round brilliant purchase - idealscope?

[gmanesq]

what if the H&A are not good or if there are no H&A at all? Any result in light performance or beauty of the diamond?

 

[starryeyed]

what if the H&A are not good or if there are no H&A at all? Any result in light performance or beauty of the diamond?

gmanesq, you are looking for black and white answers where there is a lot of gray. I don't want to sound cliched, but the beauty of the diamond is in the eye of the beholder.

H&A is a slippery slope. You can certainly have a diamond that is not a branded H&A that has great light performance and is very beautiful. So you wonder about the converse - you see a beautiful diamond and you wonder if it displays H&A. Look through the H&A viewer.

Have you gotten an IdealScope yet? That will help you as you look at these stones.

 

[yssie]

My question remains, do you have to have hearts and arrows to have a beautiful diamond?

There are many threads arguing both sides.

For an RB my opinion is no.


The precision of cutting that creates perfectly symmetric hearts (and I'm including modified hearts in this statement) requires much more time and effort than just getting the proportions "right" on target.

The high optical symmetry results in larger avg virtual facet size, and the larger the virtual facet the greater the capability for pronounced and uninterfered-with light refractions & dispersions - this is part of why princesses and rounds of the same face-up area have very different "types" of performance. If you're looking for big, bold flashes and blocks of colour, having larger virtual facets will enable this type of light return.

However, in the real world, the difference between a round with perfect optical symmetry and a round of similar proportions without is going to be far less than the difference two rounds with different lower half lengths, different crown/pavilion combos.. The price difference between a well-proportioned "near H&A" and a "true H&A" is significant, the appearance and performance will be IMO 99.9% indistinguishable.

So.. is it important? Lots of people think so, and are willing to pay the premium for it. Lots of people don't.

Yssie,

You are mixing up two separate issues.

If we are talking about precision-cutting as to pattern and crispness of that pattern (I am not fond of the H&A-term myself), it is correct that a higher precision and optical symmetry generally leads to less and thus larger virtual facets. However, most important is the opposite: less precise and less optically symmetrical cutting leads to extra tiny virtual facets that take away from the potential crisp on/off-effect of scintillation.

This as such cannot be compared to the difference in number and size of virtual facets caused by changing lower half lengths.

Live long,

I am not comparing the phenomena, I am stating that the visual difference between StoneA that is "true H&A" of x/y/z proportion combo and StoneB that is a "near-H&A" of x/y/z proportion combo will be far less obvious than the visual difference between StoneC that has lgf70 and StoneD that has lgf80

 

[gmanesq]

These jewelers are bringing in ideal scopes for me. One has the light path and ideal scope already. The other jeweler is bringing it in from his other store. I hope this helps the process.

 

[yssie]

Ditto.

people refer to "perfect hearts & arrows", but what if there are no hearts and arrows at all?
I specified "near H&A" for exactly this reason - some people do not like the 'organized' look of arrows, and prefer a completely random pattern. GIA does not consider hearts when grading, but to get a very random pattern the physical (facet meet-point) symmetry must also be non-perfect, which will lower the symmetry grade given - which is fine, if that's the look you like!

Just wanted to add that to get no pattern, the symm grade would need to drop, probably to a G, and then GIA will down grade the cut grade to a grade above the symm grade.

I have no idea what this assessment is based upon, and strongly disagree. I see no necessary connection between the lab-graded symmetry-grade (physical symmetry) and the absence of pattern. Yssie and SC, I think that you are both off.

Live long,

Either its miscommunication or misconception, but Paul is right, you can have Excellent meet point and "external" symmetry, which is what GIA grades on their report and still not come close to hearts and arrows optical symmetry. (very common)
This, yes

You can also have hearts and arrows optical symmetry and still get meet point symmetry of very good (much much less common).
Do you mean very good in the general sense or very good as a gia symmetry grade?

How is it possible to form excellent optical symmetry with with poor meet-point symmetry?

Can you add a link/example here?

THIS ARTICLE: http://www.gia.edu/diamondcut/pdf/polish_and_symmetry.pdf describes symmetry as GIA grades it.. with nifty diagram examples of what sorts of things GIA will downgrade symmetry for. If the table is off-centre, no perfect arrows. If the culet is off-centre, no perfect hearts. If the eight sections of diamond aren't all exactly equal (main sizes are different & assymetric, star facets are different/assymetric, upper girdle facets are different/assymetric), no perfect hearts because the pavilion mains and pavilion halves are of different sizes/at different angles to each other, and no perfect arrows made opposite each other at the same time (going by the method of cutting H&A as described in THIS ARTICLE: http://www.wtocd.be/DiamondInfo/articlesPDF/Article4_Formation_of_HA.pdf)
As I understand to create the phenomenon of optical symmetry that manifests as perfect hearts, one is still cutting the physical stone and working with the given physical dimensions, and if the physical dimensions are off enough there's nothing to work with..

Where's the disconnect?

 

[yssie]

Ditto.

people refer to "perfect hearts & arrows", but what if there are no hearts and arrows at all?
I specified "near H&A" for exactly this reason - some people do not like the 'organized' look of arrows, and prefer a completely random pattern. GIA does not consider hearts when grading, but to get a very random pattern the physical (facet meet-point) symmetry must also be non-perfect, which will lower the symmetry grade given - which is fine, if that's the look you like!

Just wanted to add that to get no pattern, the symm grade would need to drop, probably to a G, and then GIA will down grade the cut grade to a grade above the symm grade.

I have no idea what this assessment is based upon, and strongly disagree. I see no necessary connection between the lab-graded symmetry-grade (physical symmetry) and the absence of pattern. Yssie and SC, I think that you are both off.

Live long,

Either its miscommunication or misconception, but Paul is right, you can have Excellent meet point and "external" symmetry, which is what GIA grades on their report and still not come close to hearts and arrows optical symmetry. (very common)
This, yes

You can also have hearts and arrows optical symmetry and still get meet point symmetry of very good (much much less common).
Do you mean very good in the general sense or very good as a gia symmetry grade?
I have started a new thread in Diamond Research and would love to discuss further outside OP's thread.

 

[Paul-Antwerp]

My question remains, do you have to have hearts and arrows to have a beautiful diamond?

There are many threads arguing both sides.

For an RB my opinion is no.


The precision of cutting that creates perfectly symmetric hearts (and I'm including modified hearts in this statement) requires much more time and effort than just getting the proportions "right" on target.

The high optical symmetry results in larger avg virtual facet size, and the larger the virtual facet the greater the capability for pronounced and uninterfered-with light refractions & dispersions - this is part of why princesses and rounds of the same face-up area have very different "types" of performance. If you're looking for big, bold flashes and blocks of colour, having larger virtual facets will enable this type of light return.

However, in the real world, the difference between a round with perfect optical symmetry and a round of similar proportions without is going to be far less than the difference two rounds with different lower half lengths, different crown/pavilion combos.. The price difference between a well-proportioned "near H&A" and a "true H&A" is significant, the appearance and performance will be IMO 99.9% indistinguishable.

So.. is it important? Lots of people think so, and are willing to pay the premium for it. Lots of people don't.

Yssie,

You are mixing up two separate issues.

If we are talking about precision-cutting as to pattern and crispness of that pattern (I am not fond of the H&A-term myself), it is correct that a higher precision and optical symmetry generally leads to less and thus larger virtual facets. However, most important is the opposite: less precise and less optically symmetrical cutting leads to extra tiny virtual facets that take away from the potential crisp on/off-effect of scintillation.

This as such cannot be compared to the difference in number and size of virtual facets caused by changing lower half lengths.

Live long,

I am not comparing the phenomena, I am stating that the visual difference between StoneA that is "true H&A" of x/y/z proportion combo and StoneB that is a "near-H&A" of x/y/z proportion combo will be far less obvious than the visual difference between StoneC that has lgf70 and StoneD that has lgf80

I am sorry, Yssie, but you missed my point.

In the highlighted paragraph, if you are talking about big, bold flashes, you are talking more about the difference a shorter LGF makes, and not about the true benefits of precision-cutting. In that sense, it does not explain the benefit of a crisp pattern.

Logically, this ends in a comparison that I feel is incorrect. The disconnect is in the start of your reasoning.

Live long,

 

[starryeyed]

These jewelers are bringing in ideal scopes for me. One has the light path and ideal scope already. The other jeweler is bringing it in from his other store. I hope this helps the process.

Just wondering, do you know what a "good" IS image looks like vs. an undesirable one? Check out this article:
https://www.pricescope.com/tools/ideal-scope

and this chart: http://www.ideal-scope.com/1.using_reference_chart.asp

Let us know how it goes!

 

[gmanesq]

I went to one of the jewelers that brought in a 2.14 ct round. It is GIA triple EX H, SI1. It was pretty clean and was very nice.

Here are the numbers:

table 58%, depth 61.1%, 34 degrees, 41.4 degrees, 14% and 43.5%

When I do the HCA with the degrees it only comes out as good and very good. However when I do the HCA with the %'s, it comes out as very good and excellent.

Why does this happen?

which should i be using to calculate with HCA? Is one more accurate than the other?

 

[starryeyed]

I went to one of the jewelers that brought in a 2.14 ct round. It is GIA triple EX H, SI1. It was pretty clean and was very nice.

Here are the numbers:

table 58%, depth 61.1%, 34 degrees, 41.4 degrees, 14% and 43.5%

When I do the HCA with the degrees it only comes out as good and very good. However when I do the HCA with the %'s, it comes out as very good and excellent.

Why does this happen?

which should i be using to calculate with HCA? Is one more accurate than the other?

Directly from the HCA tool page:

"Angles vs. Percent for Crown and Pavilion

It is best to input crown and pavilion angles into HCA to reject less beautiful diamonds. We use trigonometry to calculate the angles from % data. Use angles if you have them because:
%'s are often rounded i.e. 13.3% crown height becomes 13% or 13.5%.
Pavilion depth % when converted to pavilion angle often understates the pavilion angle by 0.15 deg
Scanners are not good at measuring culets; a culet reduces the pavilion depth % but does not change the pavilion angle.
Sarin scanner data is better than Ogi because they calculate the angles and then scale of the %'s. Ogi works the other way round."

 

[gmanesq]

when using angles in the HCA this is the result:

Light Return Good
Fire Good
Scintillation Good
Spread
or diameter for weight Very Good

Total Visual Performance 4.6 - Good - Only if price is your main criterion

when using % in HCA this is the result:

Light Return Excellent
Fire Excellent
Scintillation Very Good
Spread
or diameter for weight Very Good
Total Visual Performance 1.5 - Excellent
within TIC range


According to what you said, I should go by the 4.6 score. Although the ring looked good, I am skeptical because of this score and the disparity between the results using % and angles.

in general, should I just use angles or try to get excellent with both?

 

[Garry H (Cut Nut)]

4.6 - yes