Trying to understand the HCA just a little better....

[Garry H (Cut Nut)]

Date: 11/11/2005 8:39:17 AM
Author: strmrdr
Garry,
I think your proposed change in wording more accuratly reflects the visual performance of the diamonds themselves and is a good step. that is kinda funny storm because that is the old text that has been there for a very long time - I just copied and pasted it

As for the chart it looks good to me there are some areas where some combos are in slightly different places than Id put them but I dont know if its enough to matter. Happy for you tom make suggestions - or for someone who has a more advanced Adobe than my beginners student version to re do it - use the 57% I think

Its a lot to think about because there is a ton of information in just 2 stretched 0''s on a chart. Ah, if only life was simple.

 

[plg_cp]

Date: 11/11/2005 12:10:01 AM
Author: Garry H (Cut Nut)

...Your own personal preference may be for a diamond with an HCA score of 1.5 more rather than one with a lower score of say 0.5....

On a more minor note...

As someone who went through the complete newbie process fairly recently, and on behalf of novices using HCA to help them in their purchase, I would be very happy to see the above phrase reworded. I found it to be confusing and since many people incorrectly think that the lower the score the better (ie. 0.4 is much better than 1.3), I think it could use a tweak, making sure to state that essentially a score < 2 means cream of the crop.

Mark

 

[Garry H (Cut Nut)]

Date: 11/12/2005 1:47:12 AM
Author: plg_cp

Date: 11/11/2005 12:10:01 AM
Author: Garry H (Cut Nut)

...Your own personal preference may be for a diamond with an HCA score of 1.5 more rather than one with a lower score of say 0.5....

On a more minor note...

As someone who went through the complete newbie process fairly recently, and on behalf of novices using HCA to help them in their purchase, I would be very happy to see the above phrase reworded. I found it to be confusing and since many people incorrectly think that the lower the score the better (ie. 0.4 is much better than 1.3), I think it could use a tweak, making sure to state that essentially a score < 2 means cream of the crop.

Mark

Mark would this be better?
A score below 2 (red area on the chart) means the diamond is worth considering because it has an ideal proportion combination; you have eliminated most poor performers. But many people prefer diamonds with a score just above 1.0, to one with say 0.5.

 

[valeria101]

Date: 11/12/2005 1:23:22 AM
Author: Garry H (Cut Nut)

Date: 11/11/2005 8:39:17 AM
Author: strmrdr


As for the chart it looks good to me there are some areas where some combos are in slightly different places than Id put them but I dont know if its enough to matter. Happy for you tom make suggestions - or for someone who has a more advanced Adobe than my beginners student version to re do it - use the 57% I think

Is this chart going to appear anywhere aside this thread?

If so, the respective picture contains a few notions that are all but trivia, as much as I can tell. Perhaps someone who has been reading this forum for months will get it immediately, but the CutAdviser''s use is not limited to them, I hope.

It just begs the question ''what the ... are ''old people diamonds'' etc. The notes about girdle thickness and table are straightforward: all one needs to know to make sense of them is what ''girdle'' and ''table'' are and that is given on the input page of the Cut Adviser anyway. The others may need a story somewhere.

 

[strmrdr]

Date: 11/12/2005 1:23:22 AM
Author: Garry H (Cut Nut)

Date: 11/11/2005 8:39:17 AM

Author: strmrdr

Garry,

I think your proposed change in wording more accuratly reflects the visual performance of the diamonds themselves and is a good step. that is kinda funny storm because that is the old text that has been there for a very long time - I just copied and pasted it

As for the chart it looks good to me there are some areas where some combos are in slightly different places than Id put them but I dont know if its enough to matter. Happy for you tom make suggestions - or for someone who has a more advanced Adobe than my beginners student version to re do it - use the 57% I think


Its a lot to think about because there is a ton of information in just 2 stretched 0''s on a chart. Ah, if only life was simple.

what i was talking about was the proposal of adding this too it:

"The red area on this chart represents the lowest HCA scores.

Stones near the center of the red region, those with the lowest scores, are often the least affected by small symmetry variations.

A shallower stone, on the lower part of the chart, will look darker when viewed from close up, they are not for everyone. Shallow stones have the advantage of a bigger spread. They are better suited for use as pendants and earring stones where they are not usually viewed from very close proximity (a close observers head obstructs light sources that would otherwise be returned).

Deeper proportioned stones, near the upper part of the red area, have more leakage. Leakage means reduced light return. A limited amount of reduced light return can contribute to a diamonds contrast. Diamonds with a large area of partial leakage table, seen as a pale pink area with an Ideal-Scope, are best set in open backed rings so light can get in the bottom or pavilion of the diamond. It is possible for light entering the pavilion to leak back out the top as firey dispersed colored flashes. Deeper diamonds that have perfect or hearts and arrows grade symmetry, with scores around 2, will often perform far better than diamonds of lesser symmetry."

 

[strmrdr]

I think this goes a long way towards explaining some things:
From my proposed rewrite:

"Many diamonds with excellent scores may not be traditional ''ideal cuts''.
Some diamonds that score in the lower ranges may be better suited for pendants and earrings. Some cut grades do not consider these to be ideal cuts because there are better combos available for all around use. They can however be the best combos for their intended use which is why they are included in the top 5%."

I would like to see more of these diamonds on the market as long as they are properly understood and marketed.

 

[valeria101]

Date: 11/12/2005 7:08:28 AM
Author: Garry H (Cut Nut)

Date: 11/12/2005 1:47:12 AM
Author: plg_cp

Date: 11/11/2005 12:10:01 AM
Author: Garry H (Cut Nut)

...Your own personal preference may be for a diamond with an HCA score of 1.5 more rather than one with a lower score of say 0.5....

On a more minor note...

As someone who went through the complete newbie process fairly recently, and on behalf of novices using HCA to help them in their purchase, I would be very happy to see the above phrase reworded. I found it to be confusing and since many people incorrectly think that the lower the score the better (ie. 0.4 is much better than 1.3), I think it could use a tweak, making sure to state that essentially a score < 2 means cream of the crop.

Mark

Mark would this be better?
A score below 2 (red area on the chart) means the diamond is worth considering because it has an ideal proportion combination; you have eliminated most poor performers. But many people prefer diamonds with a score just above 1.0, to one with say 0.5.

A score below 2 (red area on the chart) means the diamond is worth considering because it has an ideal proportion combination; you have eliminated most poor performers. Slightly different looks among these diamonds remain a matter of taste.



I am writing this, because alternative measurements for the same diamond also cause variation of the HCA scores, and those are not a matter of preference at all. Considering that measurement error doesn't seem to be a charismatic notion

...

Besides, if the front page says 'some prefer X over Y' this invites the question why, etc. while for a composite score there is no elegant straight answer, even ignoring the previous comment. There is some amount of dead-end discussion about what exactly is the difference between the scores etc. - and that seems a bit beyond the scope of the system, as far as I understand it.

Just a thought

There's probably too much 'literature' o the issue already.

 

[Garry H (Cut Nut)]

I think the original handles Storm''s compalint better Ana

HCA grades a round diamonds cut based on only crown, pavilion and table proportions. Symmetry, polish and minor facets are not considered by HCA, but they are with GIA’s similar system which favors deeper proportion combinations. However I believe many steeper crown and deeper pavilion GIA ‘Excellent’s’ will not look great when they are dirty.

HCA should only be used as a rejection tool, to narrow down your selection of unseen diamonds. For your final selection consider using an expert appraiser or compare the diamond to other known well cut diamonds and / or view it through an ideal-scope. HCA eliminates diamonds with too much leakage or darkness, and girdles that are too thin or too thick; but there are other negative factors that HCA can’t predict.

A score below 2 (red area on the chart) means the diamond is worth considering because it has an ideal proportion combination; you have eliminated most poor performers. But many people prefer diamonds with a score just above 1.0, to one with say 0.5.

On the chart X marks the pavilion° / crown° position. The white outline shows the AGS ideal range.
Stones near the center of the red region, those with the lowest scores, are often the least affected by symmetry variations. Shallow stones, to the lower left of the chart, look darker when viewed from close up; before buying one you should examine it in different lighting. Shallow diamonds are more affected by your head obstructing light sources than a stone with proportion combinations near the upper edges of the red zone on the chart. The better your close up vision – the closer up you can look at the diamond. The closer your head, the more light sources you block, and the darker the diamond will appear. But shallow diamonds have a bigger spread, and are great for pendants and earring stones, where they are not usually viewed from very close proximity.

Deeper proportioned stones with proportion combinations in the upper green and blue zones have more leakage, which can appear as dark zones just inside the table and near the girdle; these diamonds are best set in open backed rings so light can get in the bottom or pavilion of the diamond. But small ‘vee’ shaped leakage zones near the outer edges of a diamond, as seen with an Ideal-Scope, can contribute to a diamonds contrast and brilliance.

Many hearts and arrows diamonds with excellent have HCA scores around 2. Their excellent symmetry means they will perform better than diamonds with lesser symmetry.
HCA is fine-tuned from time to time - results may change without notice.

Garry Holloway FGAA DDT

 

[valeria101]

Date: 11/12/2005 7:43:04 AM
Author: Garry H (Cut Nut)

I think the original handles Storm''s compalint better Ana

He wrote the last two posts in the same time as I was writing - didn''t see them.

It is fun for me to twist words around, perhaps too much for good measure

 

[Regular Guy]

Date: 11/12/2005 7:43:04 AM
Author: Garry H (Cut Nut)

Many hearts and arrows diamonds with excellent symmetry have HCA scores around 2. Their excellent symmetry means they will perform better than diamonds with lesser symmetry.

Garry,

Sorry for interrupting the gestalt you''re going for here...but I had been a bit puzzled by this last point. Are you saying there''s a certain type of H&A to look out for that happens to score near 2...kind of like Paul''s idea that that diamonds near an edge of measurement, just about to not be good, can actually be the best. Otherwise, why point to diamonds particularly "around 2?"

 

[Garry H (Cut Nut)]

Date: 11/12/2005 8:09:04 AM
Author: Regular Guy

Date: 11/12/2005 7:43:04 AM
Author: Garry H (Cut Nut)

Many hearts and arrows diamonds with excellent symmetry have HCA scores around 2. Their excellent symmetry means they will perform better than diamonds with lesser symmetry.

Garry,

Sorry for interrupting the gestalt you're going for here...but I had been a bit puzzled by this last point. Are you saying there's a certain type of H&A to look out for that happens to score near 2...kind of like Paul's idea that that diamonds near an edge of measurement, just about to not be good, can actually be the best. Otherwise, why point to diamonds particularly 'around 2?'

No Storm (Edit: oops, i mean Ira), I am simply saying the opposite to this:
On the chart X marks the pavilion° / crown° position. The white outline shows the AGS ideal range.
Stones near the center of the red region, those with the lowest scores, are often the least affected by symmetry variations. Shallow stones, to the lower left of the chart, look darker......

Opinions on the overall effort?
Does it work for old hands and will newbies be able to comprehend it?
Does it need more links off to explain things like this image?
Should there be the chart with ovals on it?

 

[strmrdr]

Just checked it and it looks good to me.
I think the ovals would clutter up the chart but what you might do is link a seperate page with a deaper explaination and the chart with the ovals on it and anything else you care to add.
like the image you posted above with an explaination.

 

[Garry H (Cut Nut)]

Thx Storm.
Any other comments?

Also this is the existing explanation before HCA is used - any improvements?


Holloway Cut Adviser



The Holloway Cut Adviser (patent pending) evaluates the visual appearance of a round diamond as a combination of four factors - Light Return, Fire, Scintillation and Spread.

The grading scale is: 0-2 Excellent, 2-4 Very Good, 4-6 Good, 6-8 Fair, and 8-10 Poor. Zero is almost impossible; many of the factors conflict. Most nice stones rate 1-2.

You must know Total Depth %, Table % and Crown and Pavilion angles which are on AGS reports. Rounded Crown and Pavilion %’s are given on some other reports- they are not very accurate; you should ask the vendor for the Sarin info on these and GIA graded diamonds.

The tutorial explains more about Cut and diamond beauty. A detailed description of HCA is available at www.diamond-cut.com.au.

HCA has no symmetry, polish and minor facet info; it should be used for rejecting known bad performing diamonds to narrow down your final selection. Ideal-Scope images and independent appraisers can help after that.

 

[Regular Guy]

Date: 11/12/2005 7:50:48 PM
Author: strmrdr
I think the ovals would clutter up the chart but what you might do is link a seperate page with a deaper explaination and the chart with the ovals on it and anything else you care to add.

As noted before, I agree with this.

Also, re the clarification you made for me just last, in the last paragraph, and the third to the last paragraph, where these 2 ideas are genuinely linked (i.e., for stones lowest scoring, issues of symmetry more irrelevant, and to be more assured of good performance if under 2 but close to 2, symmetry will help to increase the likelihood of that good performance)...you may consider putting those 2 ideas closer in proximity together. Or...just leave the second one out altogether, where you mention the instance of the need for symmetry at all.

 

[strmrdr]

"evaluates the visual appearance"

bugs me just a little but not sure what id change it to...

projected visual appearance?
calculated visual appearance?
potential visual appearance?

if it stays the way it is thats kewl too.

 

[Garry H (Cut Nut)]

Date: 11/12/2005 8:21:40 PM
Author: strmrdr
'evaluates the visual appearance'

bugs me just a little but not sure what id change it to...


How is this? 'evaluates the potential visual appearance'

Ira I agree it would be good to merge / join the sym comments - but can not see how to do it. Is it that important? i think the 2 kinda reinforce the idea that symmetry counts.

 

[valeria101]

Date: 11/13/2005 3:48:04 AM
Author: Garry H (Cut Nut)

Ira I agree it would be good to merge / join the sym comments - but can not see how to do it. Is it that important? i think the 2 kinda reinforce the idea that symmetry counts.

So... whay will happen to the content of this thread? Is it getting edited into a new HCA front page?

 

[Garry H (Cut Nut)]

Date: 11/13/2005 4:07:35 AM
Author: valeria101

Date: 11/13/2005 3:48:04 AM
Author: Garry H (Cut Nut)

Ira I agree it would be good to merge / join the sym comments - but can not see how to do it. Is it that important? i think the 2 kinda reinforce the idea that symmetry counts.

So... whay will happen to the content of this thread? Is it getting edited into a new HCA front page?

of course Ana

 

[Regular Guy]

Date: 11/13/2005 3:48:04 AM
Author: Garry H (Cut Nut)




Ira I agree it would be good to merge / join the sym comments - but can not see how to do it. Is it that important? i think the 2 kinda reinforce the idea that symmetry counts.

Garry, I'm not sure how important it is...but inasmuch as you're looking to tweak the text for clarity, it could be an improvement. How about just moving the second to last sentence up, as you have it presented in the forum here, up, and putting the word: "Conversely" in front of it? (More incidentally, I also modified that second idea just a bit for possible clarity).

-------------

"On the chart X marks the pavilion° / crown° position. The white outline shows the AGS ideal range.
Stones near the center of the red region, those with the lowest scores, are often the least affected by symmetry variations. Conversely, should hearts and arrows diamonds with excellent symmetry have HCA scores around 2, because of their excellent symmetry, they will perform better than diamonds with lesser symmetry.

Shallow stones, to the lower left of the chart, look darker when viewed from close up; before buying one you should examine it in different lighting. Shallow diamonds are more affected by your head obstructing light sources than a stone with proportion combinations near the upper edges of the red zone on the chart. The better your close up vision – the closer up you can look at the diamond. The closer your head, the more light sources you block, and the darker the diamond will appear. But shallow diamonds have a bigger spread, and are great for pendants and earring stones, where they are not usually viewed from very close proximity."

-----------------

I think the other change I made is to return the paragraph separations to be the same as you have it now, when you open the HCA tool up. This way, rather than merging in one paragraph both ideas of symmetry benefits/consequences of HCA numbers with issues of shallow stone performance, you keep those ideas separate, too.

Just some ideas.

 

[strmrdr]

Date: 11/13/2005 3:48:04 AM
Author: Garry H (Cut Nut)

Date: 11/12/2005 8:21:40 PM

Author: strmrdr

''evaluates the visual appearance''


bugs me just a little but not sure what id change it to...



How is this? ''evaluates the potential visual appearance''

Ira I agree it would be good to merge / join the sym comments - but can not see how to do it. Is it that important? i think the 2 kinda reinforce the idea that symmetry counts.

''evaluates the potential visual appearance'' sounds good to me :}

 

[Rhino]

Hi all,

Love to see the teamwork that is happening here as this will ultimately help all consumers in the long run who consult the HCA and seek advice from this forum. I haven''t had the time to address some of the things brought up in this thread which Garry has asked my input on but I did want to clarify some things and answer some of the questions that were put forth to me personally as they were some good questions.

Date: 11/10/2005 3:29:47 AM
Author: belle

actually, forget scores under 2.0 and the top 5% for now and answer me this.. what would be the term you would use for the group of stones (as a whole) that are currently graded as either ags ideal or gia excellent?
would you call those ideal?

I''d call em lab graded ideals.

what about all of the stones that were graded as ideal under the old ags system that is still being used today? are those ideal?

I''d call em old ideals.

Are they ideal now? Many of them would still be considered such under the new system but admittedly there are many that would not be. I know of factories in this trade belle who were cutting the heaviest ideals they could (and there are many of them) whose entire inventories, HAD to go back to production and be recut in order to get the new ideal grade. That''s one reason why the new cut systems are getting under the skin of some supply houses.

what about that stone that not yet graded stone that looks like, according to facetware, will grade as ''excellent'' come january?
is it ideal?

With a knowledge of the upper girdles it surely can and will be. Ie. if a stone checks out fine on FacetWare, or is scanned on a Sarin with the FacetWare plug in and the gemologist has confirmed that painting/digging is either absent of at the very least minimal, yes it will get GIA''s top grade. Good questions.

what if that disclaimer on facetware was right and the stone only graded as ''very good'' is it now out as ideal?

Absolutely. That is the one limitation of FacetWare that folks need to know about. Facetware does not account for the painting/digging we were discussing in the other thread which does in fact impact face up appearance. Too much painting and digging in either case, even if the stone checks out fine on FacetWare will impact the optical performance of the diamond and cause it to not get an ideal grade, hence the disclaimer.

no one has said or even suggested that stones scoring under 2.0 would be (according to the most recent advances in cut grading) ags ideal or gia excellent or even implied it. that would be especially difficult since both systems have been/are currently changing their cut grading system. so please don''t suggest that only stones with the right document at the right time are the only ones that can be considered ideal because the bottom line is, the term ''ideal'' is widely applied and accepted in this industry, but it seems to at least have the most appropriate place here.

Hrm... please don''t take this in the wrong spirit belle because I''m not here to argue but who was the one who suggested to newbies that "as long as a diamond scores under a 2 on the HCA it is ideal."?

Regarding the use of the term "ideal", it really isn''t so wide spread use in the industry as you might think. It may be on this forum but in the industry as a whole it isn''t and when I hear a manufacturer say "This is an "ideal" diamond", my first question to hiim is how does he know because I''m not going to tell a client that a stone is ideal unless it actually meets those requirements. AGS is the only firm that uses it and we are careful to only use the term on diamonds whose proportions meet those standards. If we can''t confirm that I don''t go anywhere near the term. To suggest a diamond is ideal when it in fact is not is misleading. I''m sure you would agree. This is the entire point of what I was trying to say in the other thread. That is all.

Date: 11/9/2005 11:42:55 PM
Author: Rhino

I believe it is a good ''pre-sorting'' tool if indeed you know what it is you are sorting for. This involves learning client preferences and needs.

tell me you didn''t really mean this.
you are implying that the average person cannot properly use the hca for himself and that only those who ''learn client
preferences and needs'' (indicating a vendor) are qualified to interpret it.

Absolutely. As a professional in this trade who is probably more familiar with reflector technology and the HCA than most I mean it with all my heart. I am glad to see the progress that has been made in this thread regarding the verbatim to be used on the HCA home page. I would never counsel a client to just go to the HCA and find a stone. I would never counsel that he not investigate or know the score of course but quite frankly, while I respect all of the work Garry has done to develope the HCA, I don''t use it at all. Sometimes I''m curious to see scores on certain stones but really, that''s the extent of it. One point I think needs to be mentioned is this as well. It has been said repeatedly that the HCA is a tool for rejection and not selection which raises the question ...

When you have eliminated a pool of diamonds to be rejected ... what pool remains? Answer: The one for selection.

It is here where some folks may be getting confused and it should be stressed that even amongst the pool for selection, there are some poor combos here that should have been tossed with the other 95% in the opinions of many professionals. Some whom I would disagree with as well because there are certain lighting environments in which all stones under a 2 on the HCA appear just fine in but then there are other important environments in which they do not. I hope you see where I''m coming from on this belle. I am not against anyone using the HCA. I would always encourage a consumer to get as much knowledge and information they can before they plunk down the ching. I''m just for consumers knowing and understanding its limitations. Can we agree this is a good thing?

Kind regards,

 

[Rhino]

Date: 11/10/2005 7:28:40 PM
Author: aljdewey

Date: 11/10/2005 4:01:03 PM
Author: Rhino


This raises the question: First round of elimination for what? Ideal cuts? Please clarify.

I''ve done so multiple times already.....and in English, too....but ok. To eliminate diamonds with number relationships that suggest the diamond is likely to be a POOR performer. NOT to eliminate diamonds to the point where the only remaining diamonds will fit into AGS0 or GIAIdeal criteria.

Poor performer according to whom?

Got a newsflash for ya.....some people are fine with AGS1 stones. Some like AGS2. While they aren''t AGS0, they still outperform a damn huge percentage of all available stones in the marketplace, right?

Is this a question or a statement? If given the choice I''d take a shallow stone over a deep one in most circumstances however this is not the point. The point is if a consumer is going to consult the HCA they should know before even using it what they are and aren''t weeding out. The consumer who uses it is led to believe they are finding ideal cuts, even selected better than the old AGS standards. I see the verbatim has been taken down at this moment but the old comments were to that effect. I agree, client preference may indeed be for an AGS 1 or 2 but they do not know that from the get go. I am for people knowing and understanding these things before they consult it. That is all.

GET OFF the ''ideal'' terminology. That''s your problem. You keep wanting everyone else to conform to wanting the ''creme de la creme''......not everyone wants that, and not everyone needs that. You keep wanting to limit discussion to ONLY AGS0 or GIA-Ideal possibilities.

Ahem... I was not the one who introduced the "ideal" terminology and applied it to the HCA. Wow ... I realize you still didn''t understand this from that last thread. After having read through that again and this comment I now know beyond a shadow of a doubt where the misunderstanding lies. We can discuss this privately if you like. As a matter of fact I''d like to, to clear the air and this misunderstanding. I will not address the rest of this post of yours addressing HCA and "ideal" because you seem to be a little confused on why I''m even addressing this. You are mistaken about my reason for writing what I am and I now see you don''t understand why I was participating in the other thread. I know why you think I was but you have misjudged me Alj.

Date: 11/10/2005 4:01:03 PM
Author: Rhino

Good analogy and good point. Answer: Enough of a difference that the 2 most conservative labs don''t consider many of these under HCA <2 combinations to be ideal. That''s enough for most consumers to know.

No, it''s not enough for consumers to know. The big piece you''re missing here is what the CONSUMER can perceive as a difference.

Rich Sherwood made a VERY sage statement a few months back: ''What is true ''by definition'' is not necessarily observable ''in practice''. It makes no difference to a person that a bullet drops six inches at a thousand yards when it has been fired at him from six feet. The nuance of the physics escapes him.''

Look, I''m sure AGS and GIA can readily spot the nuances between a VS1 and a VS2......but *I* can''t, and most Joe Average Consumers can''t. I''m sure they can readily appreciate minute differences in light performance......but *I* can''t, and most Joe Average Consumers can''t. People at labs spend YEARS looking at thousands of stones.......they are experts. OF COURSE they are more likely to see infinitessimal differences. But that DOESN''T mean AVERAGE consumers will see them.

I just spent FIVE HOURS at Whiteflash last month; so did Mara. Faced with a wide array of stones, *we* couldn''t tell which stones were H&A and which were just shy of it. We couldn''t tell which stones were shallow pavilion angles and which weren''t. We couldn''t tell which stones had crowns over 35 and which didn''t. We couldn''t even ascertain with certainty which stones were which colors when all lined up in the tray.

Now, it''s possible that Brian, you, Garry, Dave, every member of AGS and every member of GIA could appreciate *some* minute performance differences.......but most consumers won''t be able to see such subtle differences.

To be clear then ... are you suggesting that consumers can not see differences between all stones that fall under a 2 on the HCA? I agree 110% with your statement "The big piece you''re missing here is what the CONSUMER can perceive as a difference."

Except for the fact that I don''t believe, for a moment that I am missing anything regarding this piece to the puzzle.

I have been standing at the counter for years helping folks, comparing diamonds not to mention all the stones we ship out. Alj... I am talking about differences the consumer can easily see with their own 2 eyes. No scopes, no technologies, no viewers, no nothing except their own 2 eyes. Based on what you have said above I''m willing to bet most stones you looked at were all H&A types with only minor nuances in certain areas which are barely noticeable and with that I''d give nothing but a hearty AMEN! WF carries a particular flavor of H&A and most of them if not all are virtually the same. I''m not sure if you got to compare a 75% lower half next to an 80% or 85% and how this impacts the optical properties. I only know from Mara''s other post that you did at least get to compare painted vs classic girdle types and that is good! Mara pointed out the optical effects she saw and is good observation. It concurs with what we see in our lab, what Leila has seen and others who have pm''d me in hte trade who have made these same observations. What do you know? We''re on the same page.

However do you still think that all stones under 2 on the HCA have such minor nuances that the average Joe Consumer can not see the differences?

I am interested to hear your answer to this. I am only looking to help your understanding of these matters and the rest of the PS team so we can all better help newbies who come to this forum.

Jonathan

 

[Rhino]

Date: 11/12/2005 1:47:12 AM
Author: plg_cp

Date: 11/11/2005 12:10:01 AM
Author: Garry H (Cut Nut)

...Your own personal preference may be for a diamond with an HCA score of 1.5 more rather than one with a lower score of say 0.5....

On a more minor note...

As someone who went through the complete newbie process fairly recently, and on behalf of novices using HCA to help them in their purchase, I would be very happy to see the above phrase reworded. I found it to be confusing and since many people incorrectly think that the lower the score the better (ie. 0.4 is much better than 1.3), I think it could use a tweak, making sure to state that essentially a score < 2 means cream of the crop.

Mark

Thank you for this input Mark because as a recent newbie (and all newbies out there) this is the most valuable and important input to this thread. It is precisely this confusion I would like to see eliminated as well and I am sure you will see excellent clarification in the next update.

Be aware that all of the folks here (including those who appear to take issue with me) have your best interests in mind and in no way are seeking to lead you astray. There is a good team playing here, just a few misunderstandings. Welcome to the human race eh?

Kind regards,

 

[plg_cp]

Date: 11/12/2005 7:30:50 AM
Author: valeria101

Date: 11/12/2005 7:08:28 AM
Author: Garry H (Cut Nut)

Date: 11/12/2005 1:47:12 AM

Author: plg_cp
On a more minor note...

As someone who went through the complete newbie process fairly recently, and on behalf of novices using HCA to help them in their purchase, I would be very happy to see the above phrase reworded. I found it to be confusing and since many people incorrectly think that the lower the score the better (ie. 0.4 is much better than 1.3), I think it could use a tweak, making sure to state that essentially a score < 2 means cream of the crop.


Mark

Mark would this be better?

A score below 2 (red area on the chart) means the diamond is worth considering because it has an ideal proportion combination; you have eliminated most poor performers. But many people prefer diamonds with a score just above 1.0, to one with say 0.5.

A score below 2 (red area on the chart) means the diamond is worth considering because it has an ideal proportion combination; you have eliminated most poor performers. Slightly different looks among these diamonds remain a matter of taste.

Garry,
Yes, in my opinion your revision is much clearer. I see that Ana has made a tweak to it and I must admit I don''t understand the rationale she wrote for it.

To me, "But many people prefer diamonds with a score just above 1.0, to one with say 0.5." is a fairly important phrase to have in.

Mark

 

[Rhino]

Date: 11/13/2005 7:16:44 PM
Author: plg_cp

Date: 11/12/2005 7:30:50 AM
Author: valeria101

Date: 11/12/2005 7:08:28 AM
Author: Garry H (Cut Nut)

Date: 11/12/2005 1:47:12 AM

Author: plg_cp
On a more minor note...

As someone who went through the complete newbie process fairly recently, and on behalf of novices using HCA to help them in their purchase, I would be very happy to see the above phrase reworded. I found it to be confusing and since many people incorrectly think that the lower the score the better (ie. 0.4 is much better than 1.3), I think it could use a tweak, making sure to state that essentially a score < 2 means cream of the crop.


Mark

Mark would this be better?

A score below 2 (red area on the chart) means the diamond is worth considering because it has an ideal proportion combination; you have eliminated most poor performers. But many people prefer diamonds with a score just above 1.0, to one with say 0.5.

A score below 2 (red area on the chart) means the diamond is worth considering because it has an ideal proportion combination; you have eliminated most poor performers. Slightly different looks among these diamonds remain a matter of taste.

Garry,
Yes, in my opinion your revision is much clearer. I see that Ana has made a tweak to it and I must admit I don''t understand the rationale she wrote for it.

To me, ''But many people prefer diamonds with a score just above 1.0, to one with say 0.5.'' is a fairly important phrase to have in.

Mark

Garry,

It would be my recommendation to avoid use of the term ideal altogether in the nomenclature becaues it only defines one person''s and only one person''s personal interpretation of it according to the use of this tool becaues not all of these crown/pavilion combinations produce ideal diamonds. I can easily understand how folks are getting confused here and belle''s use of the term in the other thread. If you''re going to use the term "ideal" then I would suggest this alteration to the above statement...

A score below 2 (red area on the chart) means the diamond is worth considering because it indicates that the majority of facets are functioning as reflectors as opposed to leakers. While not identifying "ideal cuts" according to the most conservative labs, it does indicate many ideal proportion combinations and you have eliminated most poor performers. Notable to Slightly different looks among these diamonds remain a matter of taste and not all stones will appear the same in all lighting environments. It is highly recommended you seek the consultation of a professional after gaining the information from this tool to help determine, in finer detail your personal visual preferences.

This would be accurate. What do you think?

 

[strmrdr]

going to have to disagree with you a bit rhino:

"indicates that the majority of facets are functioning as reflectors as opposed to leakers."

The hca does not tell you that, an IS image does.
for example a stone with an average of 40.9 but a range of 40.6 to 41.5

The hca tells you mainly that the average crown angle works well with the average pavilion angle.

Paul would say when cutting to the edge like he does, that what is in the average can be more important than the average.

 

[Garry H (Cut Nut)]

Thanks again Mark

Date: 11/13/2005 7:49:28 PM
Author: Rhino

Garry,

It would be my recommendation to avoid use of the term ideal altogether in the nomenclature becaues it only defines one person''s and only one person''s personal interpretation of it according to the use of this tool becaues not all of these crown/pavilion combinations produce ideal diamonds. I can easily understand how folks are getting confused here and belle''s use of the term in the other thread. If you''re going to use the term ''ideal'' then I would suggest this alteration to the above statement... Rhino I have not used "ideal" for a long time - the only reference i generally make is in the terms BIC, TIC and FIC - and that is another matter that is not actually covered on ''this'' page.

A score below 2 (red area on the chart) means the diamond is worth considering because it indicates that the majority of facets are functioning as reflectors as opposed to leakers. While not identifying ''ideal cuts'' according to the most conservative labs, it does indicate many ideal proportion combinations and you have eliminated most poor performers. Notable to Slightly different looks among these diamonds remain a matter of taste and not all stones will appear the same in all lighting environments. It is highly recommended you seek the consultation of a professional after gaining the information from this tool to help determine, in finer detail your personal visual preferences.
With due respect - it is getting far too wordy - we want essential info, and not a complete tutorial - otherwise people will not read it. it is already too long I fear.

This would be accurate. What do you think?

Thanks everyone
will try to put an end to it tonight and give it to Leonid to put up.

 

[Rhino]

Date: 11/13/2005 11:22:03 PM
Author: strmrdr
going to have to disagree with you a bit rhino:

''indicates that the majority of facets are functioning as reflectors as opposed to leakers.''

The hca does not tell you that, an IS image does.
for example a stone with an average of 40.9 but a range of 40.6 to 41.5

The hca tells you mainly that the average crown angle works well with the average pavilion angle.

Paul would say when cutting to the edge like he does, that what is in the average can be more important than the average.

I hear your point. Think about it though ... Garry devised the HCA using what? The mother to the IS.

We know for a fact it does indeed eliminate what? Stones with excessive leakage eh? I know there are stones out there with wild variances but at least with a good average pavilion angle at least a good portion of them will be functioning as reflectors. Bear in mind its not perfect just as any technology isn''t perfect. I don''t think that''s the goal here. But at least with good averages it puts a person in the ball park of having a stone wherein the predominant majority of facets are functioning as reflectors. That is a good ball park to be in for starters I would say. If the HCA was going to take into account variances then a whole lot more information would be needed and the HCA is not designed to do this (neither is GIA''s FacerWare for that matter). For the simplistic purposes the HCA was designed for, while I like your idea of *knowing the variances*, I''d leave that for 2nd/3rd round considerations for those who would want to know or care.

What do you think? Does that sound reasonable?

 

[Garry H (Cut Nut)]

OK, I tried to reduce the # of words and keep it as an easy read
Starting with the pre warning

Holloway Cut Adviser


The Holloway Cut Adviser (patent pending) estimates a round diamonds appeal based on its potential Light Return, Fire, Scintillation and Spread.

Most people prefer stones that rate 1-2 on a scale where: 0-2 Excellent, 2-4 Very Good, 4-6 Good, 6-8 Fair, and 8-10 Poor. Zero is almost impossible since many of the factors conflict.

You need Total Depth %, Table % and Crown° and Pavilion° angles from AGS and 2006 GIA and IGI reports. Using rounded Crown % and Pavilion %’s is less accurate, if a stone scores under 2.0, ask the vendor for a Helium, Sarin or Ogi report with angles.
Because HCA gets no symmetry, polish and minor facets info please only use it to reject likely bad performing diamonds & narrow down your final selection. Ideal-Scope images and independent appraisers can help after that.

The tutorial explains more about Cut and diamond beauty. More about HCA at www.diamond-cut.com.au.

Now this is the warning that appears after result:

Only use HCA to reject diamonds & narrow down your selection. GIA’s new system is similar to HCA, but adds symmetry, polish and minor facet info. Steeper crown and deeper pavilion combination GIA ‘Excellent’s’ may not look good when dirty.

Consider using an expert appraiser for your final selection, or compare the stone to other well cut diamonds and / or view it through an ideal-scope. A score below 2 (red on the chart) means you have eliminated most diamonds with too much leakage or darkness, overly thin or thick girdles & fish-eyes. But there are other negatives that HCA can’t predict. Many people prefer diamonds with a score between 1.0 and 2.0, to shallower stones around 0.5.

Shallow stones (lower left on the chart) may look darker than stones with proportions in the upper edges of the red zone. The better your close up vision, the closer your head, and the more light sources you obstruct; the diamond appears darker. But shallow diamonds have a bigger spread, and are great for pendants and earrings, where normal social viewing distances apply.

Stones near the center of the red region (the lowest scores) are least affected by symmetry variations. Alternatively hearts and arrows diamonds, which have excellent optical symmetry, but often HCA scores around 2, may out-perform diamonds with lesser symmetry and lower HCA scores.

Deeper stones in the upper green and blue zones have more leakage and often appear dark just inside the table and the outer girdle edges; they are best set in open backed rings so light can get in the bottom or pavilion. But small ‘vee’ shaped leakage zones near the outer edges of a diamond, as seen with an Ideal-Scope, can add to a diamonds contrast and brilliance.

The ‘X’ on the chart marks the pavilion° / crown° position. The white outline shows the AGS ideal candidates range. HCA is fine-tuned from time to time - results may change without notice.

Garry Holloway FGAA DDT

 

[valeria101]

Date: 11/13/2005 7:16:44 PM
Author: plg_cp

I see that Ana has made a tweak to it and I must admit I don''t understand the rationale she wrote for it.

Because... how and where is it explained what is the difference between Diamonds scoring below 1 and those scoring between 1 and 2? Initially, the 0-2 interval is given as a way to ''eliminate poor performers'' - so that everything in it has a common property, but what exactly is there to choose between in this interval? You may or may not agree with me that the HCA is not put to good use to make finer cuts like that.


Another reason are cases like THIS

For this one as well as a a good slice of the database where it comes from, there are both AGS and SARIN reports. The HCA with AGS data gives score 0.8, and the Sarin numbers 1.4 etc. So... which diamond to choose here?