ASETs and fancy cuts

[Serg]

Hi All,

I was looking forward to this thread as I was looking at radiant, asscher and cushion cut diamonds for a possible purchase. I am not one of the knowledgeable consumers who frequent this board. I was hoping to see asets for those makes. So here is my question.

I have noticed in these cuts, the center of the aset is red, but is ringed by the white color, to form a square(ish) surround. The the color moves to red, green, blue and possibly more white. Is this ring around the red center, light leakage, and does it denote something a diamond buyer would best avoid?

David, you usually divert the conversation to what suits you. . I want to use the aset as a selection tool, along with seeing the diamond, after checking the aset, but consumers need to read them properly, so please let the others continue to show us asets. (or start.)

Thanks,

Annette

Perhaps you mean the zone around this central region that has considerable leakage?
This is not desirable in a colourless diamond smitcompton. in a fancy pale diamond it can be good if more of the stone is green, with little or mo red or blue.

Garry, the actual Diamond in the picture you posted is on a black background.
We notice that "ring" area is not actually all leakage, I even think most of that area is lit up by light entering just below 45 degrees, an area AGSL doesnt take into consideration when grading for LP (thats without taking tilt into consideration on this specific example you posted).
In my opinion, this area could be designed in such way it becomes a positive visual thus minimizing the deduction for leakage.

You're take?

Its pretty much a black hole Yoram

Garry,
please publish images for left and right eyes under same light

 

[diagem]

Garry, the actual Diamond in the picture you posted is on a black background.
We notice that "ring" area is not actually all leakage, I even think most of that area is lit up by light entering just below 45 degrees, an area AGSL doesnt take into consideration when grading for LP (thats without taking tilt into consideration on this specific example you posted).

Hi Diagem,

I am not Garry but I can hopefully help this question which I believe is about AGS-PGS cut grading. (Not just a plain ASET 30 image which we are discussing here).

I believe the border areas Red/Green (43 - 44 - 44.9) are treated differently by AGSL cut grading for LP, its a scaled penalty and closer to 45 the lesser the deduction. But if those Green regions are mostly white with a hint of Green than its mostly leakage like in Garry's example and should be more heavily penalized.

Over the years AGSL has started to allow diamonds with larger culets to still get AGSL 0 (like your example), I beleive they encourage new designs and set tolerances on a case by case basis which allow things like more blue in a princess cut, 20% green in a fancy etc.

Hello MD,

Yes, I know how the AGSL deduction system works, but my question is what if that region is not green nor white? instead its build from light coming in at right below 45 deg. and is shown as scattered and symmetric low light return areas. But definitely not leakage..., see Aset:




How would you or Garry et-al characterize this?

BTW, I am a bit responsible for the AGSL allowance to change their culet policies on their LP grading.

 

[smitcompton]

Hi Garry,

The example aset you posted is exactly what I'm talking about. Thanks for answering. There were quite a few with that ring around the red.

Thanks,

Annette

Hi Yoram.

Have you done anything with your emeralds?

 

[MelisendeDiamonds]

How would you or Garry et-al characterize this?

BTW, I am a bit responsible for the AGSL allowance to change their culet policies on their LP grading.

What area of the crown are you referring to?, I assume it is the corners of the table?
Good job on getting the AGS society to change the notion that a stone with a bigger culet can't still have ideal brilliance.

 

[Rockdiamond]

This thread is EXTREMELY informative to me, especially because I adore fancy cut diamonds over any shape, so thank you!

Question: With all of the marquise threads popping up lately (yay...Lol!) what do you all recommend when looking at an ASET of a fancy cut? Assuming that the buyer has seen the original diamonds in person, but they just can't decide...or if seeing them in person is not an option, what is it that the buyer should look for when viewing an ASET of a fancy cut? (I know about the bowties, but feel free to mention it again for those that may not be aware of them.) Also, if ASETs really don't add any valuable info to fancies, feel free to share that as well.

Jazz and Chocolate.....Noiyce!!!

One thing I notice, as a diamond buyer, is that there's bow ties that I view as detrimental- because they stay dark thorough a range of tilt. Not pretty to me.
A really nicely cut Marquise Brilliant will have a lot of contrast- that may look like a bow tie in a static pose- yet as soon as the diamond is put into motion, the dark areas flash on an off in a pleasing manner.
So that's a "bow tie" that many people will love.

There's also Marquise Modified Brilliant stones with additional facets on the bottom which alleviate the larger areas of contrast ( bow tie)

As I'm not a cutter, I don't find it necessary to get into all the technical details of why one is better, because my job is to select, as opposed to fix it.
Participating here has given me a lot of insight to the why's - but I still rely on my eyes.

An issue that affects selection and this whole discussion is contrast and brightness.
As Garry mentioned, when you reduce contrast, brightness ( as defined by the terms we're using here) is less.

The terms, in my opinion are designed to favor brightness, over scintillation.
Basically, part of the crux of the discussion- which is preferable- a lot more, less bright sparkles as compared to larger, brighter and fewer reflections.

As far as the underlined part- If one took the times to look at many stones, and correlate them to their ASET conclusions can be drawn.
Is it necessary to use ASET to successfully buy well cut Fancy Shape diamonds?
No, it's not.
The problem that occurs is when people are led to believe ASET is some sort of conclusive test.
Which leads to questions like:
"Which of these ASET's is better?"
In a large percentage of cases people are asking what's better chocolate or vanilla, yet they think they're asking an objective question.

AGSL has been referred to here- and they have an agenda in promoting what they term "Light Performance"- which has absolutely ZERO to do with beauty, or even how well a given diamond is cut.

 

[diagem]

How would you or Garry et-al characterize this?

BTW, I am a bit responsible for the AGSL allowance to change their culet policies on their LP grading.

What area of the crown are you referring to?, I assume it is the corners of the table?
Good job on getting the AGS society to change the notion that a stone with a bigger culet can't still have ideal brilliance.

Not the crown but yes the four corners of the table, what would you call these areas?
The culet issue was elementary, and the AGSL committee in charge also agreed
99% of my works are signed off with an open culet. It definitely adds character and then some...

 

[MelisendeDiamonds]

How would you or Garry et-al characterize this?

BTW, I am a bit responsible for the AGSL allowance to change their culet policies on their LP grading.

Not the crown but yes the four corners of the table, what would you call these areas?

Well like you I have an issue with the ASET model in DC and grey areas where it should be white and maybe a little green, and maybe Serg knows how to fix the lighting. Those grey areas are an artifact of the DC lighting and shouldn't appear on a photographed backlit ASET.

Perhaps you could post a photograph of the ASET of that stone or a similar one.

 

[MelisendeDiamonds]

AGSL has been referred to here- and they have an agenda in promoting what they term "Light Performance"- which has absolutely ZERO to do with beauty, or even how well a given diamond is cut.

Who is posting for AGSL here and what exactly is this agenda they supposedly have?

 

[Rockdiamond]

Garry, the actual Diamond in the picture you posted is on a black background.
We notice that "ring" area is not actually all leakage, I even think most of that area is lit up by light entering just below 45 degrees, an area AGSL doesnt take into consideration when grading for LP (thats without taking tilt into consideration on this specific example you posted).

Hi Diagem,

I am not Garry but I can hopefully help this question which I believe is about AGS-PGS cut grading. (Not just a plain ASET 30 image which we are discussing here).

I believe the border areas Red/Green (43 - 44 - 44.9) are treated differently by AGSL cut grading for LP, its a scaled penalty and closer to 45 the lesser the deduction. But if those Green regions are mostly white with a hint of Green than its mostly leakage like in Garry's example and should be more heavily penalized.

Over the years AGSL has started to allow diamonds with larger culets to still get AGSL 0 (like your example), I beleive they encourage new designs and set tolerances on a case by case basis which allow things like more blue in a princess cut, 20% green in a fancy etc.

I never implied anyone was posting for AGSL - rather that AGSL was referred to.
Right now Light Performance is seriously biased toward contrast and brilliance- as opposed to scintillation.

 

[Rockdiamond]

I'd like to clarify my point- after considering it further- and speaking to colleagues.

The current state of AGSL cut grading is wrapped up heavily in the internet at this point. Even in the smaller market share of AGSL, cut grading for fancies, in particular, is pretty much an internet product.
Pretty much any shopper that is familiar with AGSL is also familiar with GIA.
GIA has such a heavy advantage that it's simply not feasible to send Fancy Shaped diamonds to AGSL, unless there's a specific light performance goal, such as the branded antique style cushion, for example.
In that, AGSL does a great job of getting cutters to meet exacting standards. It's very cool.
I don't think the AGSL Princes cut grade is nearly as relevant today as the cut grades on stones like the Octavia.

Current state of affairs is that no cutter, or dealer has ( I believe) ever tried to work with AGLS in developing a cut grade system that could help consumers quantify a good "Crushed Ice" type of diamond.
It's no "conspiracy" as much as no one has properly advocated the types of stones that show a lot of green in aset.

One potential solution to allow AGSL to gain market share- which may or may not have been suggested to AGSL- is to issue a product that's only a cut grade- allowing dealers to use GIA color clarity grading, and AGSL cut grading.

 

[Garry H (Cut Nut)]

AGSL has been referred to here- and they have an agenda in promoting what they term "Light Performance"- which has absolutely ZERO to do with beauty, or even how well a given diamond is cut.

Who is posting for AGSL here and what exactly is this agenda they supposedly have?

David do you have the right to say that AGSL have no right to promote their agenda of light performance?
That reference to AGSL is bad or not allowed in these discussions?
That LP or AGSL interpretation of LP has ZERO to do with beauty?

I also can not comprehend a discussion about diamond beauty or how well cut a diamond is should not include all the aspects such as brightness, briliance, contrast, sparkle, scintillation and fire and any other terms you or anyone else wants to use.
In his discussion based on "ASET and fancy cuts" fire is possibly the least relevant, but even in the case of fire, an ASET scope can show if a diamond's virtual facets are going to be too small for that diamond to show visible fire. Crushed ice stones need to be huge before they can show fire would you agree about that at the very least?

Back to topic - so far I have not heard anyone mention that you can buy a diamond based on an ASET image alone? Have you?

I do believe that ASET is the most useful readily available tool for consumers here on Pricescope to reject fancy cut diamonds.
Just like HCA, it is a method to reduce the avaliable diamonds to a smaller number that have a better chance to be beautiful. The selection process after that is another topic, and we could diiscuss that too, but maybe on a different new thread?

 

[MelisendeDiamonds]

Right now Light Performance is seriously biased toward contrast and brilliance- as opposed to scintillation.

Scintillation can either be increased or decreased at the expense of virtual facet (or flash size) it is not directly correlated with brilliance.
Whether one prefers faster smaller flashes or slower bigger ones is a matter of taste. When flashes are too small they are not noticeable to the eye so having faster scintillation will only be helpful up to a point.

You can have both fast scintillation and edge to edge brilliance but you are going to give up some spread and yield, the Adura Cut Cornered Square I posted above and some 4 Chevron Princess cuts are two examples of this.

 

[Rockdiamond]

Garry- please read my second post about this.
AGSL has every right to promote the work they do.
I'd love to see AGSL gain more prominence- having to wait 2 months for a GIA report will do that to you.

I'm not saying ASET has no value- clearly it does.
I do feel that as a tool of rejection, application may be problematic.
Why should I reject a stone because you don't love it?
It's not about the device, it's about how to use it.
To be of value, the user must know what sort of aset they are looking for, as it relates to the stone they want.
If they're led to believe 20% is the max amount of green they should look for, that's a problem if they want a nicely performing crushed ice style diamond.
if they're led to believe that white areas, representing "leakage" are bad in and of themselves, they are also going to be disappointing if they want a nicely cut "crushed ice" type of diamond.


About fire- I have to thank you for pointing it out Garry.
For the last few weeks I've been noting the presence of fire in my photos.
The stone below is smaller than 1ct.


We are really in agreement Garry- I really have learned a ton during the process of going back and forth over the years- and I think you for that.
It's a balance of your terms, "brightness, brilliance, contrast, sparkle, scintillation and fire"- as well as spread and shape. The last two elements need more weight in the equation to a lot of buyers.

I also believe that if and when AGSL broadens the concept of "light performance" you will no doubt be at the forefront in developing ways to analyze the stones.

 

[Garry H (Cut Nut)]

Thanks David

To be of value, the user must know what sort of aset they are looking for, as it relates to the stone they want.
If they're led to believe 20% is the max amount of green they should look for, that's a problem if they want a nicely performing crushed ice style diamond.
if they're led to believe that white areas, representing "leakage" are bad in and of themselves, they are also going to be disappointing if they want a nicely cut "crushed ice" type of diamond.

I think it may have been me who helped you learn that an even green color with fine disseminated white leakage makes the very best crushed ice diamonds. And these are also the criteria for the best looking colored diamond cuts (where the initial material is on the paler side).
You will never ever have found me telling consumers who want crushed ice look to avoid it.
But they will never have as much fire as the type of cuts and virtual facets that Melisende is describing. Not unless they are like 10ct. And wow! at that size and above crushed ice can be stunning.

BTW see page 48 of the August Rapaport magazine. It just arrived and they layed it out very well.

 

[Rockdiamond]

Amazing Garry- congratulations!
For those who don't have access to the magazine- it's an article about remarkable new technology to photograph diamonds in which Garry participated in developing.
The article touches upon some of the things we're discussing here. Scintillation, brilliance, fire, stereoscopic vision, and the effect on these things.
Kudos Dude.

 

[Rockdiamond]

Thanks David

To be of value, the user must know what sort of aset they are looking for, as it relates to the stone they want.
If they're led to believe 20% is the max amount of green they should look for, that's a problem if they want a nicely performing crushed ice style diamond.
if they're led to believe that white areas, representing "leakage" are bad in and of themselves, they are also going to be disappointing if they want a nicely cut "crushed ice" type of diamond.

I think it may have been me who helped you learn that an even green color with fine disseminated white leakage makes the very best crushed ice diamonds. And these are also the criteria for the best looking colored diamond cuts (where the initial material is on the paler side).
You will never ever have found me telling consumers who want crushed ice look to avoid it.
But they will never have as much fire as the type of cuts and virtual facets that Melisende is describing. Not unless they are like 10ct. And wow! at that size and above crushed ice can be stunning.

BTW see page 48 of the August Rapaport magazine. It just arrived and they layed it out very well.

Although I heave learned a lot from you Garry- it was Stan who taught me about ASET and green in Radiant Cuts, long ago.

Part of why we will always have slightly different take on things is the italicized part.
Yes, we give up fire in spreadier stones crushed ice stones under 10ct, but to some people the "but" is they have to accept a smaller diamond for the money to get fire.
And come on, I'm sure you've seen some stunning small crushed ice fancy colors.
On stones below 1/2, getting a nice even color, and sparkle in itself is an accomplishment. But they are out there.

 

[Garry H (Cut Nut)]

David I have never ever argued against crushed ice for fancy colored diamonds. Never ever, like forever.

Yoram can attest to that

 

[Rockdiamond]

I'm sure that's correct...
What about in colorless diamonds?
I've also seen some remarkably even, bright, colorless crushed ice, in cushion, radiant, and even modified Pear Brilliant diamonds.
Not a lot of fire, I agree. But some.
And many other positive attributes in other ways, such as shape, and potential spread.

 

[Garry H (Cut Nut)]

Hi All,

I was looking forward to this thread as I was looking at radiant, asscher and cushion cut diamonds for a possible purchase. I am not one of the knowledgeable consumers who frequent this board. I was hoping to see asets for those makes. So here is my question.

I have noticed in these cuts, the center of the aset is red, but is ringed by the white color, to form a square(ish) surround. The the color moves to red, green, blue and possibly more white. Is this ring around the red center, light leakage, and does it denote something a diamond buyer would best avoid?

David, you usually divert the conversation to what suits you. . I want to use the aset as a selection tool, along with seeing the diamond, after checking the aset, but consumers need to read them properly, so please let the others continue to show us asets. (or start.)

Thanks,

Annette

Perhaps you mean the zone around this central region that has considerable leakage?
This is not desirable in a colourless diamond smitcompton. in a fancy pale diamond it can be good if more of the stone is green, with little or mo red or blue.

Garry, the actual Diamond in the picture you posted is on a black background.
We notice that "ring" area is not actually all leakage, I even think most of that area is lit up by light entering just below 45 degrees, an area AGSL doesnt take into consideration when grading for LP (thats without taking tilt into consideration on this specific example you posted).
In my opinion, this area could be designed in such way it becomes a positive visual thus minimizing the deduction for leakage.

You're take?

Its pretty much a black hole Yoram

Garry,
please publish images for left and right eyes under same light

I had to find the stone again.
Same set up, plus ASET, 8 degrees each side = about 10-12 inches 25cm-30cm viewing distance.
I left dispersion on for David
I think when the stone is tilted there is some dome reflection - Sergey can it be turned off?
Also I am not sure what pattern and intensity calc settings to use (20,10).

 

[Garry H (Cut Nut)]

I'm sure that's correct...
What about in colorless diamonds?
I've also seen some remarkably even, bright, colorless crushed ice, in cushion, radiant, and even modified Pear Brilliant diamonds.
Not a lot of fire, I agree. But some.
And many other positive attributes in other ways, such as shape, and potential spread.

David I selected Cushion CO in our Master Stone Set http://www.octonus.com/oct/mss/diamC0.html.
it was the best example I found on a buying trip several years ago.
Our aim is for all the MSS stones have 3/4ct 5.8mm round diamond spread. This stone weighs 0.78ct.

While it has a little bowtie effect, overall its a good e.g. of crushed ice. Its nice, but i prefer the fire and brilliance of the cushion cuts that Sergey and Yuri have designed, and love the scintillation of some of them.
So far there are only MSS samples up to Cushion 6 shown there, but Cushion 10 has been polished.
I have 19 of the earlier stones and need to work out what I am going to do with them.

 

[Garry H (Cut Nut)]

The article I have mentioned a few times is now available on RapNet.com
http://www.rapnet.com/News/NewsItem...IssueID=0&ArticleTitle=Vision+Impacts+Sparkle
I will also post it in topic of its own.
But it is relevant to the post 2 up from this where I have done as Sergey suggested - to show what each eye might see.

 

[diagem]

How would you or Garry et-al characterize this?

BTW, I am a bit responsible for the AGSL allowance to change their culet policies on their LP grading.

Not the crown but yes the four corners of the table, what would you call these areas?

Well like you I have an issue with the ASET model in DC and grey areas where it should be white and maybe a little green, and maybe Serg knows how to fix the lighting. Those grey areas are an artifact of the DC lighting and shouldn't appear on a photographed backlit ASET.

Perhaps you could post a photograph of the ASET of that stone or a similar one.

Dont have a real Aset of this stone handy but do have this interesting image: same Diamond, same lighting environment and same camera position.
-left image, bottom lit strong white light.
-right image diamond on solid background.
can you see the interesting difference?

but..., the real Aset image should be almost identical to the DC one I posted above...

 

[MelisendeDiamonds]

Dont have a real Aset of this stone handy but do have this interesting image: same Diamond, same lighting environment and same camera position.
-left image, bottom lit strong white light.
-right image diamond on solid background.
can you see the interesting difference?

Diagem,



I don't really understand the lighting in those photographs. The culet(leakage) is dark in the black background image but the corners of the table (outlined in red) that I would also expect to also be darker than the white background one are not. Further it seems like both black and white images are being backlit because I see physical facets not virtual facets and thus the pictures have no direct correlation to ASET.

but..., the real Aset image should be almost identical to the DC one I posted above...

The crucial area to look at as you pointed out is on the corners of the table, there should not be so much grey in the photographed ASET image allowing for better resolution of colors in that region.

 

[Serg]

but..., the real Aset image should be almost identical to the DC one I posted above...

The crucial area to look at as you pointed out is on the corners of the table, there should not be so much grey in the photographed ASET image allowing for better resolution of colors in that region.

The crucial area to look at as you pointed out is on the corners of the table, there should not be so much grey in the photographed ASET image

Partial leakage gives grey zones or pale zones ASET. Why do you think that the diamond has not partial zones?

 

[RADIANTMAN]

I think this comment from Garry bears repeating;

"While it has a little bowtie effect, overall its a good e.g. of crushed ice. Its nice, but i prefer the fire and brilliance of the cushion cuts that Sergey and Yuri have designed, and love the scintillation of some of them."

Garry is expressing his personal preference not scientifically verifiable superiority of one style over the other. I think the heart of the disagreements sometimes expressed here is precisely over this point.

I found the "cyclops vs "stereo" image of Garry's cushion example particularly interesting. A consumer could easily be dissuaded from considering that diamond due to a concern for "leakage" (a really awful sounding word), in the straight on ASET image when unless he or she is actually is a cyclops that "leakage" does not actually constitute an issue to two eyed humans and the diamond may well be more attractive than one without that "leakage." As Karl (I think) correctly posted earlier, in fancies some amount of leakage actually enhances brightness meaning the diamond that "leaks" more can, in fact, be the diamond that, to the eye (or more accurately to the eyes), appears to "leak" less

The discussion on here makes clear just how complex these issues and how easy it is to oversimplify answers or to substitute one's own preferences for objective conclusions. And I agree with David that the use of pejorative labels is part of the problem. It is disingenuous to claim that by saying one diamond has more"leakage" than another you are stating a fact rather than implying that one diamond is gemological inferior to the other (which is not a fact).

 

[diagem]

Dont have a real Aset of this stone handy but do have this interesting image: same Diamond, same lighting environment and same camera position.
-left image, bottom lit strong white light.
-right image diamond on solid background.
can you see the interesting difference?

Diagem,



I don't really understand the lighting in those photographs. The culet(leakage) is dark in the black background image but the corners of the table (outlined in red) that I would also expect to also be darker than the white background one are not. Further it seems like both black and white images are being backlit because I see physical facets not virtual facets and thus the pictures have no direct correlation to ASET.

but..., the real Aset image should be almost identical to the DC one I posted above...

The crucial area to look at as you pointed out is on the corners of the table, there should not be so much grey in the photographed ASET image allowing for better resolution of colors in that region.

MD, these are two simple face-up shots in a closed white light environment. One is backlit (white) the other black (solid background). No photoshop!
I am trying to show that even if in AGSL's grading world the world is lit up from above (e.g. >45 deg), there is light which enters the diamond from right below the 45 deg points. This Diamond is a perfect example for that phenomena. It was designed to emphasize a specific effect (center red star shape), and it was possible by us positively utilizing these forced areas (4 corners of the table) where AGSL automatically deducts as leakage.
Obviously it's not leakage per-se or as we would expect leakage to react to light. In this specific case, these are symmetrical virtual facets reflecting low (just below the girde) light and are an integral part of this design. Deducting the same grade value as windowed leakage is erred in my opinion.

Here is a so-so image of the actual Aset (phone camera, sorry).

 

[MelisendeDiamonds]

here is light which enters the diamond from right below the 45 deg points.

I am still not certain what you mean by just below the 45 degree point.

Which colored arrow is closest to what you are referring to?, if its the grey arrows that is negative numbers like -5 or -10.
The white arrows are like -0 on one and -45 or so on the other.

If its the green arrow that is just below +45. If its the red its above <+45.
Are you talking about rays that are pointed to by the grey arrows?

 

[Garry H (Cut Nut)]

I think this comment from Garry bears repeating;

"While it has a little bowtie effect, overall its a good e.g. of crushed ice. Its nice, but i prefer the fire and brilliance of the cushion cuts that Sergey and Yuri have designed, and love the scintillation of some of them."

Garry is expressing his personal preference not scientifically verifiable superiority of one style over the other. I think the heart of the disagreements sometimes expressed here is precisely over this point.

I found the "cyclops vs "stereo" image of Garry's cushion example particularly interesting. A consumer could easily be dissuaded from considering that diamond due to a concern for "leakage" (a really awful sounding word), in the straight on ASET image when unless he or she is actually is a cyclops that "leakage" does not actually constitute an issue to two eyed humans and the diamond may well be more attractive than one without that "leakage." As Karl (I think) correctly posted earlier, in fancies some amount of leakage actually enhances brightness meaning the diamond that "leaks" more can, in fact, be the diamond that, to the eye (or more accurately to the eyes), appears to "leak" less

The discussion on here makes clear just how complex these issues and how easy it is to oversimplify answers or to substitute one's own preferences for objective conclusions. And I agree with David that the use of pejorative labels is part of the problem. It is disingenuous to claim that by saying one diamond has more"leakage" than another you are stating a fact rather than implying that one diamond is gemological inferior to the other (which is not a fact).

Stan I have a great appreciation for people who have different taste in diamonds. I would prefer we sold many more fancy cuts; round diamonds have become so commoditized. In our article in Rap:
"The Cut Group’s goal is to design beautiful new cuts and improve existing cuts. Using a music analogy, let’s add “jazz” and “rock” to the current narrow range of “classics.”

The crushed ice cushion I referred too from the MSS stones has some attraction. However I think the number of people who would choose the stone with the 2 sets of 3 images that you are referring to would be very small if they had other stones to compare in a side by side comparison.

I also think the leakage Karl mentioned contributes to contrast in step cuts. The leakage in the table of that cushion would not in my opinion contribute to the diamonds beauty in any positive sense. It would look like a huge fisheye.

 

[diagem]

here is light which enters the diamond from right below the 45 deg points.

I am still not certain what you mean by just below the 45 degree point.

Which colored arrow is closest to what you are referring to?, if its the grey arrows that is negative numbers like -5 or -10.
The white arrows are like -0 on one and -45 or so on the other.

If its the green arrow that is just below +45. If its the red its above <+45.
Are you talking about rays that are pointed to by the grey arrows?

Oops, sorry for the confusion (my bad). Of course I meant slightly below the 0 (e.g. -3 to -5).

 

[Karl_K]

I also think the leakage Karl mentioned contributes to contrast in step cuts. The leakage in the table of that cushion would not in my opinion contribute to the diamonds beauty in any positive sense. It would look like a huge fisheye.

It can add contrast in any diamond, in a modern RB the small leakage points add contrast. The way to eliminate them(painting/digging) has a negative impact on scintillation.
What it comes down to is where, how much, does it flash, is it a worthwhile compromise or just a sign of a less than optimal design. For example real leakage like a window which is rare in diamonds will never flash where a facet drawing light just under the girdle is likely to flash with tilt. The further down the pavilion it draws light the less likely it is to flash. ASET/IS do not give any idea of where it is drawing light for "leakage" other than somewhere on the pavilion.