Diamond Light Performance

[retailresale101]

Hello - I am a little confused by all the guidance around light performance. I have a GIA triple excellent stone that (1) does not hit all the light performance specs found on the Beyondthe4Cs website (crown angle is slightly off), but (2) does otherwise qualify as ideal pursuant to the below linked AGS screener.

I then typed the specs of the stone into the HCA cut advisor and it reads 2.5 (and I understand below 2 is worth considering).

How should I interpret all of this information? Should I reject the stone since it scored above 2 on HCA or consider it since it falls within the AGS guidelines?

Btw these are for studs. It’s been very challenging to find a pair of studs that hit everything. The current pair I am considering has one stone with an HCA score below 1 and another that is above 2. Both triple excellent and crown angles that are slightly off from the Beyond 4Cs guidance but otherwise ideal under AGS.

Beyond 4 Cs guidance:

What Are the Ideal Proportions For Round Cut Diamonds? (Revealed!)

We reveal the ideal proportions you should look out for in round cut diamonds that will give the best sparkle and brilliance for your engagement ring.

beyond4cs.com

AGS screener:

https://www.diamondscreener.com/wp-content/uploads/reference/agsl_proportion_charts.pdf

Would appreciate the group’s thoughts and wisdom!

 

[lovedogs]

What are the specs of your stones and do you have pics?

 

[retailresale101]

Don’t have the pics and certs yet, but here are the stats - both G, VS1, triple excellent cut:

	Stone 1	Stone 2
Dimensions	6.98x7.02x4.37	6.97x7.01x4.28
Table	56	55
Depth	62.5	61.3
Crown	35.5	33.5
Pavillion	40.8	40.8
Lower girdles	80	80
Star facets	50	50
Girdle thickness	M-ST	M-ST

 

[Old_Fossil]

Hello @retailresale101 To get you started, I offer the following matched pairs that will have exemplary light performance. Based on your search criteria above, I think you will find these will be an excellent start point for your search.

Diamond pair details | Complete characteristics for chosen diamond pair

The most carefully chosen diamond pair. Every diamond is unique, but we choose the most similar diamond pair

www.whiteflash.com

1.311 J VS2 Signature Round

Buy diamonds online - AGS Graded 1.311 carat J VS2 super ideal cut Brian Gavin Hearts & Arrows Round Cut diamond. Lifetime Upgrade Policy!

www.briangavindiamonds.com

I recently went through this process and selected a pair of I color WF ACA studs and we couldn't be more pleased with their performance. I applaud your initial focus on cut, as that sets the light performance. I am of the school of thought that in studs of this size, you can go with I or J color when you have a super ideal cut as they will show quite white when worn on the ear.

All the best in your search. Please keep us posted and share your final decision - I am not one of the expert PSers here, but those that are experts are more than happy to help you get the best return on your investment.

 

[0515vision]

I love Paul Gian of Beyond4Cs. He helped me pick my 2.17 cushion which I adore.

You’re looking at different screening tools which have different levels of specificity. Triple Ex is a gross screening tool. “Ideal” is a term that is again based on gross measurements. There are gradations within the “ideal” label.

HCA is one step above using the angles. It’s more of a way to screen out stones rather than pick a singular diamond. Once you ask PS-ers, you’re taking into account the angles and the videos - that’s an even higher level of screening.

This is why the wise @lovedogs immediately asked for videos. All the angles can be right, but the combination sometimes doesn’t work. Also pavilion twist is only seen with the eye, never detected on a certificate. Not to mention tinges, paddling, painting & digging and the rest of the rascally bunch.

What’s your budget? Do you want us to faint a pair or simply match one of the stones you already mentioned? Offhand, that 33.5 CA feels shallow, but we’d want to see it.

The pairs posted by @Old_Fossil are gorgeous! Hope this helps!

 

[Garry H (Cut Nut)]

Stone 2 has better (shallower) earring proportions - but largr tables up to 59% work better for ER's

 

[V_sh]

Stone 2 has better (shallower) earring proportions - but largr tables up to 59% work better for ER's

Don’t have the pics and certs yet, but here are the stats - both G, VS1, triple excellent cut:

	Stone 1	Stone 2
Dimensions	6.98x7.02x4.37	6.97x7.01x4.28
Table	56	55
Depth	62.5	61.3
Crown	35.5	33.5
Pavillion	40.8	40.8
Lower girdles	80	80
Star facets	50	50
Girdle thickness	M-ST	M-ST

Hi,

I mainly assess diamonds regarding the angles of their main facets (Main crown, Main Pavillion, table) and the best combination of these three facets can be found in Hearts & Arrows proportion charts (in my opinion)

It matters how we look at a Round Brilliant diamond a well-balanced cut that shows Fire, Brilliance, and Scintillation almost equally or we are looking for one or two of these properties in a diamond cut

For a balanced cut, I prefer to compare the main facets (at first sight) with the Tolkowsky sweet line and H&A proportions

I do not agree with Garry and I think Stone 1 can be more balanced in terms of Fire, Brilliance, and Scintillation
But I think Garry prefers stone 2 based on his experience with earings; I'm sure that there are quite plenty of differences because a diamond on an earing is viewed vertically but a diamond on a ring is viewed horizontally (some light sources are less effective if we view it horizontally)

Garry, would you please enlighten us with your experiences?


You may like the following charts :

 

[0515vision]

@Garry H (Cut Nut) has a thread where he "experimented" with his wife's earrings. Here's my vague summation: He had one stud of "ideal" cut and another where the crown angle was shallow - 33.5, I think. Everyone (including diamond experts) kept choosing her shallower stud in all conditions - dirty, clean, different lighting. It looked whiter all the time.

It's possible to find the thread, but at the moment, I'm short on time.

 

[Dreamer_D]

You might have an easier time finding matches if you aren’t concerned about them being identical clarity and color.

 

[Kim N]

@Garry H (Cut Nut) has a thread where he "experimented" with his wife's earrings. Here's my vague summation: He had one stud of "ideal" cut and another where the crown angle was shallow - 33.5, I think. Everyone (including diamond experts) kept choosing her shallower stud in all conditions - dirty, clean, different lighting. It looked whiter all the time.

It's possible to find the thread, but at the moment, I'm short on time.

Here's the link.

Shallow crown and deep pavilion question

Hi PSers!=) I've learnt a lot through this wonderful forum during these couple of weeks. I'm still trying to understand relation between pavilion and crown angle in terms of optical performance, especially in the case of the lower crown angle and higher pavilion angle. I know about ideal...

www.pricescope.com

 

[Garry H (Cut Nut)]

Hi,

I mainly assess diamonds regarding the angles of their main facets (Main crown, Main Pavillion, table) and the best combination of these three facets can be found in Hearts & Arrows proportion charts (in my opinion)

It matters how we look at a Round Brilliant diamond a well-balanced cut that shows Fire, Brilliance, and Scintillation almost equally or we are looking for one or two of these properties in a diamond cut

For a balanced cut, I prefer to compare the main facets (at first sight) with the Tolkowsky sweet line and H&A proportions

I do not agree with Garry and I think Stone 1 can be more balanced in terms of Fire, Brilliance, and Scintillation
But I think Garry prefers stone 2 based on his experience with earings; I'm sure that there are quite plenty of differences because a diamond on an earing is viewed vertically but a diamond on a ring is viewed horizontally (some light sources are less effective if we view it horizontally)

Garry, would you please enlighten us with your experiences?


You may like the following charts :

Hi V sh,
I see you have attended a lot of OctoNus Lexus presentations
I think someone posted a link to my original post about the shallow earrings. Unless diamonds are very large, it is rare to see a flash of fire - so therefore its all about brilliance.
Here is an excerpt from my forthcoming book:

In 2005, I replaced one of my wife’s earring Ideal cut stones with a shallow
diamond. The shallow stone had a 59.5% table, 31.3° crown and 40.6°
pavilion with not very good symmetry. That equates to cut grades of GIA
Good or AGS 3 or 4. The remaining Ideal cut diamond had a 55.3% table,
34.9° crown and 40.75° pavilion with perfect optical symmetry (Hearts and
Arrows).
After 3 months of annoying many people by asking which looked better,
there was no doubt that the shallow stone performed better in all sorts of
lighting environments. Clean or dirty. I had my wife swap the diamond earrings
from ear to ear every day to ensure they were equally dirty.
That was when I discovered that shallow diamonds lose less brilliance when
dirty. Peter Yantzer (then Director of the AGS Lab) preferred the dirty shallow diamond earring, much to his surprise.
The ideal cut diamond is on the left (1.06ct H VS2) and the shallow stone on the right (1.03ct D SI2). (the images are the same as in the linked post) The diamonds are equally dirty in both photos. The top Ideal-Scope photo was taken in the hotel room that night we went out to dinner with Peter Yantzer in Las Vegas in 2005. The bottom photos show that the
ideal cut diamond (left) shows more dirt and is duller, especially around the crown facets.
The shallow diamond Ideal-Scope image on the right in the images above
has blotchy dark areas indicating the diamond is shallow and has poor symmetry.
People in the know would reject it. Yet this stone always outshone the
“ideal cut”, both clean and dirty, when people were observing the earrings
from a meter or more away.
When given both clean earrings to hold and examine close-up, most people
preferred the Ideal cut diamond. Most younger people, with their better
close-up eyesight, preferred the ideal cut.
You must clean your diamonds as often as practical. Earrings that are worn
all the time are out of sight (behind the hair) and should be cleaned at least
once a week.

 

[Garry H (Cut Nut)]

" the best combination of these three facets can be found in Hearts & Arrows proportion charts (in my opinion)" V sh it is possible to cut H&A's diamonds across a 10 degree range of crown angles (with compensating inverse pavilion angles on a rule of 5:1).

 

[V_sh]

Hi V sh,
I see you have attended a lot of OctoNus Lexus presentations
I think someone posted a link to my original post about the shallow earrings. Unless diamonds are very large, it is rare to see a flash of fire - so therefore its all about brilliance.
Here is an excerpt from my forthcoming book:

In 2005, I replaced one of my wife’s earring Ideal cut stones with a shallow
diamond. The shallow stone had a 59.5% table, 31.3° crown and 40.6°
pavilion with not very good symmetry. That equates to cut grades of GIA
Good or AGS 3 or 4. The remaining Ideal cut diamond had a 55.3% table,
34.9° crown and 40.75° pavilion with perfect optical symmetry (Hearts and
Arrows).
After 3 months of annoying many people by asking which looked better,
there was no doubt that the shallow stone performed better in all sorts of
lighting environments. Clean or dirty. I had my wife swap the diamond earrings
from ear to ear every day to ensure they were equally dirty.
That was when I discovered that shallow diamonds lose less brilliance when
dirty. Peter Yantzer (then Director of the AGS Lab) preferred the dirty shallow diamond earring, much to his surprise.
The ideal cut diamond is on the left (1.06ct H VS2) and the shallow stone on the right (1.03ct D SI2). (the images are the same as in the linked post) The diamonds are equally dirty in both photos. The top Ideal-Scope photo was taken in the hotel room that night we went out to dinner with Peter Yantzer in Las Vegas in 2005. The bottom photos show that the
ideal cut diamond (left) shows more dirt and is duller, especially around the crown facets.
The shallow diamond Ideal-Scope image on the right in the images above
has blotchy dark areas indicating the diamond is shallow and has poor symmetry.
People in the know would reject it. Yet this stone always outshone the
“ideal cut”, both clean and dirty, when people were observing the earrings
from a meter or more away.
When given both clean earrings to hold and examine close-up, most people
preferred the Ideal cut diamond. Most younger people, with their better
close-up eyesight, preferred the ideal cut.
You must clean your diamonds as often as practical. Earrings that are worn
all the time are out of sight (behind the hair) and should be cleaned at least
once a week.

Hi Garry,
Thanks for your valuable explanation and time, that means a lot.

I like and practice any worthy explanation or data by companies or people, and may accept them after assessing and experimenting with them; so Octonus, Janak, and many other friends and masters like you, I followed and have been learning from.

Yeah, that was easy to guess that you have a valuable experience behind your choice, although I didn't see that original thread, but I found some other data you provided; Thanks for sharing.
The importance and impact of cleaning was dramatic.

One question remains for me, did you compare diamonds when they were on ears (vertically), or did you assess them by looking at them from top to bottom (horizontally)?

Do you also think "good diamond design" is based on how one wants to view his/her diamond or how/where the diamond gonna be worn?


Bests,

 

[Garry H (Cut Nut)]

The importance and impact of cleaning was dramatic.
One question remains for me, did you compare diamonds when they were on ears (vertically), or did you assess them by looking at them from top to bottom (horizontally)?
Do you also think "good diamond design" is based on how one wants to view his/her diamond or how/where the diamond gonna be worn?


Bests,

Both, in the hand people preferred the ideal Tolkowsky cut, especially younger people and short sighted people.
In the ears I do not remember a single person preferring the ideal cut. Clean or dirty.
Also the proportions This shallow girl gif explains why shallow stones go dark!
And the proportions that look best in earrings are on the left of this chart - because fire is rarely seen in that orientation.

 

[V_sh]

Both, in the hand people preferred the ideal Tolkowsky cut, especially younger people and short sighted people.
In the ears I do not remember a single person preferring the ideal cut. Clean or dirty.
Also the proportions This shallow girl gif explains why shallow stones go dark!
And the proportions that look best in earrings are on the left of this chart - because fire is rarely seen in that orientation.

Thank you so much Garry for such an informative and precious explanation, that's a great help.

For sure I'll do experiments and calculations to understand these better.

Sincerely,

 

[Garry H (Cut Nut)]

Thank you so much Garry for such an informative and precious explanation, that's a great help.

For sure I'll do experiments and calculations to understand these better.

Sincerely,

please report back

 

[retailresale101]

These responses are so helpful and insightful, thank you so much!!