at a price point, are they really going to notice the difference between a high end AGS0 or low end. I think probably not. A whole lot of people are stoked with there poorly cut mall stones. I think its simply a case of regardless of what you end up with, you could probably always want a little something more (be it sparkle, size, fire, smaller arrows, etc).

Kobi,
I must say that you seem to be a quick study - you are able to boil alot of information down and make sense of it. I will agree that "for the average punter" you are safe with an AGS0 and that you are not likely to see obvious differences between high end and low end. But I also agree with Karl in that those differences can become noticeable over time to the critical observer.

Part of what is valuable about a high precision cut is how it outperforms less precise cuts across a full range of light environments. The differences are subtle but real. When you think of a diamond as a tiny three dimensional sculpture that owes it beauty to the interaction of its complex system of tiny mirrors, you can understand how the level 3D alignment of those mirrors can impact beauty in nuanced ways.

Again, this takes you back to the original question of whether some deficit in a AGS0 would be "significant". It just depends on your tolerances and what is "significant" to you. Virtually everyone makes some compromises in choosing a diamond. It's a very individual matter as to where you are comfortable compromising. As long as you have all the information at your disposal about the diamond, you can make an informed choice.

 

[KobiD]

I'm following, and appreciate the stream of experience that's being shared. Great points made by both of you, and I can relate to all of it.

From what I have gathered so far, every stone has varying levels of performance. Its part of what makes them unique. Even two stones sharing very similar proportions will have subtle differences. The AGS0 grade is a fairly narrow scope and while with a keen eye (and various tools available) I'm sure its not hard to pick better performers out of the grade - specifically, this is what the retailers are doing with their branded cuts.

In saying that, it does sound unlikely for an AGS0 to exhibit a high volume of light leakage, but may show some compared to a more ideal proportioned cut of the same stone (ie 35/40.9 vs 34.5/40.75). Side by side, differences are likely notable if compared closely/scrutinized, however exactly how much will also be dependant on the other various factors (some of which boil down to personal preference).

So this is the compromise, and as stated, almost everyone makes compromise. Which leaves us with acceptance being the key here. As long as you can accept your stone for what it is. Be it the finer details you love, or love to hate!

A simple example is the lower girdles. I think I prefer shorter thicker arrows for their broader flashes of fire when they are on, but dislike the darkness they can display during partial obscuration. Speaking of which, I have seen the term "Obscuration issue" thrown around here a little. At which stage does obscuration become complication? Do all diamonds exhibit it to a certain extent?

Even when discussing a diamond performing in a large range of conditions, its very open regarding what 'performance' is, and what is simply character. From what I have seen in my limited exposure, is that there is a significant variance in how they appear in different scenarios. From completely white and brilliant, through to dark and firey, with mixes in between.

 

[KobiD]

But, for the average punter who wants a nice stone at a price point, are they really going to notice the difference between a high end AGS0 or low end. I think probably not.

I disagree outside optimized lighting or bright sunlight side by side a significant number of people might see the difference. And even more would living with the diamonds for 2 weeks.
People tend to get a "wow pretty" mindset when first seeing a particular diamond.
I think its partly human nature that bright sparky things attract them and partly people are taught that diamonds are special.
It takes a while with a diamond or some experience to look at them objectively and some people never do.
A zillion times people have posted: I have had my diamond a week/month/year and its doing something I didn't see until now is that normal for a diamond to do that?????
999 times out of a 1000 it was doing it the whole time.
Once they do notice it, they will see it much more because they are looking for it.

I've bolded my orginal post. Probably should clarify, I was suggesting the difference between a top performing AGS0, and something bordering towards AGS1. I have no doubt an AGS0 blows a good/very good cut away across a range of lighting conditions.

 

[Karl_K]

In saying that, it does sound unlikely for an AGS0 to exhibit a high volume of light leakage, but may show some compared to a more ideal proportioned cut of the same stone (ie 35/40.9 vs 34.5/40.75).

The low end of ags0 vs high end ags0 goes well beyond 35/40.9 vs 34.5/40.75 both of which might get ags0 and be in the high end.

 

[Karl_K]

I've bolded my orginal post. Probably should clarify, I was suggesting the difference between a top performing AGS0, and something bordering towards AGS1. I have no doubt an AGS0 blows a good/very good cut away across a range of lighting conditions.

here is the thing there are many ags1(cut grade only, not counting those knocked down for finish) stones that would likely blow away some of the low end ags0 stones when viewed in person.
Remember that the ags0 grade is based mostly on brightness with a nod to contrast with the rest being smaller modifiers and is based on very close viewing conditions.
A stone grades the brightness level and not too much contrast is going to get the grade unless it hits some of the artificial number limits or finish limits.
That does not mean how it gets its brightness and contrast is desirable.

 

[Karl_K]

re obstruction issues:
obstruction depends on distance.
aset is based on 30 degrees and IS is based on 24 degrees that is 8" and 12" viewing distance.

When viewed close obstruction is a good thing if there isn't too much, it actually provides contrast in the diamond and makes it look brighter however one the distance is past the point where the viewer can see the details and the small details blend it can make the diamond look overall darker.
So the best obstruction levels are one that provides contrast(darkness) up close under high degrees of obstruction and doesn't cover to much of the stone but goes away at longer viewing distances with lower degrees of obstruction.
I generally consider half arms length to be the point beyond which it should be minimal.
In general that means a pavilion angle above 40.6 unless it has a very high crown to compensate once it hits 40.4 pavilion angle there is going to be some issues no matter the crown.
On the other side of the coin at 41.4 pavilion angle color entrapment is going to be an issue no matter what the crown.
I like to stay under 41.2 with a complimentary crown.
There are ags0 stones with 41.2+ pavilions and even some with 41.4+.

 

[KobiD]

More great info! Thanks Karl.