Adding Symmetry to HCA scores

[Garry H (Cut Nut)]

I would like opinions on adding a symmetry score to HCA.

Bonus for H&A X%, AGS Ideal Y%, Excellent Z%
No bonus for VG 0%
Penalty for Good, Fair and Poor

We are in Beta testing for an addition to HCA that indicates how big or small a round diamond looks like. Not just it's dimension relative to its carat weight, but an estimate taking into account peripheral light leakage. This will be called Holloway Cut Adviser Looks Like or HCA LL.
Part of the new data entry is symmetry. So it will be easy to add bonus and penalty to HCA (many people already seem to accept H&A's up to HCA 2.5).
Of course dimensions and carat weight are also part of the new data requirements.
As soon as practical we will also allow entry of any AGS or GIA report number - regulars already know that many report #'s already work this way.

 

[Athena10X]

Since most reports do not grade for optical symmetry, just meet point symmetry, could the proposed version penalize potential unbranded H&A stones, especially since not all vendors provide H&A images for virtual inventory (hard enough to get IS and/or ASET). Im thinking the update may automatically make branded super-ideals far superior, while there may be comparable stones just as decent even amongst AGS Ideal and GIAXXX. Could this be an additional option for those who are specifically looking for H&A optical symmetry as many people may be satisfied with a superb light performer, though not H&A since H&A sometimes carries a premium with many vendors. Unless, this is what you mean by “bonus”.

 

[Karl_K]

Since lab symmetry has very little to do with light return I do not see how adding a bonus is warranted.
Since there is no way to verify h&a on a software level adding it is also a bad idea.
Adding a warning for good and under I could see.

 

[Garry H (Cut Nut)]

Since most reports do not grade for optical symmetry, just meet point symmetry, could the proposed version penalize potential unbranded H&A stones, especially since not all vendors provide H&A images for virtual inventory (hard enough to get IS and/or ASET). Im thinking the update may automatically make branded super-ideals far superior, while there may be comparable stones just as decent even amongst AGS Ideal and GIAXXX. Could this be an additional option for those who are specifically looking for H&A optical symmetry as many people may be satisfied with a superb light performer, though not H&A since H&A sometimes carries a premium with many vendors. Unless, this is what you mean by “bonus”.

Athena and Karl,
Meet point sym went out when labs realised they can grade symmetry more accurately and for less cost with the scan which all labs do (so they can identify if they have previously graded the same stone).
Scans are used and the settings for grades are up to each lab.
So while not perfect, the grade variations are reasnoable approximations for otpical given no photos.

if there are no H&A's photos then let the buyer beware. They can always see the arrows through a H&A scope even when set.

 

[Garry H (Cut Nut)]

There is another current thread running at https://www.pricescope.com/communit...ent-in-ideal-scope-image.246488/#post-4487984

And here is an example form a basic Helium scanner, which I believe is what GIA lab use for rounds:
https://www.octonus.com/oct/products/helium/polish/reports/Illustrated_report_for_brilliant.pdf

 

[Athena10X]

There is another current thread running at https://www.pricescope.com/communit...ent-in-ideal-scope-image.246488/#post-4487984

And here is an example form a basic Helium scanner, which I believe is what GIA lab use for rounds:
https://www.octonus.com/oct/products/helium/polish/reports/Illustrated_report_for_brilliant.pdf

Does GIA run the Helium scan on every RB for symmetry grading? If so, could the consumer ask the vendor to obtain the report by the GIA number and then plug specific numbers into the proposed HCA update?

 

[Athena10X]

Also, if polish can affect light performance, should anything less than very good polish be penalized, even if the diamond received an excellent cut grading?

 

[Garry H (Cut Nut)]

Does GIA run the Helium scan on every RB for symmetry grading? If so, could the consumer ask the vendor to obtain the report by the GIA number and then plug specific numbers into the proposed HCA update?

We wish

 

[Garry H (Cut Nut)]

Also, if polish can affect light performance, should anything less than very good polish be penalized, even if the diamond received an excellent cut grading?

If the sym or polish is less than VG (i.e good) GIA lower the cut grade

 

[Athena10X]

If the sym or polish is less than VG (i.e good) GIA lower the cut grade

To what extent could very good polish affect light performance of a diamond with an excellent cut grade compared to another practically identical diamond (per specs) with excellent polish? Would it be visibly noticeable?

 

[blueMA]

To what extent could very good polish affect light performance of a diamond with an excellent cut grade compared to another practically identical diamond (per specs) with excellent polish? Would it be visibly noticeable?

No, a "very good" polish won't affect the performance through the naked eye.
Read more https://yourdiamondteacher.com/diamond-grading/polish/

 

[Garry H (Cut Nut)]

Does anyone have an opinion about the topic?
Far too many segways

 

[Serg]

Athena and Karl,
Meet point sym went out when labs realised they can grade symmetry more accurately and for less cost with the scan which all labs do (so they can identify if they have previously graded the same stone).
Scans are used and the settings for grades are up to each lab.
So while not perfect, the grade variations are reasnoable approximations for otpical given no photos.

if there are no H&A's photos then let the buyer beware. They can always see the arrows through a H&A scope even when set.

Garry,
Labs have not scanners to grade Optical symmetry with best H&A accuracy.
Standard shadow scans can not separate just good H&A from best H&A.
Standard Table tilt accuracy for shadow scan is 0.1-0.2 degree and it does not depends only form scanner alignment. A dust on holder can easy tilt table on 0.1-0.2 degree.
0.2 table tilt is critical to grade symmetry in best H&A

 

[Garry H (Cut Nut)]

Garry,
Labs have not scanners to grade Optical symmetry with best H&A accuracy.
Standard shadow scans can not separate just good H&A from best H&A.
Standard Table tilt accuracy for shadow scan is 0.1-0.2 degree and it does not depends only form scanner alignment. A dust on holder can easy tilt table on 0.1-0.2 degree.
0.2 table tilt is critical to grade symmetry in best H&A

Sergey you miss-read my comments.
I said H&A's can only be judged by photos.
"let the buyer beware"

 

[gm89uk]

I would like opinions on adding a symmetry score to HCA.

Bonus for H&A X%, AGS Ideal Y%, Excellent Z%
No bonus for VG 0%
Penalty for Good, Fair and Poor

We are in Beta testing for an addition to HCA that indicates how big or small a round diamond looks like. Not just it's dimension relative to its carat weight, but an estimate taking into account peripheral light leakage. This will be called Holloway Cut Adviser Looks Like or HCA LL.
Part of the new data entry is symmetry. So it will be easy to add bonus and penalty to HCA (many people already seem to accept H&A's up to HCA 2.5).
Of course dimensions and carat weight are also part of the new data requirements.
As soon as practical we will also allow entry of any AGS or GIA report number - regulars already know that many report #'s already work this way.

Can anyone find an example of any EX or AGS0 for symmetry that you would consider not good enough for a Y% boost? With optical symmetry being so varied, I feel this tool will add an additional guess work to HCA (on top of theoretical averages etc). Symmetry doesn't always correlate to better light performance which is what I thought HCA was all about, rather than advantage tolk flavour diamonds H&A style stones.

I aay this as @Serg just shared this:
https://cutwise.com/compare/diamond-colorless?id[]=25549&id[]=26035
Which demonstrates the diamond with less symmetry was a great performer.

 

[Serg]

Sergey you miss-read my comments.
I said H&A's can only be judged by photos.
"let the buyer beware"

Sorry, Garry it not clear even after I reread all your comments twice.

Do you mean your comments: :"if there are no H&A's photos then let the buyer beware. They can always see the arrows through a H&A scope even when set."

Where did you say "H&A's can only be judged by photos"?
how has a client have to decide which a diamond is a H&A?( when can he use 3D model and when has he have to use H&A Photos?)
How will client receive 3D model from Labs?( Labs Reports have not information to grade optical symmetry)

I did not not understand How you want to do it. Your goal is clear for me but your implementation is very confusing for me.

 

[OoohShiny]

Does anyone have an opinion about the topic?
Far too many segways

I'm guessing you meant segues lol

[/pedant]


I think for me, I'm not sure how much added improvement in light performance an improvement in symmetry would/could/does produce, therefore what added benefit it would bring to the HCA(LL) tool - as a purchaser of a CBI I know the benefits of excellent light performance derived from attention to facets and symmetry, but can it be quantified/allocated a score?

 

[blueMA]

I'd rather see minor facets, esp lgh, get considered before symmetry.

 

[sledge]

I aay this as @Serg just shared this:
https://cutwise.com/compare/diamond-colorless?id[]=25549&id[]=26035
Which demonstrates the diamond with less symmetry was a great performer.

Maybe @Serg modified his original post, but I don't see where this link was shared above in his comments. Did it come from this topic, or elsewhere?

Quickly glancing over it, I'm not convinced optical symmetry was the only factor at play in that analysis. Yes, a stone with less optical symmetry did better than one with far better optical symmetry. However, look at the proportions:

Scan Bhajan (w/ less optical symmetry) = 59.69 table, 61.41 depth, 34.8 crown & 41.1 pavilion & 6.10 symmetry (assuming 10 is max)
GIA Bhajan (w/ less optical symmetry) = 59.7 table, 62 depth, 35 crown, 41.2 pavilion & excellent symmetry

Scan KP (w/ better symmetry) = 54.5 table, 62.9 depth, 35.5 crown, 40.65 pavilion & 7.26 symmetry
GIA KP (w/ better symmetry) = 55 table, 62.9 depth, 35.5 crown, 40.6 pavilion & excellent symmetry

In the case of @Garry H (Cut Nut)'s original thread, neither stone would receive an advantage or disadvantage as both are marked excellent by GIA. Granted, the scan data shows the KP stone to have better symmetry than the Bhajan stone, but again, it would have no bearing on his proposed calculation adjustments as the scanned data would not be available (and consequently, not used).

Ignoring that fact, look at the depth of the KP stone. I'm willing to bet that 62.9 depth played into the equation in a negative way.

I love this software analysis though. We are able to see the Bhajan stone enjoys about a 15% increase in fire and 5% increase in brilliance.

To better prove, or disprove, the effects that symmetry has on the stone I think you need a better set of test data that is more closely aligned proportionally.

Also, not sure how the scan accounts for the fluorescence (if at all) but the KP stone had very strong in an F color, whereas the D had none. Even by GIA literature, fluor typically isn't an issue but is more prone in stones with very strong.

Either way, very interesting link. Thank you for sharing.

 

[gm89uk]

Maybe @Serg modified his original post, but I don't see where this link was shared above in his comments. Did it come from this topic, or elsewhere?

Quickly glancing over it, I'm not convinced optical symmetry was the only factor at play in that analysis. Yes, a stone with less optical symmetry did better than one with far better optical symmetry. However, look at the proportions:

Scan Bhajan (w/ less optical symmetry) = 59.69 table, 61.41 depth, 34.8 crown & 41.1 pavilion & 6.10 symmetry (assuming 10 is max)
GIA Bhajan (w/ less optical symmetry) = 59.7 table, 62 depth, 35 crown, 41.2 pavilion & excellent symmetry

Scan KP (w/ better symmetry) = 54.5 table, 62.9 depth, 35.5 crown, 40.65 pavilion & 7.26 symmetry
GIA KP (w/ better symmetry) = 55 table, 62.9 depth, 35.5 crown, 40.6 pavilion & excellent symmetry

In the case of @Garry H (Cut Nut)'s original thread, neither stone would receive an advantage or disadvantage as both are marked excellent by GIA. Granted, the scan data shows the KP stone to have better symmetry than the Bhajan stone, but again, it would have no bearing on his proposed calculation adjustments as the scanned data would not be available (and consequently, not used).

Ignoring that fact, look at the depth of the KP stone. I'm willing to bet that 62.9 depth played into the equation in a negative way.

I love this software analysis though. We are able to see the Bhajan stone enjoys about a 15% increase in fire and 5% increase in brilliance.

To better prove, or disprove, the effects that symmetry has on the stone I think you need a better set of test data that is more closely aligned proportionally.

Also, not sure how the scan accounts for the fluorescence (if at all) but the KP stone had very strong in an F color, whereas the D had none. Even by GIA literature, fluor typically isn't an issue but is more prone in stones with very strong.

Either way, very interesting link. Thank you for sharing.

Hi Sledge, it was from a different topic:
https://www.pricescope.com/communit...uth-misalignment-in-ideal-scope-image.246488/

Bhajan actually has a T61.4%, D59.7% which makes it even more interesting.

Both got GIA Ex which would presumably bump their HCA score by z% as per Garry's post. They have fairly different symmetry but would get the same generic bump in score, and the lesser symmetry got more points.

So my point is, is adding vague scores in HCA for symmetry going to help improve info back to user about light performance?

 

[sledge]

Hi Sledge, it was from a different topic:
https://www.pricescope.com/communit...uth-misalignment-in-ideal-scope-image.246488/

Bhajan actually has a T61.4%, D59.7% which makes it even more interesting.

Both got GIA Ex which would presumably bump their HCA score by z% as per Garry's post. They have fairly different symmetry but would get the same generic bump in score, and the lesser symmetry got more points.

So my point is, is adding vague scores in HCA for symmetry going to help improve info back to user about light performance?

Eek, I did inverse the table and depth. Sorry about that! And yes, the case becomes even more crazy.

For fun & giggles:

• Bhajan Actual = 3.8 HCA
• Bhajan GIA = 3.5 HCA
• KP Actual = 2.0 HCA (rounded pavilion from 40.65 to 40.7, as HCA only supports tenths)
• KP GIA = 1.4 HCA

Without the HCA scores, I doubt if too many people would disagree the Bhajan stone isn't something that we would recommend. Yet that test shows it has better performance.

Reminds me of this...

 

[blueMA]

Reminds me of this...

That's hysterical! Though my eyes love the Bhajan stone - it's an extreme example but the look is similar to higher pavilion stones I love around 34/41.

 

[Serg]

Eek, I did inverse the table and depth. Sorry about that! And yes, the case becomes even more crazy.

For fun & giggles:

• Bhajan Actual = 3.8 HCA
• Bhajan GIA = 3.5 HCA
• KP Actual = 2.0 HCA (rounded pavilion from 40.65 to 40.7, as HCA only supports tenths)
• KP GIA = 1.4 HCA

Without the HCA scores, I doubt if too many people would disagree the Bhajan stone isn't something that we would recommend. Yet that test shows it has better performance.

@sledge
I did random screenshots.
Which does diamond look more bright for you? Right or left?

 

[sledge]

That's hysterical! Though my eyes love the Bhajan stone - it's an extreme example but the look is similar to higher pavilion stones I love around 34/41.

Haha, yeah that farm truck is lethal. The driver, FarmTruck, and his trusty side kick, AZN (Asian), are rather comical to watch. Both are a part of Street Outlaws OKC and they air on the Discovery channel. That truck is the real deal. If you ever see something roll up with one tire about half the width of the bed and shooting NOS out of the hood, prepare for a butt whippin'.

http://www.discovery.com/tv-shows/street-outlaws/bios/farmtruck/
http://www.discovery.com/tv-shows/street-outlaws/bios/azn/

By the way, when I saw those proportions of nearly 35/41, you immediately came to mind as we just had that conversation a week or so ago.

 

[sledge]

@sledge
I did random screenshots.
Which does diamond look more bright for you? Right or left?

No doubt, the Bhajan stone.

What I meant by my earlier comments is based on an HCA score and proportions, most people here wouldn't have ever picked that stone over one like the KP.

We would have been wrong, as your comparison shows.

 

[blueMA]

This is also interesting when zoomed waaaay down.

 

[gm89uk]

Nice video @sledge !

In all fairness, the Bhajan stone looks brighter because the arrows are lighting up, and not obstructed. My wife's diamond is a 35/40.8, and at my normal viewing distance (just less than 12 inches), I see just the occasional black arrow, rather than 8 stark black arrows. The 40.7- 40.8 pavilion superideals do not look like 8 black arrows in real life either. So is the assessment of the diamonds too close? More so than would be when someone is viewing the stone? Maybe the parameters and apparent brightness would be different if they were recorded and assessed at a different focal length.

I like the point at which the black arrow turns white, and dispersion is at its best.

I can of course view it closer and see the obstruction, but it's not a common way to view the diamond

@Serg in several of your photos KP has the LGF and the pavilion mains are obstructed. This suggests the video was taken at the distance most likely to pronounce the performance of the 34.8/41.2. Those two diamonds would excel at different distances and so it's not entirely fair to judge a winner at just one distance / level of obstruction.

Edit: That website is really interesting. You can rank by cut, fire and brightness and other attributes. Some of the stones there are quite surprising.
Like this one: which looks like an amazing stone, but is graded very good cut.
https://cutwise.com/diamond/32408?sp=43

 

[blueMA]

Here are 40.7 and 40.8 superideals for another vantage point. Many love the contrast, but I tend to notice the obstructions when the mains are not lit, depending on lighting as in the video.

https://www.pricescope.com/community/threads/cbi-vs-aca-another-pic-and-vid-comparison.236493/

 

[Serg]

Nice video @sledge !


I can of course view it closer and see the obstruction, but it's not a common way to view the diamond

@Serg in several of your photos KP has the LGF and the pavilion mains are obstructed. This suggests the video was taken at the distance most likely to pronounce the performance of the 34.8/41.2. Those two diamonds would excel at different distances and so it's not entirely fair to judge a winner at just one distance / level of obstruction.

Edit: That website is really interesting. You can rank by cut, fire and brightness and other attributes. Some of the stones there are quite surprising.
Like this one: which looks like an amazing stone, but is graded very good cut.
https://cutwise.com/diamond/32408?sp=43

What is your opinion about common way to see round diamonds in engagement rings ?
AGS defines distance view as 250mm and head obscuration 30 degree.
I believe it is too short distance and we use 350mm, that create 24 degree head obscuration for Ladies without wealth of hair on the head sides( otherwise head obscuration could much bigger)


it is very tricky to model correctly human stereo vision by mono camera.
To verify Dibox2.0 head obscuration angle we compared Dibox2,0 stereo movies on stereo TV with observation of real diamonds.
We found that 30 degree creates too strong obscuration , 20-22 degree is not big enough to create good brilliancy for typical ASG0 RBC. Finally we selected 26 degree, but may be 24 degree is better.
Absolutely correct results possible only with stereo camera but it is much more complicated and expensive setup .

What is your definition for common head obscuration ?

about 5.30ct Ankit diamond : which looks like an amazing stone, but is graded very good cut.

It is my headache last weeks. The brilliancy score 0.88 ( VG) is also surprise for me. I did not find a reason of such low score yet. This movie had been done from Dibox2.0-18x15 recently assembled for big diamonds.( 5ct is too big for standard Dibox2.0). May be something wrong with head obscuration but I did not find exact reason yet.
In same time I found that Crown halves are dark to often .

check I3D report https://cutwise.com/report/?dataPat...84/source.src/Ankit_1196930303-report.js.json

Crown azimuth deviation from Ideal. Halves have painting 2 degree.

Btw. GIA grade is EX, and our cut grade is also EX. I have not any idea why an operator uploaded LAB cut grade VG, I have asked to check a reason and fix it.( most probably human mistake)

 

[EvaEvans]

@Garry H (Cut Nut)
I applause your idea to add the symmetry as a factor for the HCA!
I would buy a diamond with not excellent lab cut grade or HCA score above 2.0, but only if the symmetry is excellent.
I pay much more attention to the symmetry than to the common standards of excellent/ideal cut.
The importance of the symmetry for me is essential.