Low LGF%? Need advice on this stone

[michaelgem]

Ahhh, now THERE''s an answer I can sink my teeth into. Thanks.
Wink, in the cool of the morning. AC is still broke, so all bets are off for the afternoon.
Wink Jones GG Winfield''s

Thanks, Wink

On a personal note, I always fee bad when something I have written evokes controversy among friends and colleagues. It is often because it is so easy to read into the written word things not intended by the author. It is what makes written communication such a challange.

One of the reasons I direct folks to my articles is that they have undergone extensive pier review resullting in dozens of rewrites and modifications, and after many iterations contain the necessary detail to minimize misunderstandings.

Best wishes,

Michael

 

[WinkHPD]

Date: 7/19/2007 11:03:22 AM
Author: Pyramid
I think the thing that is confusing in some ways although I can see what Michaelgem means about it being an area at the top where all on it are ideal but some are nearer the centre with nuances only experts can see as being different. The thing is my stone is this centre of the sweet spot and as others here know a diamond with its proportions 34/41 56 does not get the 4 Excellents on the HCA. Now Michaelgem says experts see these nuances, including Garry, so maybe they cannot be put into words but if they were better why is the centre of the sweetspot only going to get EX, VG, VG, VG. I know that Garry''s HCA may be a different thing mathematically or scientifically that I don''t understand but if these nuances are better why is the Excellents not there. It is in a way saying they are all ideal, but there are different excellents. The HCA sees them in a different place from the nuances the experts are seeing. If it is the centre of the sweetspot why is the fire etc. not excellent but very good, but then that also goes with what Michaelgem said that the centre is not better the whole sweetspot is ideal for all in it.

One reason may well be that many of us do not agree that 34/41 is in the center of the sweet spot. I do not, Paul does not, John Quixote does not, Brian does not, Bill Bray does not and AGS does not.

Garry does not like Steep deep at all and prefers a shallower pavilion for his sweet spot and he wrote the program for HCA. I think it must have to do with the low angle of light they get down under...

Wink

 

[pyramid]

Wink but according to Michaelgem AGS does.

 

[JohnQuixote]

Date: 7/19/2007 12:30:57 PM
Author: Wink

One reason may well be that many of us do not agree that 34/41 is in the center of the sweet spot. I do not, Paul does not, John Quixote does not, Brian does not, Bill Bray does not and AGS does not.

Garry does not like Steep deep at all and prefers a shallower pavilion for his sweet spot and he wrote the program for HCA. I think it must have to do with the low angle of light they get down under...

Wink

I think it's because many Aussies are skinny and don't obstruct.

 

[pyramid]

Date: 7/19/2007 10:45:35 AM
Author: michaelgem

I observe that both GIA and AGS have almost identical centers to their respective sweet spots for table %, pavilion and crown angle (56%, 41 and 34 degrees.) I am not saying that the center is any better than any other point within the sweet spot. Just the opposite. For example, AGS gives the same Ideal 0 grade to all points within their sweet spot, so this area, by AGS definition, looks like a plateau at the top of the performance mountain, not a peak.

Here. Maybe you mean Wink they have not said that but that is what Michaelgem has observed from their data.

 

[WinkHPD]

Date: 7/19/2007 1:24:48 PM
Author: Pyramid
Wink but according to Michaelgem AGS does.

Actually, as John Quixote''s diagram showed, AGS puts it right on the very edge of their 0 catagory, although it is well inside the 1 area, but can easily receive a 2 or 3 depending on all of the factors. It is one of those stones that can receive a 0, a 1, 2 or even 3, depending on many factors. Yours received a 0 and thus should be and sounds like it is, a great looking stone.

Wink

 

[JohnQuixote]

Date: 7/19/2007 1:24:48 PM
Author: Pyramid

Wink but according to Michaelgem AGS does.

This was covered: See this post in the other thread. Michael decided to use AGS0 and AGS1 grades in his chart. That''s cool since it''s his chart, but if you use the 2006 cutting guidelines for AGS0 only (what they''re telling manufacturers to cut to best qualify for their top grade) the center changes back toward Tolk.

AGSL is a three-dimensional system so using that data is not supported by AGS anyway.
See Strm''s comments 5 posts down from the one I linked.

 

[JohnQuixote]

Date: 7/19/2007 12:22:45 PM
Author: michaelgem

On a personal note, I always fee bad when something I have written evokes controversy among friends and colleagues. It is often because it is so easy to read into the written word things not intended by the author. It is what makes written communication such a challange.

Agree 100%. In fact I have avoided replying in some cases because there are people who take it personally.

With respect Michael, I think your position on the 41/34 combination is well documented by now. We all have opinions and the nice thing is that there is much agreement in general terms. At the risk of 'evoking controversy' with you though

I'd gently suggest that identifying any single combination and pairing it with the words “better” or “superior” makes people bristle.

 

[pyramid]

Date: 7/19/2007 1:47:26 PM
Author: JohnQuixote

Date: 7/19/2007 1:24:48 PM
Author: Pyramid

Wink but according to Michaelgem AGS does.

This was covered: See this post in the other thread. Michael decided to use AGS0 and AGS1 grades in his chart. That''s cool since it''s his chart, but if you use the 2006 cutting guidelines for AGS0 only (what they''re telling manufacturers to cut to best qualify for their top grade) the center changes back toward Tolk.

AGSL is a three-dimensional system so using that data is not supported by AGS anyway.
See Strm''s comments 5 posts down from the one I linked.

Yes I remember seeing this but was just pointing out that the PGS software Serg used also agreed with Michael.

 

[michaelgem]

Date: 7/19/2007 2:05:26 PM
Author: JohnQuixote

Date: 7/19/2007 12:22:45 PM
Author: michaelgem

On a personal note, I always fee bad when something I have written evokes controversy among friends and colleagues. It is often because it is so easy to read into the written word things not intended by the author. It is what makes written communication such a challange.

Agree 100%. In fact I have avoided replying in some cases because there are people who take it personally.

With respect Michael, I think your position on the 41/34 combination is well documented by now. We all have opinions and the nice thing is that there is much agreement in general terms. At the risk of ''evoking controversy'' with you though

I''d gently suggest that identifying any single combination and pairing it with the words “better” or “superior” makes people bristle.

You are absolutely right John.

41 and 34 is just a point on a plateau, not necessarily any higher or lower than its surroundings, just happens to be in the center. What I thought remarkable was the discovery that GIA and AGS had almost identical centers.

Strm has responded very well to Pyramid and others. I want to respond to her comment to Wink: " but according to Michaelgem AGS does."

Wink,

This is why I wanted you to read the article before you formed a negative opinion of my findings.

My Accordance article addressed the comparison of the top 20% of the grades in each system i.e. the GIA EX and AGS Ideal 0 and 1 from the old guidelines.

Comparing the centres of the sweet spots

We compare the GIA''s Excellent range of
crown and pavilion main angles in their 5
grade system and the top two grades in the
AGS''s 11 grade system, because both comprise
approximately the top 20% of each laboratory''s
grading system. Because of the interaction
and interrelationship between the diamond''s
parameters, they must be considered in
relation to each other. This is why both GIA
and AGS provide charts for each table size
showing the range of crown and pavilion main
angle combinations that comprise each grade.

This proved fortuitous when we learned that the sweet spot range of Ideal 0 from the PGS software was a little larger but very similar to the old Guideline’s sweet spot range of Ideal 0 and 1.

The exact numbers are less important than the discovery of how close the respective sweet spot centers agree with each other even though the actual sweet spot ranges are quite different. This is part of what the Accordance article is all about. It is what we can agree on rather than the details everyone fights about. Of course I am aware that the devil is often in the details of the actual shape and area of the sweet spot, but the intent was to show areas of common agreement. Then the discussion could move out from that common point.

Other than that, there may or may not be any more significance to the actual sweet spot center point itself. As I said, it is in the middle of the Ideal plateau not at any significant peak.

For discussion''s sake, an analysis of the output of the PGS software for a 57 table and 3% girdle bezel, 55% Star and 80% lower halves yields the following:

The range of possible Ideal 0 pavilion angles is 40.4 to 41.8, center 41.1. GIA center 41.2 (Same as the article reported)

The range of possible Ideal 0 crown angles is 31 to 37.5, center 34.25. GIA center 33.75; both within a quarter degree of 34.

That is why under the new PGS software, my conclusion that the center is at 41, 34 remains valid. That is only a small part of what I attempt to convey in this work.

Ideal regards,

Michael

 

[JohnQuixote]

Date: 7/19/2007 2:37:54 PM
Author: Pyramid

Yes I remember seeing this but was just pointing out that the PGS software Serg used also agreed with Michael.

Not in a real sense Pyramid, because those are 'fantasy' models, projected with perfect symmetry (impossible in real life). The lab doesn't support it. We would need to have real-life examples to even speculate the chances for diamonds outside 0 on the cut guidelines to actually earn 0 (and then it would be speculation only). Michael's projection is skewed because it included candidates all the way up to 42.2 PA. Meanwhile the cut guidelines figure 41.0 as a conservative ceiling for AGS0.

In reality I rarely see 41/34.5+ earn 0 in light performance. I have seen one example of 41/34.9 but never a 41/35 light performance DQD...much less anything remotely approaching the 42.2 used on that chart. Maybe Michael has real DQD samples? These would be useful to see. The point is, a diamond must actually go to the lab to earn the grade. My personal opinion is that the cut guidelines have more teeth for this application, since anything cut to their strictness is pretty much assured to earn 0. Outside that range it's a stone-by-stone call.

In keeping with that, I want to reiterate that this is not about your diamond, which is beautiful and would earn top grades in any metric.

 

[JohnQuixote]

Date: 7/19/2007 2:53:20 PM
Author: michaelgem


You are absolutely right John.

41 and 34 is just a point on a plateau, not necessarily any higher or lower than its surroundings, just happens to be in the center. What I thought remarkable was the discovery that GIA and AGS had almost identical centers...

Thanks Michael. I appreciate that and you know we see eye to eye on many things.

On the idea of "center" we interpret things differently. Fantasy brackets in sports are cool but there''s a reason they play the games. I think I am erring on the side of caution and you''re erring on the liberal side. Having statistics on actual samples would help, yes?

 

[pyramid]

I understand what you are saying John.

 

[michaelgem]

Date: 7/19/2007 3:28:57 PM
Author: JohnQuixote

Date: 7/19/2007 2:53:20 PM
Author: michaelgem





You are absolutely right John.

41 and 34 is just a point on a plateau, not necessarily any higher or lower than its surroundings, just happens to be in the center. What I thought remarkable was the discovery that GIA and AGS had almost identical centers...

Thanks Michael. I appreciate that and you know we see eye to eye on many things.

On the idea of 'center' we interpret things differently. Fantasy brackets in sports are cool but there's a reason they play the games. I think I am erring on the side of caution and you're erring on the liberal side. Having statistics on actual samples would help, yes?

You are right, John.

Having statistics on actual diamonds run through the lab, if a number of them were between 40.75 to 41.25, and 33 to 35 would be most informative. Dealers like Whiteflash are in a great position to explore this range and obtain statistics from the diamonds they run through AGSL.

I am betting, with the right combinations, such as 41/34 and 41/35 that they will all get Ideal 0's.

If they do not, I and many others will question the PGS software and the grading system it represents, since we believe these diamonds to be on the exalted plateau or sweet spot of Ideal with Ideal beauty/light performance.

Ideal regards,

Michael

 

[WinkHPD]

Date: 7/19/2007 5:10:44 PM
Author: michaelgem
Having statistics on actual diamonds run through the lab, if a number of them were between 40.75 to 41.25, and 33 to 35 would be most informative. Dealers like Whiteflash are in a great position to explore this range and obtain statistics from the diamonds they run through AGSL.

I am betting, with the right combinations, such as 41/34 and 41/35 that they will all get Ideal 0''s.

If they do not, I and many others will question the PGS software and the grading system it represents, since we believe these diamonds to be on the exalted plateau or sweet spot of Ideal with Ideal beauty/light performance.

Ideal regards,

Michael

The problem with your suggestion as I see it is that although they run a great number of stones through AGS, I doubt that they are having ANY cut with those parameters, but I will leave that definitive answer for John.

Wink

 

[WinkHPD]

Hmm, had some portraits taken a month ago, I may use one of them as my avatar.

Shame the avatar changes on every post simultaneously. If not I could use the smiley avatar when I am making a nice post, and the not so smiley avatar when I was cranky...,

I believe the smiley avatar has a lower lip angle (LLA)% of about 85% while the not so smiley avatar has about a 95% LLA

Wink

 

[whatmeworry]

Good one Wink. Yes the one on the left is much more sparkly. The one on the right...well, it''s something only a Marine may approve.

 

[Rhino]

Date: 7/17/2007 4:26:02 AM
Author: Paul-Antwerp
So, just before I go to sleep yesterday, I read what is going on in this thread.

During the night, I toss and turn and dream about LGF''s and Garry (very bad dream), and then, I suddenly realize why Garry is probably right and wrong at the same time.

Then, I wake up and see the whole discussion has evolved in such a way, that I need another day to catch up.

I hate it when that happens. And I hate it even more when I have dreams about Garry.

I''m trying to catch up in this thread as LGF''s are one of my favorite topics. This just threw me. Funny Paul.

 

[Rhino]

Date: 7/17/2007 6:10:44 PM
Author: aljdewey

Date: 7/16/2007 7:28:52 PM
Author: Wink


What I fear, is that when there is a way, people who have seen few if any diamonds will suddenly be ''expert'' enouugh to now declare that this diamond or that diamond is unworthy when the truth is that most of them could not tell it from the diamond deemed worthy with their eyes if their life depended on it. We are paralyzing by analysis when we should be celebrating the beauty.

Wink

AMEN, Brother! This is SOOOOO good that I had to repeat it in loud, red letters!

SPOT ON, Wink. As usual.

On a side note, I''m really wondering how many people walk with their head hovering over their stones? I mean, gosh, at some point, doesn''t a gal let her hand hang down by it''s side......headless? Obstructionless?

In my very humble opinion, the most accurate definition for ''Head Obstruction'' is when a buyer lets his OWN mind-clean data-soup---HIS HEAD---obstruct his ability to see past the paper and gaze upon the STONE.

Ech, it''s very easy hanging out here on PS to let that happen. When I first got here, I really felt like many of these differences were GARGUANTUAN and important. They certainly seemed like it, because otherwise, WHY would so many people spend so MUCH time AGONIZING over such little things? Clearly, they had to be HUGE and noticeable distinctions, right?

Then last year, I hopped a plane and went to Texas to see Brian at WF. That had to be the single biggest reality check I''ve had in life since I got out of college and was faced with my OWN bills!

Over a couple of hours, I saw TONS of stones. I saw stones with 40.6 pavilions. I saw stones with painting. I saw stones without painting. I saw branded H&A stones, and I saw non-branded ideally-cut stones. I saw GIA graded stones, and I saw AGS graded stones.

Know what? They were ALL gorgeous. Know what else? When they were all spread out in front of us, I couldn''t pick out which ones were painted and which weren''t. I couldn''t distinguish between the stone with the 34.7 crown and the 34.9 crown. Heck, I could barely tell the G from the I! They all looked similar.......DANCING with light. In a bunch of instances, the only way to match the diamonds back up with their data jackets was to WEIGH them! Mara was with me on that trip, and she said the same thing.

If you can, I''d REALLY recommend you take yourself to someplace that has a bit of inventory of well cut stones, and see them for yourself. I think you''ll find it totally illuminating.

Good post Wink/Alj.

One reason why I think many (at least those analysts) that participate here on the forum here and especially during that time is because we approached cut grading with much the same logic that clarity and color grading are approached. Diamonds are approached in two fashions or perspectives. A critical perspective and a practical perspective. When it comes to clarity and color, as you know there are tremendous value differences that are strictly determined in a critical examination.

With no grading for cut and specifically light performance prior to June 2005, my approach has always been on the conservative side even when there were no practical visible differences. Much like clarity and color. I totally hear you regarding visual differences and the practical examination and agree. I think what we were all waiting for was to really see just how *critical* the labs were going to get in their examination of cut and light performance. We each have our points regarding what we like and dislike about each system but I think one factor we were all let down on was not including optical symmetry in a grade. Many of us feel it is a great representation of excellent craftsmanship.

Peace,

 

[Cehrabehra]

Date: 7/19/2007 6:02:07 PM
Author: whatmeworry
Good one Wink. Yes the one on the left is much more sparkly. The one on the right...well, it''s something only a Marine may approve.

I like the one on the right - very handsome!

 

[WinkHPD]

Date: 7/19/2007 7:33:23 PM
Author: Rhino
I think one factor we were all let down on was not including optical symmetry in a grade. Many of us feel it is a great representation of excellent craftsmanship.

Peace,

And I believe it has an effect on the overall appearance of light performance, as the contrast itself creates the impression of brilliance.

Wink

 

[Rhino]

Date: 7/18/2007 11:00:15 AM
Author: JohnQuixote

Date: 7/18/2007 3:56:25 AM
Author: Garry H (Cut Nut)

Not to mention the actual person looking at the diamond (perhaps the one constant factor?)?

It''s true that someone big causes more obstruction. Hey, as long as we''re at it maybe we can develop a height-weight reference chart for lower halves %? We could even have different cutouts in our showrooms...

''Excuse me sir, I think this diamond suits you better.''
''But I like that other one.''
''No no. You''re in the welterweight division, I''m afraid you''re restricted to these...''

LOL John. I was going to comment along these lines but not with your biting sarcasm.

If we were going to nit pick the affect of LGF length I would say it depens on what type of effect the consumer wanted to see.

To use 2 extremes ... If you were to take a diamond of the 73-75% variety and couple that with pavilion angles on the shallower end of Id/Ex AND the person viewing the diamond had a short focal lengh and/or a wider body you''re going to generally see a distinct darkness on those mains making the diamond appear more contrasty. This is assuming a diffuse lighting environment. Ie. cloudy day.

On the other side of the spectrum take a thinner person with a longer focal length and put a stone in front of him with LGF''s around the 83-85% zone the mains will not be as dark (because they are thinner) and you''ll see alot of brighness coming off of those LGF''s and of course the more splintery appearance. You can see this via the reflector images Garry posted earlier too showing the short and longer LGF''s. Lots of red on the stone with the longer LGF''s.

So yes, focal length, size of the person viewing the stones etc. No one is really better than the other which is why personal preference and seeing the diamonds is important.

All the best,

 

[elmo]

Date: 7/19/2007 3:22:53 PM
Author: JohnQuixote
We would need to have real-life examples to even speculate the chances for diamonds outside 0 on the cut guidelines to actually earn 0 (and then it would be speculation only)...In reality I rarely see 41/34.5+ earn 0 in light performance. I have seen one example of 41/34.9 but never a 41/35 light performance DQD.

I linked a 41.0/35.1 here about five posts down.

 

[Rhino]

Date: 7/18/2007 3:55:04 PM
Author: Wink

Date: 7/18/2007 3:40:39 PM
Author: Maisie

Date: 7/18/2007 1:22:50 PM
Author: strmrdr

Date: 7/18/2007 1:13:24 PM
Author: Wink
An AGS 0 will be a beautiful stone, it may come in several flavors, but it will be beautiful.

Wink

That''s real hard claim to prove without having seen em all.
Your seeing some of the best AGS0''s from Paul.
How many of the worst combo(which ever that is) none symmetrical ags0''s have you seen?

So an AGS0 could also be a yuk? I thought that the AGS0 would always be a great stone to have? The price seems to imply this.

Maise,

I reiterate, I HAVE NEVER SEEN ONE!

I suppose it is theoretically possible, but I have NEVER SEEN ONE!

Dang it Storm, See what you''ve done.

I have seen stones that would be AGS 4''s and 5''s that were still quite attractive, and who knows what the grade might be on some of the Old European cuts that are incredibly beautiful. (Now those I have seen many that were UGLY!, also many that are incredible!)

I HAVE NEVER SEEN AN UGLY AGS O. Not saying that it could not happen, just saying that it would be incredibly unlikely. Please, can we PLEASE stop trying to scare people?

Maise, here is my personal pledge, and I imagine that John, Jonathon, James, Allen, and Fill in the blank with all the other trusted Pricescope dealers, will take it also. I pledge to look at all the stones I ever sell, and NOT to send them out if they are that possible one stone in however many kazillions that is AGS 0 and somehow manages to be UGLY. I wont even send it out if it is just unattractive. I wont even send it out unless it is beautiful.

Wink hot and cranky in Boise

Disclaimer, I have not seen every AGS 0 cut grade stone in the known universe, one could be hiding out there that I would think is UGLY, I just don''t expect that there is, but hey, I did not see them all, so there could be. I could win the lottery tomorrow, but since I have never bought a ticket, it is unlikely at about the same odds that there is an UGLY AGS 0 out there.

LOL. How are you Wink?

You were correct to put my name there. I think ugly is a rather harsh term but I would say that I would not purcahse or back a stone just because it was an AGS Ideal. I''ve seen some I wouldn''t touch with a 10 foot pole (especially if optical symmetry is a criteria for purchasing decisions). Having said that however, I''ve had AGS Ideals in my possession with pavilion angles over 41 degrees and "traditional" optical symmetry that faced up just fine. There are varying appearances in AGS Ideals, one which is caused by the very subject of this thread, lower girdle facet length. Optical symmetry (in reflected lighting environments) and overpainting are 2 other variables that come to mind that affect appearance within the AGS Ideal grade that I can think of off the cuff.

All the best,

 

[Rhino]

Date: 7/18/2007 2:08:38 PM
Author: Wink

Date: 7/18/2007 1:22:50 PM
Author: strmrdr

Date: 7/18/2007 1:13:24 PM
Author: Wink
An AGS 0 will be a beautiful stone, it may come in several flavors, but it will be beautiful.

Wink

That''s real hard claim to prove without having seen em all.
Your seeing some of the best AGS0''s from Paul.
How many of the worst combo(which ever that is) none symmetrical ags0''s have you seen?

Storm,

Buddy, yes I sell the Infinity diamonds from Paul because I find them to be first among equals. (Go ahead John and Jonathon, feel free to chime in and disagree with me, we can have our own little ''war'' here.)

However, I have looked at tens of thousands of diamonds in my lifetime, and I have never seen one AGS Ideal that I thought was ugly. I have seen some that I like more than others, but that again is a taste issue. I don''t think I have ever taken the time to decide what I thought was the worst possible combo and then looked for it, I have way better things to do.

Wink

I am familiar with Paul''s cutting Wink and I would not disagree. He''s one of the finest. Also, I think "ugly" wouldn''t be a good term even if it was less preferred.

 

[Rhino]

Date: 7/18/2007 5:45:25 PM
Author: Cehrabehra

Date: 7/18/2007 5:42:39 PM
Author: JohnQuixote

And some people are going to pour catsup all over ''em anyway! Ever seen a grown chef cry?

Masie, stay with us.

Just keep it reeeal.

John, I think our shared love of analogies is part of our bond LOL

anyone besides me suddenly hoping for meatloaf for dinner? LOL

How funny Sarah. I really did have meatloaf last night!

 

[Rhino]

Hi Wink,

Just reading your exchange with Mike here as I catch up. I think you''re reading a bit too much into his words. Mike is stating that the 75-80% zone is the center of their ranges, not because of personal preference (which it may be), but as matter of fact (which it is). Mike is good people and has a lot to offer to this community as he does a heckuva job studying and understanding many of the concepts that are discussed on this forum.

Peace,

 

[Rhino]

Date: 7/18/2007 9:06:17 PM
Author: aljdewey

Date: 7/18/2007 11:00:15 AM
Author: JohnQuixote

It''s true that someone big causes more obstruction. Hey, as long as we''re at it maybe we can develop a height-weight reference chart for lower halves %? We could even have different cutouts in our showrooms...

''Excuse me sir, I think this diamond suits you better.''
''But I like that other one.''
''No no. You''re in the welterweight division, I''m afraid you''re restricted to these...''

Please - PLEASE - don''t even suggest it in jest.

Because if you do, I can almost guarantee that the next flap on PS is gonna be whether or not you should buy a given stone based on your height.

This had me rolling especially after I responded to it.

 

[michaelgem]

Author: JohnQuixote
We would need to have real-life examples to even speculate the chances for diamonds outside 0 on the cut guidelines to actually earn 0 (and then it would be speculation only)...In reality I rarely see 41/34.5+ earn 0 in light performance. I have seen one example of 41/34.9 but never a 41/35 light performance DQD.

Having statistics on actual diamonds run through the lab, if a number of them were between 40.75 to 41.25, and 33 to 35 would be most informative.

I am betting, with the right combinations, such as 41/34 and 41/35 that they will all get Ideal 0''s.

If they do not, I and many others will question the PGS software and the grading system it represents, since we believe these diamonds to be on the exalted plateau or sweet spot of Ideal with Ideal beauty/light performance. Michael

Date: 7/19/2007 8:28:46 PM
Author: elmo

I linked a 41.0/35.1 here about five posts down.

Thank you elmo,

Here is an AGS000 under the new performance-based AGS cut grading. I''ve seen several AGS Ideal 0''s recently that were 41/35''s but the reports were not current.

Perhaps they are scarce, because cutters of optically symmetric super ideals are needlessly concerned about deviating that much from Tolkowsky''s angles.

Best/Ideal regards,

Michael

 

[He Scores]

I agree with Paul on most of what he said....as a cutter, some of it I didn''t quite catch., but non-the-less here''s my take.

1. LGF % is an incorrect measurment the way the labs measure it. It is possible to in real life 3 dimensional cutting of a girdle half to increase the angle (measure) and in fact DECREASE the percentage as it is measured from a two dimensional picture like the labs do. Most cutters place the half in it''s proper relationship to the main which is the accurate way to measure it.

Let me explain. Look down on the top of your index finger. We''ll assign three points to it...like the Divine Theory. Point C will be your finger tip. Point B is your middle knuckle and Point A is your knuckle closest to your wrist. Got it?

What you have here is the Divine Proportion...where B-C is 60%(approx) of A-C.

Looking down on your finger, now notice the distance of your finger tip to your middle knuckle (the distance between C-B), as you do, bend finger at the middle knuckle so the tip heads towards the floor and notice how the DISTANCE between points C-B DECREASES. It visually becomes a LESSER percentage of A-C to the point where when it''s bent 90 degrees towards the floor, the percentage is 0!!!!

This is the same thing that happens when a bottom or top half is "DUG" except that the actual ribline created by the digging actually LENGTHENS the ribline but according to the way the GIA measures half lenth, the percentage acrually DECREASES.

Far out huh? Like how wrong can they be? Albertson told me they threw in a 5% fudge factor to compensate this. Nice accurate way of this depicting this facet relationship huh?


TWO: The higher the half, the less angle differentiation between the main and the half. Brilliandeering facets are supposed to "frame" a main facet much like a frame on the picture. The higher the facet, the less contrast there is between the half and main accounting for less "bouncing" of light from facet to facet. This can easily be demonstrated by measurements on the Sarin machine when halves are unduley dug to the point where there is so little differentiation between two halves of a set that the sarin only picks up one measurement. This is a reason why shallow crown stones don''t have the "bounce" of a higher crown stone. "Bounce" is what you see on the Awards shows, when the actresses diamonds are popping like they''re radioactive. Funny thing here.....AGS considers light reflection off a facet surface as a negative. Cutters use this definition to add life to a stone, so any slight movement is highly noticeable.

As a side note: If you take a look at the picture of the American Ideal profile in the GIA''s diamond dictionary, turn the picture upside dow and lay a ruler across on the top of the two sets of bottom halves. You should notice that the ruler isn''t parrallel with either the girdle or the table. The halves aren''t placed equally.


To sum up my view, facet definition is important for the overall real life look of a diamond and not a picture of the diamond and that percentage is only a meaningful range when measured correctly.

Bill Bray
Diamond Cutter