Ellen
Super_Ideal_Rock
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Brilliancescope and ACA diamond
- Thread starter pinktiger
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May I try to bring back some reason into this whole argument? Please take two steps back, and look at it from a different point of view. There are two subjects here, and I would like to address both of them:
1. The Brilliancescope
The technics and scientific basis of this machine have been discussed here for ages, and the final idea is that its results are highly debatable. In rounds, there still seems to be some correlation with human observation, but in fancy shapes, it is said to go haywire. Of course, most of this is based upon earlier versions of the machine, and those who dished it years ago, are not testing its newest updates, of course.
All in all, the safest bet is NOT to base a purchasing decision on this machine or its results.
2. LGF in a round brilliant
From history, we are used to basing our assessments on the average main pavillion angle, while most of the surface-area of the pavilion is made up by the lower-girdle-facets. It would probably make more sense if we would work with the angle of the LGF''s as a basis.
The length of LGF is a result of the relationship (the difference in angle) between the main facets and the LGF''s. So, with the same angle of the LGF, and the same length, we would be having a different main pavilion angle. This clearly shows that, in our current way of talking, we cannot look at the LGF-length on its own merit.
Suppose two stones have the same LGF-angle of 42.0°. Stone A has a main pavilion angle of 40.6°, resulting in LGF-length of around 75%. Stone B has a main pavilion angle of 40.8°, resulting in LGF-length of around 77%.
Summary: If we want to talk about LGF-length, we cannot look at this figure unless it is in relation with the main pavilion-angle. OR we can step away from the main pavilion angle, and first use the angle of the LGF in our assessment. Then, we can use LGF as a secondary assessment.
Hope that this is clear.
Live long,
1. The Brilliancescope
The technics and scientific basis of this machine have been discussed here for ages, and the final idea is that its results are highly debatable. In rounds, there still seems to be some correlation with human observation, but in fancy shapes, it is said to go haywire. Of course, most of this is based upon earlier versions of the machine, and those who dished it years ago, are not testing its newest updates, of course.
All in all, the safest bet is NOT to base a purchasing decision on this machine or its results.
2. LGF in a round brilliant
From history, we are used to basing our assessments on the average main pavillion angle, while most of the surface-area of the pavilion is made up by the lower-girdle-facets. It would probably make more sense if we would work with the angle of the LGF''s as a basis.
The length of LGF is a result of the relationship (the difference in angle) between the main facets and the LGF''s. So, with the same angle of the LGF, and the same length, we would be having a different main pavilion angle. This clearly shows that, in our current way of talking, we cannot look at the LGF-length on its own merit.
Suppose two stones have the same LGF-angle of 42.0°. Stone A has a main pavilion angle of 40.6°, resulting in LGF-length of around 75%. Stone B has a main pavilion angle of 40.8°, resulting in LGF-length of around 77%.
Summary: If we want to talk about LGF-length, we cannot look at this figure unless it is in relation with the main pavilion-angle. OR we can step away from the main pavilion angle, and first use the angle of the LGF in our assessment. Then, we can use LGF as a secondary assessment.
Hope that this is clear.
Live long,
Finding_Neverland
Shiny_Rock
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Loudaway,..............
John Q did a Webinar about this on Saturday.
If,..... and again I say, IF,.......... I followed his explanation of lgf to performance correlation, of the 2 diamonds stats you posted,..........
The first one with shorter lgf's should yield larger, chunkier flashes of light and color. Fewer, but larger.
The second one, with the longer lgf's should yield smaller, but more frequent flashes of light and color.
One diamond will be very dramatic in performance while the other will be more subtle and romantic.
Hopefully I got that right based on what I heard.
If not, hopefully one of the more seasoned Vets or a pro will correct me there.
And I see that Paul Slegers posted just as I did. And there's the crown/pavillion angle relationship to consider as well.
John Q did a Webinar about this on Saturday.
If,..... and again I say, IF,.......... I followed his explanation of lgf to performance correlation, of the 2 diamonds stats you posted,..........
The first one with shorter lgf's should yield larger, chunkier flashes of light and color. Fewer, but larger.
The second one, with the longer lgf's should yield smaller, but more frequent flashes of light and color.
One diamond will be very dramatic in performance while the other will be more subtle and romantic.
Hopefully I got that right based on what I heard.
If not, hopefully one of the more seasoned Vets or a pro will correct me there.
And I see that Paul Slegers posted just as I did. And there's the crown/pavillion angle relationship to consider as well.
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Part of the problem is the guru-syndrome.
We as consumers tend to rely on a guru instead of learning for ourselves.
That's our fault.
Learning is hard.
Diamond cutting is very complicated.
I'm an engineer and I'm supposed to be a smart guy, but I hit a wall trying to wrap my brain around some of this stuff.
I respect anyone who learns the deeper technical stuff.
Next there is the whole Internet Forum dynamic.
There are sellers, cutters and appraisers.
There are consumers.
Their roles are clear.
But then there are "prosumers", people not in the industry who love to learn and dispense knowledge.
This is not necessarily a bad thing.
It is nice they do not have a financial interest in their advice.
It does save the pros from having to answer the same low-level newbie questions 88 times a day.
But I think once you start dishing out more technical advice you have to assume more responsibility and be ready for challenges.
And I'd be sensitive about giving advice that directs customers towards or away from this or that vendor.
I don't want to get personal, but I do agree with Wink's advice.
I have to watch myself too.
I have found myself regurgitating stuff that turned out to be not completely correct.
We as consumers tend to rely on a guru instead of learning for ourselves.
That's our fault.
Learning is hard.
Diamond cutting is very complicated.
I'm an engineer and I'm supposed to be a smart guy, but I hit a wall trying to wrap my brain around some of this stuff.
I respect anyone who learns the deeper technical stuff.
Next there is the whole Internet Forum dynamic.
There are sellers, cutters and appraisers.
There are consumers.
Their roles are clear.
But then there are "prosumers", people not in the industry who love to learn and dispense knowledge.
This is not necessarily a bad thing.
It is nice they do not have a financial interest in their advice.
It does save the pros from having to answer the same low-level newbie questions 88 times a day.
But I think once you start dishing out more technical advice you have to assume more responsibility and be ready for challenges.
And I'd be sensitive about giving advice that directs customers towards or away from this or that vendor.
I don't want to get personal, but I do agree with Wink's advice.
I have to watch myself too.
I have found myself regurgitating stuff that turned out to be not completely correct.
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Paul, thank you for your clear comment and explaination. It helps to know more about this issue, and I do not even begin to claim to have a handle on its complexities.
Just to be perfectly clear, Storm and I are friends and I have a great deal of respect for him. I also strongly dissagreed with what I perceived to be an issue and have perhaps been intemporate for discussing it publicly. I stand by what I said, but I want it to be crystal clear that this was a dissagreement about an issue, not about Storm as a person.
I have great confidence that he and I will continue to agree and dissagree about many things, and I am looking forward to those discussions.
Wink
Just to be perfectly clear, Storm and I are friends and I have a great deal of respect for him. I also strongly dissagreed with what I perceived to be an issue and have perhaps been intemporate for discussing it publicly. I stand by what I said, but I want it to be crystal clear that this was a dissagreement about an issue, not about Storm as a person.
I have great confidence that he and I will continue to agree and dissagree about many things, and I am looking forward to those discussions.
Wink
Ellen
Super_Ideal_Rock
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Paul, I don''t doubt what you''re saying, although I think this is the first time I''ve heard a pro bring it up as an issue to consider when discussing lgf''s. My thought is, but in the end, we''re back to a resulting 75 and 77 lgf. Isn''t that all we really need to know? It just seems like you''re post is making it harder than it has to be. But maybe I''m missing something?
And maybe this would be a good webinar for you to give in the future.
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I am trying to make it easier, not harder, but in that case, we need to take a few steps backwards, and re-assess what we think we know.
There are two major aspects to LGF-length, that is its effect on brilliance and its effect on scintillation. I think that its effect on fire is minimal, and in any case, it goes along with brilliance in this case.
In brilliance, because of the bigger surface-area, the angle of the LGF is basically most important. Sadly however, we are used to working with the angles of the main facets. If we would use the angle of the LGF, and then use LGF-length separately as a secondary discriminator, that would be correct. If we want to use LGF-length, while using main pavilion angle, then they have to be assessed together, at the same time. Therefore, in considering brilliance, LGF-length as such has no meaning, unless we are talking about a very small range in main pavilion angle and a rather broad range of LGF-length.
In scintillation, the size of the virtual facets and the contrast between the facets is important. Therefore, long LGF''s give more pinfire-flash, while short LGF''s give bolder flashes.
And all this is of course, in the understanding that the crown-area remains the same.
Live long,
Guys, I am sorry that my question stirred up the whole thing. I appreciate everyone who gave me suggestions, no matter it is biased or unbiased, positive or negative. No matter what, I know more than before, which is always a good thing 
. Although sometime too much information may not be a good thing, I blieve by knowing more, especially before purchasing it did give customer more freedom/comfort. by knowing more, the asymmetric information between buyer/seller will be minimized, which is one of the reason people like me prefer to purchse it online instead of getting rip off by my local jewler.
Again, I learn a tons in the past weeks, and I really enjoy it!
. Although sometime too much information may not be a good thing, I blieve by knowing more, especially before purchasing it did give customer more freedom/comfort. by knowing more, the asymmetric information between buyer/seller will be minimized, which is one of the reason people like me prefer to purchse it online instead of getting rip off by my local jewler. Again, I learn a tons in the past weeks, and I really enjoy it!
strmrdr
Super_Ideal_Rock
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I decided not to go into the 808 level and just post my thoughts and opinions on the matter.
I think that everyone will agree that that the basic performance of the diamond is set by the crown/pavilion angle and their relationship and with the RB's we typically run into here the minor facets are a modifier they don't set the performance curve.
I like to call it changing the "personality"* of the diamond performance.
The b-scope by its design rewards diamonds with more directional light return because they are the ones that return more light to the camera where non-directional stones the return may miss the camera.
edit cuz I forgot to add it: long lgf% move the diamond towards being more directional and the short lgf% towards less directional.
The 34.0/41 combo is a directional combo and the lgf% isn't a strong enough influence to move it out of the triple vh category(make it less directional enough for it to take a hit in score)
With other combos the lgf% has a greater or lesser effect in the b-scope.
At 34.8/40.8 and around there changing the lgf% is enough to move the bar on the b-scope because the angle combo is balanced between directional and non-directional as far as the b-scope is concerned.
What is interesting and maybe unrelated is that Brian picked that basic c/p angle combo as being well balanced outside the b-scope in the real world too.
That is my opinion in very simplified form on the matter from studying hundreds of b-scope readings over the years and comparing them to the measurements of the stones and knowing the basic design of the b-scope.
* "appearance" "charactor" "style" could also be used here.
strmrdr
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No need to be sorry....Date: 1/29/2007 12:05:28 PM
Author: loudway
Guys, I am sorry that my question stirred up the whole thing. I appreciate everyone who gave me suggestions, no matter it is biased or unbiased, positive or negative. No matter what, I know more than before, which is always a good thing
Again, I learn a tons in the past weeks, and I really enjoy it!
The key is that PS is really a big somewhat disfunctional family with complex relationships.
In one thread it can look like we disagree on everything while at the same time in another thread we are in 100% agreement on something else.
Both the lgf and b-scope subject get pushed back to the back burner then get brought out to be discussed then pushed back again.
Its not your fault and its all kewl :}
strmrdr
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Paul
These are some very well thought out and pertinent issues.
I''d just like to add a little about the angles and lengths, that might not be clear.
Years ago we didn''t know how to get reasonably accurate measurements. We hand "hand tools" and a proportion scope divice, that was good for pavilion depth, but that only gave us very approximate angles.
Then along came Sarin.. and the "world" changed. We were able to get a lot more angle and percentage information - previously only estimated by eye.
Then along came other scanners, and with it difference in how the angles, percentages, or length are measured.
Sarin measures differently than OGI. I think even Helium measures slightly differently than Sarin.
It is my understand that the Sarin measures from the girdle to the meet point where the lgf is. It is my understanding that OGI measures this differently, starting at the girdle then measuring down a straight line, and then measuring across to the lgf meet point.
If I were good at graphics, I could illustrate this. These varying ways of measuring do result in slightly different results.
While it certainly makes logical sense that the accuracy of the measurements could be more exact, current technology isn''t quite there yet, and there is a level of variance or tolerance, that is small and minute, but does exist nonetheless.
Then, each piece of diamond rough is different. Orientation to the grain also plays a part in facet angle selected by the cutter. Not every diamond wants to cooperate with this. Some diamonds just do not want to do what the cutter would prefer so the angles need to be tweaked as the stone is cut to get the polish to the level the cutter wants.
Brian, Bill Bray, and Paul and some others, do cut some amazing diamonds. However, it does take years of experience to understand the differences.
Those who cut diamonds, analyze the qualities, and those who sell all have different understandings and experience. In the last few years, the gap of sharing information has been shared more, and we all know a little more about what the other''s experiences and positions are.
As for the manufacturers of the equipment and the grading labs, continuing development with consistent improvements are happening too. Software and hardware are being improved. I think cutters have learned a lot from the AGS LAB, in being able to produce better finished, and "livelier" diamonds. Appraisers have more and better tools to assess qualities as well. Sellers have a different and far broader means of selecting inventory and understanding qualities far better than just a few years ago.
It is obvious that improvement, change, and accuracy will evolve. Standards will probably become more close and aligned with each other too in the future. We''ll just have to see.
Rockdoc
These are some very well thought out and pertinent issues.
I''d just like to add a little about the angles and lengths, that might not be clear.
Years ago we didn''t know how to get reasonably accurate measurements. We hand "hand tools" and a proportion scope divice, that was good for pavilion depth, but that only gave us very approximate angles.
Then along came Sarin.. and the "world" changed. We were able to get a lot more angle and percentage information - previously only estimated by eye.
Then along came other scanners, and with it difference in how the angles, percentages, or length are measured.
Sarin measures differently than OGI. I think even Helium measures slightly differently than Sarin.
It is my understand that the Sarin measures from the girdle to the meet point where the lgf is. It is my understanding that OGI measures this differently, starting at the girdle then measuring down a straight line, and then measuring across to the lgf meet point.
If I were good at graphics, I could illustrate this. These varying ways of measuring do result in slightly different results.
While it certainly makes logical sense that the accuracy of the measurements could be more exact, current technology isn''t quite there yet, and there is a level of variance or tolerance, that is small and minute, but does exist nonetheless.
Then, each piece of diamond rough is different. Orientation to the grain also plays a part in facet angle selected by the cutter. Not every diamond wants to cooperate with this. Some diamonds just do not want to do what the cutter would prefer so the angles need to be tweaked as the stone is cut to get the polish to the level the cutter wants.
Brian, Bill Bray, and Paul and some others, do cut some amazing diamonds. However, it does take years of experience to understand the differences.
Those who cut diamonds, analyze the qualities, and those who sell all have different understandings and experience. In the last few years, the gap of sharing information has been shared more, and we all know a little more about what the other''s experiences and positions are.
As for the manufacturers of the equipment and the grading labs, continuing development with consistent improvements are happening too. Software and hardware are being improved. I think cutters have learned a lot from the AGS LAB, in being able to produce better finished, and "livelier" diamonds. Appraisers have more and better tools to assess qualities as well. Sellers have a different and far broader means of selecting inventory and understanding qualities far better than just a few years ago.
It is obvious that improvement, change, and accuracy will evolve. Standards will probably become more close and aligned with each other too in the future. We''ll just have to see.
Rockdoc
strmrdr
Super_Ideal_Rock
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Ellen
Super_Ideal_Rock
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Ellen
Super_Ideal_Rock
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Finding_Neverland
Shiny_Rock
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adamasgem
Brilliant_Rock
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I found another way of rephrasing the aspect of brilliance and LGF''s.
With the crown remaining equal, brilliance can be assessed by studying the pavilion. Now, what is important are the angles of the facets, since they direct the light. The length of the LGF is only the result of the relationship between the angles of the main facets and the lower girdle facets. The smaller the difference in angle, the longer the LGF''s.
Because of the higher surface area, it is logical that the angle of the LGF is more important than the angle of the main facets. However, historically, it was impractical to measure the LGF''s, and thus, we have the historical problem that all science is based upon the angles of the main facets.
If we want to study the whole pavilion, we have three options of using two measurements:
A. the angle of the main facets plus the length of the LGF''s
B. the angles of both main facets and LGF''s
C. the angle of the LGF''s plus the length of the LGF''s
Of these three options the first one is the least informational.
Live long,
With the crown remaining equal, brilliance can be assessed by studying the pavilion. Now, what is important are the angles of the facets, since they direct the light. The length of the LGF is only the result of the relationship between the angles of the main facets and the lower girdle facets. The smaller the difference in angle, the longer the LGF''s.
Because of the higher surface area, it is logical that the angle of the LGF is more important than the angle of the main facets. However, historically, it was impractical to measure the LGF''s, and thus, we have the historical problem that all science is based upon the angles of the main facets.
If we want to study the whole pavilion, we have three options of using two measurements:
A. the angle of the main facets plus the length of the LGF''s
B. the angles of both main facets and LGF''s
C. the angle of the LGF''s plus the length of the LGF''s
Of these three options the first one is the least informational.
Live long,
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Hi Paul - sorry I missed you this morning - I had a 7am staff meeting.
This graphic shows what you are saying - one has 75% lgf length - the other is 85%
But both have 42 degree lgf''s. Note the surface area of the 85% is larger than that for 75%.
At 50% the lgf''s = the main facets area, and at 100% there is 0% main facets.
Hope this helps you make your point
This graphic shows what you are saying - one has 75% lgf length - the other is 85%
But both have 42 degree lgf''s. Note the surface area of the 85% is larger than that for 75%.
At 50% the lgf''s = the main facets area, and at 100% there is 0% main facets.
Hope this helps you make your point
strmrdr
Super_Ideal_Rock
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Interesting Paul but I wonder if its that easy...
Notice in the DC images that Garry put up that with equal lgf angles one combo is starting to ring of death.
That indicates to me that there is more too it than lgf angle but also agree that there is more too it than pavilion angle too.
But which is the driver and which is the modifier.
I still think the pavilion mains are the drivers at this point.
Notice in the DC images that Garry put up that with equal lgf angles one combo is starting to ring of death.
That indicates to me that there is more too it than lgf angle but also agree that there is more too it than pavilion angle too.
But which is the driver and which is the modifier.
I still think the pavilion mains are the drivers at this point.
All ACA ("A Cut Above" AKA Whiteflash) diamonds are is AGS-0 or GIA Ex cut diamonds that they've bought, put their label on, and are reselling. Their hearts & arrows tend to be a little more crisp, because of the cutter they get their diamonds from, but that's really about it. Nothing special about them, you can get any AGS-0 cut diamond and there shouldn't be a difference. They're not rejecting any AGS-0 diamonds because they don't meet their standards or anything.
The problem is now and then you'll get an AGS-0 or GIA-Ex cut diamond that doesn't score very well on the brilliancescope for whatever reason. Now they've went and bought this very well cut expensive diamond and the brilliancescope actually kills their sale. Is this the brilliancescope's fault because it's flawed? That's debateable depending on which side of the story benefits you the most. But I'll tell you this much- putting a diamond in a machine, flashing light at it from different angles, and recording the light returned is not a bad idea that's for sure, and it's really the only objective way to measure a diamond's brilliance.
The problem is now and then you'll get an AGS-0 or GIA-Ex cut diamond that doesn't score very well on the brilliancescope for whatever reason. Now they've went and bought this very well cut expensive diamond and the brilliancescope actually kills their sale. Is this the brilliancescope's fault because it's flawed? That's debateable depending on which side of the story benefits you the most. But I'll tell you this much- putting a diamond in a machine, flashing light at it from different angles, and recording the light returned is not a bad idea that's for sure, and it's really the only objective way to measure a diamond's brilliance.
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The same could be said for GIA''s survey - but that did not work either.
Police use radar guns to measure car speeds - but they get spurious results - like the stationary building that was caught speeding etc
If it were that simple Shiatsu, it would be great.
1+1 = 2, but life is not always that simple.
2/3rds of our brain functions are involved in processing visual data - when they know how to program the capture system to process data the same way we do - then they only need solve the problem of the type of light, the viewing distances, the angle of inceidence, the environmental color and amient lighting, the correct amount of back light entering the pavilion...........I could go on
That's true they only show idealscope images on their site, not H & A images. Yet, you're not likely to find an AGS-0 or GIA-Ex cut diamond that doesn't have good hearts. Here's the diamond I bought and took a picture of myself through a cheap $15 H & A viewer:
This wasn't a branded diamond or anything. Just a random GIA graded Ex-Ex-Ex cut diamond.
aljdewey
Ideal_Rock
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Shiatsu, I think you''ve picked up a good deal of faulty information along the way.
They aren''t simply stones bought by Whiteflash from some source. They are cut according to specific parameters at Brian Gavin''s instruction.....that is to say, he tells the cutting house(s) to cut according to HIS specifications, and they do. That''s a bit different than simply selecting stones and slapping a label on them.
It''s about more than just the pattern, though...it also demands superior light return and something Brian calls visual balance.
You really may want to take at look at the H&A tutorial on the WF website.
And yes, they absolutely DO reject some AGS0 diamonds for falling short of their standards. Again, not all AGS0 diamonds are H&A diamonds. If the patterning or light performance falls short of the rigid standard Brian has set for his ACAs, then the stone gets rejected....even if it''s AGS0.
That''s not quite correct. ACA stones are all AGS graded; none are GIA graded.
They aren''t simply stones bought by Whiteflash from some source. They are cut according to specific parameters at Brian Gavin''s instruction.....that is to say, he tells the cutting house(s) to cut according to HIS specifications, and they do. That''s a bit different than simply selecting stones and slapping a label on them.
Again, several incorrect pieces in these statements. ACA stones aren''t just about the hearts and arrows being more "crisp"; there are many other things involved such as uniformity of the hearts and preciseness of the pattern with nearly NO deviance from rigid standards.
It''s about more than just the pattern, though...it also demands superior light return and something Brian calls visual balance.
You really may want to take at look at the H&A tutorial on the WF website.
Absolutely incorrect. Not all AGS0 diamonds are H&A diamonds, so not all AGS0 diamonds are interchangeable.
And yes, they absolutely DO reject some AGS0 diamonds for falling short of their standards. Again, not all AGS0 diamonds are H&A diamonds. If the patterning or light performance falls short of the rigid standard Brian has set for his ACAs, then the stone gets rejected....even if it''s AGS0.
CaptAubrey
Brilliant_Rock
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Reading through all this, the aphorism about "a little knowledge is a dangerous thing" keeps running through my head.
This a very complex subject, and consumers need to be careful about thinking they know enough to be having meaningful opinions about it. That there is disagreement between the experts should tell you something.
This a very complex subject, and consumers need to be careful about thinking they know enough to be having meaningful opinions about it. That there is disagreement between the experts should tell you something.
belle
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is this a rhetorical question?
an excerpt from the wf site:
Why aren’t Hearts and Arrows photos posted for every A Cut Above diamond?
Since each ACA is so precisely cut, the H&A photos are nearly identical. A sample image conforming to our guaranteed optical symmetry is posted on each ACA page, and we will gladly take actual photos on request for consumers making an ACA purchase.
http://www.whiteflash.com/diamonds_info/t/faq.aspx?articleid=20&zoneid=6
not sure what this has to do with the original topic anyway.
I've seen the ACA cut diamonds on Whiteflash's site, they don't deviate from ideal any less than any other AGS-0 diamonds do. It's gonna be pretty rare to find an AGS-0 diamond that doesn't show pretty good hearts and arrows, about as rare as finding a diamond that fluoresces green. They may be out there, but few have seen them unless they've looked at a lot of diamonds. I'd like to know exactly what Brian Gavin has rejected an AGS-0 diamond for, because there shouldn't be any reason for him to. If the light return was that important to Whiteflash, we'd probably see them using brilliancescope like Excel Diamond does- even if the perfection of this instrument is in question you'd think he'd want stones with excellent brilliancescope scores over a stone with medium scores.
I'm not saying ACA diamonds aren't great or anything, they do a great service for online diamond shoppers. Like Eightstar, Hearts on Fire, or Superbcert you know you're getting a great diamond when you buy one. There just isn't any real difference between an ACA diamond and any other AGS-0 diamond that I know of anyway. AGS and GIA are the authorities when it comes to grading diamonds, that's why we send our diamonds to them so we know what we are getting. When you buy a branded diamond you just get another source telling you it's a great diamond as well.
belle
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what do you base this information on?
same question above regarding the reasoning for rejection.
to your question as to why he rejects them, of course the simple answer is, why don''t you ask him?
brilliancescope is not the answer for light return. as you have already pointed out, the precision (and namely repeatabliity) of the machine is questionable.
Shay37
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