H&A vs non-H&A--is there a visual difference?

[slg47]

Hi, I am hoping it is OK for interested consumers to post questions?

In RT, it is often debated if a H&A will look visibly different than a non H&A with nice numbers, good IS image, etc. I think discussion of this topic could be helpful and interesting if you experts have the time thank you

 

[Garry H (Cut Nut)]

Hi, I am hoping it is OK for interested consumers to post questions?

In RT, it is often debated if a H&A will look visibly different than a non H&A with nice numbers, good IS image, etc. I think discussion of this topic could be helpful and interesting if you experts have the time thank you

It is an excellent and often debated question SLG.

My take is that in a blind pepsi line up- if a diamond has very good optical symmetry then no one will be able to tell the difference between it and a H&A's with the same proportions etc. (without blind fold )

I have challenged several H&A's vendors to this test and they have ignored or declined.


However if a diamond is on the edge of being a little steep deep, then H&A's symmetry is a good safe indication that there will not be parts of the stone that will not sparkle enough.

Edit - consider 2 fine Quartz watches - both have the exact same accuracy, but one costs 5 times more.
And its all a mind game

 

[yssie]

Well I will get tomatoed for this I'm sure but it's 1am and I feel compelled to post anyway - I will say that I do not understand the purpose of paying the premium for a H&A I1 RB instead of choosing a well-proportioned but not precisely-optically-symmetric SI.

Inclusions *must* impact light return. Some more than others, true, and type/spread/size/placement/density all determine the degree, but I can only believe that in these lower grades they usually have far more impact on light return than the minute improvements in 'crispness' that many of our board experts describe - I personally have not been able to see this difference between my unbranded near-H&A and many, many HOFs of the same size.

 

[Garry H (Cut Nut)]

Well I will get tomatoed for this I'm sure but it's 1am and I feel compelled to post anyway - I will say that I do not understand the purpose of paying the premium for a H&A I1 RB instead of choosing a well-proportioned but not precisely-optically-symmetric SI.

Inclusions *must* impact light return. Some more than others, true, and type/spread/size/placement/density all determine the degree, but I can only believe that in these lower grades they usually have far more impact on light return than the minute improvements in 'crispness' that many of our board experts describe - I personally have not been able to see this difference between my unbranded near-H&A and many, many HOFs of the same size.

Yssie I agree, but i can also understand people who come, learn for 3 minutes and want an easy supposedly safe buy

 

[Paul-Antwerp]

Hi, I am hoping it is OK for interested consumers to post questions?

In RT, it is often debated if a H&A will look visibly different than a non H&A with nice numbers, good IS image, etc. I think discussion of this topic could be helpful and interesting if you experts have the time thank you

It is an excellent and often debated question SLG.

My take is that in a blind pepsi line up- if a diamond has very good optical symmetry then no one will be able to tell the difference between it and a H&A's with the same proportions etc. (without blind fold )

I have challenged several H&A's vendors to this test and they have ignored or declined.


However if a diamond is on the edge of being a little steep deep, then H&A's symmetry is a good safe indication that there will not be parts of the stone that will not sparkle enough.

Edit - consider 2 fine Quartz watches - both have the exact same accuracy, but one costs 5 times more.
And its all a mind game

Garry,

For the sake of completeness, could you give your definition of what is H&A for you, since you talking about a pepsi-test between a diamond with very good optical symmetry and a H&A sounds very confusing to me.

I am also sorry to see your derogatory last remark, making the comparison with quartz-watches. In how far does the remark of a 5x-cost refer to H&A-diamonds? Shame on you.

Live long,

 

[slg47]

improvements in 'crispness' that many of our board experts describe

is this crispness due to H&A or just arrows, which if I understand correctly, can be achieved without perfect hearts?

 

[Lula]

Well I will get tomatoed for this I'm sure but it's 1am and I feel compelled to post anyway - I will say that I do not understand the purpose of paying the premium for a H&A I1 RB instead of choosing a well-proportioned but not precisely-optically-symmetric SI.

Inclusions *must* impact light return. Some more than others, true, and type/spread/size/placement/density all determine the degree, but I can only believe that in these lower grades they usually have far more impact on light return than the minute improvements in 'crispness' that many of our board experts describe - I personally have not been able to see this difference between my unbranded near-H&A and many, many HOFs of the same size.

To answer your question: because I've seen 3 diamonds, ranging in clarity from VS2 to I1, from the same cutter, and there is no difference in light performance that I can detect with my eyes, after observing the diamonds in a variety of lighting conditions. So why pay for something I can't see with my eyes (higher clarity) when there is no difference in performance? It's cut consistency (which translates to superior performance) that I pay a premium for; that's the only reason to pay a premium, in my opinion. And perfect H&A doesn't necessarily guarantee cut consistency -- if I remember right, I believe HOF is an H&A brand that has been dinged on PS for its lack of cut consistency from stone to stone.

 

[yssie]

Cut consistency and vendor guarantees & warranties, and ease of choice, are very good reasons to purchase a branded stone - which usually means H&A I think, WF's ES/PS lines are the only ones I can think of that don't advertise as being H&A - even BN claims H&A though they don't provide hearts pics or actually define the term.

I simply disagree that precision of cut that yields those lovely perfect hearts makes any real-world difference in performance than a stone with a non-perfect (but pretty close) hearts pattern, and haven't seen anything to convince me otherwise. This is assuming the two stones are as similarly proportioned as possible - and have 'nice' proportions in addition to having 'good' hearts. Not going into the definitions of 'nice' and 'good' other than visibly symmetric through the viewer and stones that don't imitate sieves. The effect as I understand it described is a 'crispness', or 'sharpness in on/off' resulting from fewer tiny virtual facets that muddy the edges during a transition, but I still don't quite know what I should be searching for as I see no differences between my stone's crispness or sharpness (as, well, *I see it*) and stones with picture perfect hearts - maybe Paul will see this thread and comment.

HoF is a consistent brand from everything I've seen and heard, though their prices are outrageous..? And in any case, when you have the stone, a hearts viewer, and a sarin output in hand, the consistency of the overall brand means little.

 

[Lula]

Cut consistency is not about picture-perfect H&A, yssie -- in that respect I agree with you (in fact, I think it could be argued that Infinity diamonds don't always have the picture-perfect hearts prized on RT). Rather, cut consistency is reflected in the nature of the sparkle and scintillation that is constant from stone-to-stone within the brand. I'm sorry, but I just don't have the technical words to explain it, though I have seen it in each of my 3 stones and in the Infinity stones I saw at Dimend Scassi at last year's Meet the Cutter event. Others who have seen Infinity diamonds have remarked on this quality, so it's not just me.

My first Infinity was a VS2, then I bought an SI2, and finally, my current I1. I was able to confidently "step down" in clarity because, despite the differences in clarity grades, the characteristic appearance/performance of the Infinity diamonds remains the same from stone to stone. My own eyes (RD would be proud of me!) provided the proof and the comfort level. So I agree with what you're saying, and, in essence, this is why I am comfortable buying an Infinity diamond with such low clarity; I wouldn't choose an I1 clarity from just any brand.

I hope that helps describe what I see in layman's terms. Perhaps Paul or John Pollard can provide some technical detail about how the consistency is achieved.

I'm hoping Andelain sees this thread, because she owns two 8-stars, one of which is an I2 clarity, and the other a VS clarity, so I'd be interested to hear her perspective on owning two stones from the same brand with very different clarity grades. Does she notice a difference in performance that she can ascribe to clarity?

I think the biggest issue with SI2 and I1 grades is the sheer variety of inclusions that are found in those grades, and this makes true comparisons very difficult. The most common way is to talk about "white" inclusions versus "dark" or non-transparent conclusions, but that's still not the whole story. When I met Paul last year, he explained to me how he and Lieve work to orient the rough to minimize the effect of the inclusions on the performance of the stone. Other cutters may do this, too -- I don't know.

 

[Karl_K]

There are several levels of optical symmetry and it depends on which you are talking about:
1: H&A
2: near-h&a say with say one small heart but perfect face up optical symmetry.
3: face up optical symmetry
4: mildly face up unsymmetrical
5: face up unsymmetrical
6: very face up unsymmetrical

The rankings below are my personal opinion.

Then there are several things that need to be looked at:
A: contrast patterns - 1,2,3 will have very similar contrast patterns
B: overall light return - any of them could have as much light return as another in good lighting, in bad or marginal lighting I believe h&a can give a slight advantage.
C: fire - maybe a mild advantage to 1,2,3
D: scintillation - maybe a mild advantage to 1 and 6 (6 in a large enough diamond).
E: ratio of effective vs ineffective virtual facets across several lighting conditions. - advantage 1,2,3 in descending order.

 

[yssie]

Lula - wasn't a dig against people who choose H&A I1s. There is another regular RT poster who has an Infinity I1 and it certainly looks like a beautiful stone in her pictures. I actually agree very much on your definition of brand consistency - I haven't seen Infinities in person but they do have a characteristic 'look' in pictures.


My thoughts as a consumer -

1. despite reading many articles, threads, discussions, and talking to my jeweller (who is a HoF dealer), I am unable to see the differences that H&A are said to make in A-D in Karl's list when I compare similarly proportioned stones of similar sizes, one with very nice hearts visible through the viewer and one with slightly "problematic" hearts - say, Vs of significantly variable thickness, or asymmetrically presenting clefts, or a formation altogether missing. When comparing stones of different proportions the advantage goes to whichever stone is better suited to the given lighting - and of course, there is my own bias... I have never consistently chosen the H&A over the non-H&A in a blind test - and oh, I've tried!

Karl, your point E - effective VFs - I remember this term from a discussion about "muddy VFs" in 'crushed ice' - I confess I didn't really get it then and I don't now. Does this just mean they are capable of returning light in most lighting environments and that source and output change every few degrees so they look like they're turning 'on' and 'off' (best I could do for scintillation) - or that they are large enough that these refractions are visible to the eyes as a clear, single output - or a group of tiny VFs that because of size/proximity/angle behaves as a single plane?


2. There is just no point in saying that inclusions do not affect light return as long as the stone is eyeclean (by whatever your definition), just as there is no point in saying that body colour does not affect light return. To what extent? That, we'd likely all disagree on. That there appears to be little definable, reproducable, traceable science to clarity grading just makes it harder for us mere consumers to understand


This post, brought to you by the proud owner of a non-H&A non-eyeclean J SI2.

 

[Karl_K]

I missed my edit window the above should read:
C: fire - maybe a mild advantage to 1,2,3,4

Minor optical symmetry variations have a very min. effect on fire potential.

 

[Karl_K]

Karl, your point E - effective VFs - I remember this term from a discussion about "muddy VFs" in 'crushed ice' - I confess I didn't really get it then and I don't now. Does this mean they are capable of returning light in most lighting environments and that source and output change every few degrees so they look like they're turning 'on' and 'off' (best I could do for scintillation) - or that they are large enough that these refractions are visible to the eyes as a clear, single output - or a group of tiny VFs that because of size/proximity/angle behaves as a single plane?

Effective = capable of returning visible light to the eye in that lighting condition.
Ineffective = not capable of returning visible light to the eye in that lighting condition.
Which virtual facets are effective will vary depending on the lighting.

Small direct bright light sources are able to be reflected to the eye so they can be seen by smaller virtual facets than soft candlelight which can only be effectively returned by larger virtual facets.

 

[yssie]

Effective = capable of returning visible light to the eye in that lighting condition.
Ineffective = not capable of returning visible light to the eye in that lighting condition.

Ah. k, done & done.

 

[Paul-Antwerp]

This may sound weird, but despite there apparently being very different points of view in the posts above, I think that I can agree with every individual opinion, provided that I interpret that poster's definition of H&A correctly.

Live long,

 

[Garry H (Cut Nut)]

Hi, I am hoping it is OK for interested consumers to post questions?

In RT, it is often debated if a H&A will look visibly different than a non H&A with nice numbers, good IS image, etc. I think discussion of this topic could be helpful and interesting if you experts have the time thank you

It is an excellent and often debated question SLG.

My take is that in a blind pepsi line up- if a diamond has very good optical symmetry then no one will be able to tell the difference between it and a H&A's with the same proportions etc. (without blind fold )

I have challenged several H&A's vendors to this test and they have ignored or declined.


However if a diamond is on the edge of being a little steep deep, then H&A's symmetry is a good safe indication that there will not be parts of the stone that will not sparkle enough.

Edit - consider 2 fine Quartz watches - both have the exact same accuracy, but one costs 5 times more.
And its all a mind game

Garry,
For the sake of completeness, could you give your definition of what is H&A for you, since you talking about a pepsi-test between a diamond with very good optical symmetry and a H&A sounds very confusing to me.

I am also sorry to see your derogatory last remark, making the comparison with quartz-watches. In how far does the remark of a 5x-cost refer to H&A-diamonds? Shame on you.

Live long,

Excellent question.

I think I would be happy with the HRD system as a bench mark for H&A's - from what I have read about it Paul - but I have no real experiance with their system.

Do not be upset by my quartz movement analogy.
A $2,000 steel watch vs one for $5 from the garage is a 400 times difference. My point is there is a "mind difference" not a timie keeping difference.
Another analogy is IF vs SI1 where a 4x difference is possible and no one can see the difference with the naked eye.

 

[Paul-Antwerp]

Thank you for the clarification, Garry.

The quartz-analogy bothered me because the premiums for H&A (if existent) are far away from the multifolds of your analogy. Thus, the analogy makes no sense.

If you take HRD's H&A-system as the basis for what is H&A, I agree with your point-of-view. HRD developed a system to describe H&A from a historical perspective, not succeeding in explaining what is better. It kind of cleared up the messy definition of H&A, but it did not solve anything.

Part of this unclear definition of precision-cutting is a reason why we do not like to present our rounds as H&A. H&A is a by-product of process, not a goal in itself.

Live long,

 

[Garry H (Cut Nut)]

Thank you for the clarification, Garry.


Part of this unclear definition of precision-cutting is a reason why we do not like to present our rounds as H&A. H&A is a by-product of process, not a goal in itself.

Live long,

I agree, H&A's are a by rpoduct.
The issue I guess is how much swindling is too much. and which type - remeber Sergey and Yuri's poster at IDCC1

 

[Paul-Antwerp]

If we agree on this, Garry, you must however also consider that there are indeed observable differences (advantages) to a specific level of precision-cutting. Too many people categorize this now merely as H&A, in the absence of a definition of a higher 'precision-level', which causes a lot of misunderstandings.

To explain this in detail however, I need to take the time to explain both the history and the performance. I will get to this as soon as possible.

Live long,

 

[Paul-Antwerp]

When looking at a current situation, one may judge it on its current merits, but true understanding can only come if one also knows the history leading to the current situation. This is good advice at all times, but it also applies to the understanding of H&A, and I think it also explains why some posters here have diametrically opposing views or opinions.

First, we need to go back to the origins of H&A, dating back to the early 1990's, with a suddenly exploding demand from the Japanese market. It could be that this sudden demand was a spin-off of the local promotion of the original Eightstar-brand, reality was that the diamond-market was faced with a sudden big demand (at high prices) for H&A.

Antwerp, as the diamond-center with the biggest tradition and history in diamond-cutting, this new demand had the biggest effect. The demand also met with a group of eager diamond-cutters, since they were suffering very much under the competitive pressure of new diamond-cutting-centers.

In the absence of cutting-tools, dedicated to cutting such precision, the cutters needed to turn to their knowhow to produce for the Japanese demand. It took these first H&A-cutters really extremely long to cut the first H&A's, but it also proved very profitable because the Japanese were paying huge premiums, also because of the very limited supply.

Unlike traditional requests to cutters (cut me a VG-VG, for instance), this demand was difficult for cutters since they were faced often with new customers, not understanding exactly what the boundaries were to what they called the desired H&A, and the Japanese dealers possibly not knowing themselves, since it is unclear whether the Japanese labs also graded H&A in the beginnings of H&A. This unclear demand (as to how far can we go) combined with the non-existence of specialized tools led to the cutters working very diligently on process.

The result was that these first H&A's probably for a long time were the very best ones ever cut. Todd Gray confirmed this years ago (I read it in 1999 on the old niceice-website), that the first H&A's he saw were A-grade in his terms, while he graded all H&A's in 1999 as B-grade.

Over time, cutters learned the boundaries of the Japanese H&A-demand. Grading-labs started grading H&A in Japan. Now, grading reports generally are considered as safeguarding the consumer, but the adverse effect of grading reports is that they create a minimum-level for a certain cut-category. In cut, as soon as cutters understand the minimum-level of a cut-grade, they can switch from cutting-for-quality to cutting-for-a-grade. This is a natural phenomenon, seen regularly in the past two decades with the launch of various cut-grading-systems by various labs.

At the same time, producers of cutting-tools (including myself in a previous job) developed special precision-tools, which made the production of H&A-grades easier. Production of H&A increased because of understanding looser standards and because of new tools and was partly exported to new and cheaper cutting-centers, gradually eliminating the original cutters of H&A, especially so when the Japanese market collapsed.

The above basically explains how the quality of the original H&A-stones gradually eroded to the minimum-level of the grade, set by Japanese labs.

Remember, none of the demand for these stones was based upon any science. At best, it was a spin-off of the demand for the original Eightstars, where the science was based only on the Firescope, a tool to assess contrast-brilliance and leakage.

On today's date, this scientific basis is still missing. Labs and individual scientists are still stuck in the assessment of brilliance, and the understanding of fire and scintillation is far from being finalized, as the recent discussion in this thread (https://www.pricescope.com/forum/di...-dispersion-techy-help-please-t18987-120.html) for instance confirms.

In the meantime, HRD has also introduced a H&A-grade with a lot of documentary explanation, but it is still based upon the observation of the H&A-pattern only. Again, the minimum-level of the HRD-grade merely offers leeway to cutters.

Probably, in the same way, the PS-tutorial for H&A, based upon 'it is all in the hearts' has a similar adverse effect as a lab's cut-grade. I fully understand Brian Gavin's reasoning when presenting this (especially since the hearts-view allows better assessment of the optical symmetry), but setting the rule in stone has the same effect as the minimum-level of a cut-grade. Where the rule probably has merit when assessing a very tight production, it is also true that certain stones exhibit hearts while no arrows ('hearts only' exists, and was a secondary grade in the Japanese labs).

So, here we are, about 20 years of history of H&A and total confusion over definition, terminology and effect on observation. No wonder that everybody can be right when expressing completely opposite views.

When we started Infinity in 2001, I was influenced heavily by the comments of Todd Gray (NiceIce) about B- and A-quality in H&A, and there being no A-grade available anymore. So, I went back to how the original H&A's were cut and understood that the process of cutting was just as important as the tools-aspect. Over time, that process-part had been neglected and I relaunched it for our production. At the same time, I totally disregarded any minimum H&A-cut-grade, knowing that proper process and proper tools automatically lead to H&A, but most importantly to great looking stones.

According to me, the observation of better fire and scintillation in such precision-cut-stones is in the crispness of the stones, as can be observed in the simplified patterns of a H&A-viewer. Agreeing with me however involves rejecting ancient definitions of H&A, or at least understanding how standards and H&A-cut-grading did not help in describing cut-quality.

Live long,

 

[Garry H (Cut Nut)]

Remember, none of the demand for these stones was based upon any science. At best, it was a spin-off of the demand for the original Eightstars, where the science was based only on the Firescope, a tool to assess contrast-brilliance and leakage.

Live long,

Nice potted history Paul.
There are two comments, (but I forgot one of them) - I agree that is what the Firescope does best, but the 8* team renamed it the 'symmetry scope' and they seemed to focus very much on the symmetry aspect of what you see through it.

I agree a H&A's viewer (with decent magnification - usually absent in most available versions) is a better symmetry tool.

 

[Paul-Antwerp]

I was not sure if there was no slang involved when you mentioned 'nice potted history', Garry.

So, I looked it up and found that 'potted' means 'intoxicated by marijuana'. Now, I beg you to clarify that this was a poor choice of words.

Live long,

 

[Garry H (Cut Nut)]

I was not sure if there was no slang involved when you mentioned 'nice potted history', Garry.

So, I looked it up and found that 'potted' means 'intoxicated by marijuana'. Now, I beg you to clarify that this was a poor choice of words.

Live long,

Ha Ha Ha.
English has many odd sayings Paul.
<<briefly and superficially summarized <a dull, pedestrian potted history — Times Literary Supplement>>

http://www.amersham.org.uk/amintro.htm But that one is not brief.

 

[Paul-Antwerp]

Thank you for the clarification, Garry. I learned a new expression today.

Back to topic, is the situation of H&A possibly comparable to the performance of certain artists, where the public in the beginning of their career focuses on certain side-aspects and only after time, the artists are truly appreciated for the quality of their work? This sounds cryptic, but maybe with some examples, it becomes clearer.

For instance, Madonna, or Elvis Presley or in another field, Monty Python.

Just a thought.

Live long,

 

[WinkHPD]

Hi, I am hoping it is OK for interested consumers to post questions?

In RT, it is often debated if a H&A will look visibly different than a non H&A with nice numbers, good IS image, etc. I think discussion of this topic could be helpful and interesting if you experts have the time thank you

I hesitate to walk into this thread where Paul has given such a well considered history and overview but I would like to add one thing.

If you have a question in your mind, try to see two or more stones side by side without knowing which is which. One or more of the stones will speak loudly to you, then allow the presenter to tell which you have chosen.

It has been our experience that in most cases the better cut stones "win". Even if the viewer knows nothing about cutting, the eyes will tell them which stone they like best. In this I actually do agree with Rock Diamond.

I like to put three to five stones in a slotted tray for my in house clients without telling them anything about which stones are which or what the grades are. My experience has been that in nearly all cases the medium to well cut stones are the first to be rejected (more or less instantly!) and then the final decision is made between two or more top cut stones.

Wink

 

[Garry H (Cut Nut)]

Hi, I am hoping it is OK for interested consumers to post questions?

In RT, it is often debated if a H&A will look visibly different than a non H&A with nice numbers, good IS image, etc. I think discussion of this topic could be helpful and interesting if you experts have the time thank you

I hesitate to walk into this thread where Paul has given such a well considered history and overview but I would like to add one thing.

If you have a question in your mind, try to see two or more stones side by side without knowing which is which. One or more of the stones will speak loudly to you, then allow the presenter to tell which you have chosen.

It has been our experience that in most cases the better cut stones "win". Even if the viewer knows nothing about cutting, the eyes will tell them which stone they like best. In this I actually do agree with Rock Diamond.

I like to put three to five stones in a slotted tray for my in house clients without telling them anything about which stones are which or what the grades are. My experience has been that in nearly all cases the medium to well cut stones are the first to be rejected (more or less instantly!) and then the final decision is made between two or more top cut stones.

Wink

Hi Wink, I think everyone will agree with you.

But

Where to draw the line between each rejection and selection criteria.
Would 1,000 untrained and 1,000 trained people make the exact same selection?

What amount of table tilt would cause more than 50% of each group to reject a stone?

and on and on.

We do not even have a criteria for such a true test since we do not evn have a criteria for what would be good and what would be a sub standard H&A.

 

[WinkHPD]

Hi, I am hoping it is OK for interested consumers to post questions?

In RT, it is often debated if a H&A will look visibly different than a non H&A with nice numbers, good IS image, etc. I think discussion of this topic could be helpful and interesting if you experts have the time thank you

I hesitate to walk into this thread where Paul has given such a well considered history and overview but I would like to add one thing.

If you have a question in your mind, try to see two or more stones side by side without knowing which is which. One or more of the stones will speak loudly to you, then allow the presenter to tell which you have chosen.

It has been our experience that in most cases the better cut stones "win". Even if the viewer knows nothing about cutting, the eyes will tell them which stone they like best. In this I actually do agree with Rock Diamond.

I like to put three to five stones in a slotted tray for my in house clients without telling them anything about which stones are which or what the grades are. My experience has been that in nearly all cases the medium to well cut stones are the first to be rejected (more or less instantly!) and then the final decision is made between two or more top cut stones.

Wink

Hi Wink, I think everyone will agree with you.

But

Where to draw the line between each rejection and selection criteria.
Would 1,000 untrained and 1,000 trained people make the exact same selection?

What amount of table tilt would cause more than 50% of each group to reject a stone?

and on and on.

We do not even have a criteria for such a true test since we do not evn have a criteria for what would be good and what would be a sub standard H&A.

Garry,

You probably need to re-read Paul’s historical post.

I will say that I have the luxury of being in an easy position. It is my job to find diamonds for my customers, which they will love. So, for me, all your good questions are unimportant, since I found a production of stones that repeatedly amaze me, and more importantly, that all my customers have preferred to buy whenever they took the trouble of comparing stones directly, in real life. Problem solved in my books.

You however seem to have the desire to understand, predict and most importantly categorize what is happening in the complex interaction of human being, diamond and light. In other words, you want to understand the secrets of the chef, combined with the scientific reasons. Out of interest, I also find that nice to know, but it has nothing to do with my main task. Luckily, I do not have to know at which temperature the oven was, nor for how long, and definitely not the secret ingredient. I taste the result (in this case, see the result) and appreciate the chef.

I laud you for your efforts, though, but I do not envy you.

Wink

 

[ChunkyCushionLover]

Good question slg47 and I'm afraid the answer is complicated.

By definition Hearts and Arrows by HRD's strict definition is only obtainable from a narrow range of proportions near the classical Tolkowsky proportions (CA34.5 PA40.8 LGF74-79%). I like their strict and comprehensive system which is explained here.

There are many variations amongst these proportions(changing Star % changing LGF%) , changing slight CA and PA (eg. CA 33.5 PA 41) to name but a few things that can be different and still satisfy HRD's HA standard.

There is also asymetry and then there is ASYMMETRY the two can result in a very big appearance difference. I have seen no comprehensive (multiple lighting scenario controlled) studies that compared two diamonds such as the following example:

The same average proportions at CA34.5 and PA40.8 LGF=77%

A) crown angles 34.4 34.6 34.5 34.5 34.5 34.5 34.6 34.4
versus
B) crown angles 36.5 36 35.5 35.4 32.5 33 33.5 33.6.

There are also diamonds that would pass a hearts image test as they have near perfect cutting precision and optical symmetry but fail due to LGF% that is too short or too long. Example Eightstar(LGF=70%)

The real question should be a comparison of Near Perfect Optical Symmetry versus Near Near Perfect Optical Symmetry (not necessarily HA symmetry) does the slight difference in optical symmetry result in an discernable and observable appearance difference?

Theoretically, superior precision results in larger average virtual facets and more VFs that can be discernable by the human eye as well as more active virtual facets, but whether this translates to observable differences depends on many factors including:

Size of the diamond, viewing distance, the lighting, how big are the asymmetry differences, precision of the asymetry, the CA/PA combination, Size of the LGFs and various other proportion factors.

The CA/PA combination and length of LGF differences will have a greater impact over slight optical symmetry differences. The usual comparisons made are rarely of two diamonds that are identical thus these other factors have a greater impact than can be observed from slight differences in optical symmetry.

In order to answer your question comprehensively a non biased study and "pepsi challenge" of pairs of diamonds of the same size and average proportions would need to be compared in various carefully selected viewing environments.

I find the opinions expressed on PS over the years can be distilled down to "SuperIdeal HA Brand" vendors versus those who only sell non branded generic rounds. The former usually make comments justifying the price premium for their precision cut or carefully selected branded HA, the latter argue that the premium is not justified and their are no discernable differences.

I beleive both side can be "correct" and it really depends on which two diamonds are being compared on a case by case basis. Whether you side with either camp the greatest emphasis should still be placed on the choice of proper CA/PA and LGF combination with recognition that that grading reports information is an average of 8 values with severe rounding (especially in the case of LGF% which is in 5% increments for GIA) and no mention of precision which makes any comparisons between branded vs unbranded only a rough estimate if only comparing data from a grading report.

CCL

 

[slg47]

CCL thank you for your informative post (thanks to everyone else too, this has been a really interesting discussion and I am thankful that we have this section of Pricescope ) So CCL how do you choose the best CA/PA/LGF combination? I have heard it said sometimes that a stone that scores 2-2.5 on HCA might be OK depending on the LGF, how does LGF affect and what LGF works with what CA/PA combination? And can you even tell based on GIA report if LGF is rounded to nearest 5%? Sorry for all of the questions, if there is an article to link please do

 

[yssie]

CCL thank you for your informative post (thanks to everyone else too, this has been a really interesting discussion and I am thankful that we have this section of Pricescope ) So CCL how do you choose the best CA/PA/LGF combination? I have heard it said sometimes that a stone that scores 2-2.5 on HCA might be OK depending on the LGF, how does LGF affect and what LGF works with what CA/PA combination? And can you even tell based on GIA report if LGF is rounded to nearest 5%? Sorry for all of the questions, if there is an article to link please do

I'm not CCL, but I reckon Karl's article will answer most of the above re. lgf significance (longer="shallower"=less angle differential btwn reported mains & lower girdle facets): https://www.pricescope.com/journal/do_pavilion_mains_drive_light_return_modern_round_brilliant