Light leakage, how can you tell in real life?

[Rockdiamond]

I think I've got a good handle on how to frame my point.
We know how to judge which cut is most brilliant- and cutters know how to strive for that.
And we know how to interpret ASET to help define the stones that are cut for maximum light performance.
How about stones cut for maximum spread?
Just like the maximum light performance stones, stones cut for maximum spread can achieve balance- or not.
When they don't they can be really bad.

When stones cut for spread do achieve the correct balance, there's tremendous scintillation to make up for the lack of fire in my opinion.
Using the ASET chart allows us to select stones for light performance works.
What tools have we to offer for consumers who are looking for stones optimized for size and scintillation as opposed to light performance?
I don't have the answer at this moment, but I think it's part of where I see a problem the way ASET is currently interpreted- and consequently how leakage is discussed.

 

[Garry H (Cut Nut)]

You can see that it is possible for one eye to see all the light that comes from a diamond without obstruction from the head for very close viewing (10 inches or 25cm) because that ray will pass about 1.5 inches or 40mm from one eye to the side of the head.
Some people will claim that it means the same eye will see darkness in some facets because the head is broader (about 4 inches / 11cm) from the other side obstruction. True, but what we have discovered is that brilliance is largely a result of two very different contrast effects arriving through the channels to the eye and this conflict is settled by the brain as being lustrous and brighter.

ASET (and Ideal-scope) can therefore be argued to have too much blue (black).

 

[Garry H (Cut Nut)]

I think I've got a good handle on how to frame my point.
We know how to judge which cut is most brilliant- and cutters know how to strive for that.
And we know how to interpret ASET to help define the stones that are cut for maximum light performance.
How about stones cut for maximum spread?
Just like the maximum light performance stones, stones cut for maximum spread can achieve balance- or not.
When they don't they can be really bad.

When stones cut for spread do achieve the correct balance, there's tremendous scintillation to make up for the lack of fire in my opinion.
Using the ASET chart allows us to select stones for light performance works.
What tools have we to offer for consumers who are looking for stones optimized for size and scintillation as opposed to light performance?
I don't have the answer at this moment, but I think it's part of where I see a problem the way ASET is currently interpreted- and consequently how leakage is discussed.

You have been asked about fire. You should have had a career as a politician David.

 

[Karl_K]

Just like the maximum light performance stones, stones cut for maximum spread can achieve balance- or not.
When they don't they can be really bad.

Cutting a stone for max. spread will quickly lead to obstruction issues no matter which numbers you use for obstruction angles and it will lead to leakage as you hit critical angles. If a diamond is balanced and looks good some spread was compromised period.
Then you also compromise spread for durability by cutting a reasonable sized girdle.

There are no free lunches in diamond design! Everything is a compromise.

 

[Karl_K]

I also agree with David that the "red is better" mantra is a misleading oversimplification. Too much red around the culet of a radiant cut ASET scan is an indication that there will be a concentration of black around the culet, a sign of a poorly cut diamond that has the facets forming the culet on too high an angle. I recut such diamonds all the time likely resulting in a much more attractive radiant but very possibly with an ASET scan that some commentators here might consider less desirable because it has less of a concentration of red.

The only ones saying more red is always better are either uninformed or trying to discredit ASET.
Cut an SE/EC with a large p2 at 41 degrees. Lots of red. Nasty looking diamond in the real world.
Which is the same principle your talking about.
I teach better than more red is always better to those that have been willing to listen.
Guess what many of the prosumers here have listened!

 

[Serg]

Serg- please have a look at the top sellers in the world of Fancy Colored Diamonds.
Please notice how the most sought after fancy yellow radiant or cushion cut diamonds are cut ( crushed ice)
Please notice how these diamonds are set- in many cases the pavilion is obstructed by parts of the ring- and many times on purpose.
Look at the resulting rings.
Maybe you find this type of look to be sub-standard.
Maybe the people you showed your test felt the same way.
But Harry Winston,Tiffany, Graff, and many others are finding far different results in the real world.
The look we're calling "Crushed ice" has found wide acceptance - even if the pavilion is obstructed.
The finest fancy colored stones- the most desirable fancy colored diamonds in the world are cut this way.

Maybe there is something about this look we can classify as desirable?
Anything?

David,
when we finish discussion about Fire, Colorless Crushed Ice cuts, I am happy discuss Fancy Color diamonds.

where is your Fire definition ? what is Fire in diamond for you?

Hi Serg,
Thank you for responding.
I am constantly doing tests on diamonds- and appreciate the method you suggested.
In general I find the most important test is actually setting the diamond to see how it's light performance is affected.

My definition of fire:
To answer simply, what I see as fire in a diamond is the way it reflects the light back to my eye.
The ASET definitely can detect differences in the brilliance of the reflections, yet sometimes my eye is pleased more by reflections that ASET proves are less brilliant - such as the facets showing green in ASET.
So, if we say a round brilliant has more "fire" than a well cut radiant, we'd have to define fire better IMO

Unbelievable .

Dave ,
of course you may use any definitions, but if you Definitions are so Faraway from had been published by Labs, researches and common sense then you have publish Your private definitions in each your post.
I think Your posts mislead many consumers here just because you use wrong Words.
You need rewrite your Posts about Crushed Ice cuts ( most probably you mean Scintillation instead Fire. May be Brilliancy, "Life")

re:The ASET definitely can detect differences in the brilliance of the reflections, yet sometimes my eye is pleased more by reflections that ASET proves are less brilliant - such as the facets showing green in ASET.

Again huge misinterpretation . ASET does not show Brilliance at all. it shows direction of light sources which diamond redirect to "Cyclopean eye".
Just directions.
but ASET is effective tool when you need select diamond similar to Sample .
for example you find Nice Diamond for your Taste and receive ASET image for this diamond. then most probably you will like any other diamond with similar ASET image AND similar Cut .
via versa
for example you find Ugly diamond for your taste and receive ASET image for this diamond. then most probably you will dislike any other diamond with similar ASET image .

ASET has good consistency when you need find a diamond similar to sample and you have to check many diamonds in short time.
it can not grade diamonds if sample unknown . it is just show difference from sample in same reasonable metrics.

ASET greens means what diamond catch light sources from walls, windows directions instead ceiling light sources( red zones in ASET Image). Just directions, nothing about Brilliancy, Fire, Scintillation . So you may compare only similar ASET images for Cuts with similar proportions.

 

[Rockdiamond]

Serg- I have read and understand the AGS definition of fire. Thank you again Bryan for the link.
This can make communication between the experts on this thread possible. So WE know we're taking about the same thing.
But it changes nothing for consumers. A technical discussion of Ray tracing and stereoscopic vision will be lost on most consumers who just need a better way to use ASET images.
A lot more good points raised. I'll respond more completely later today.

 

[teobdl]

Serg and Garry:
Has your two-eyed approach to studying the perceived life of a diamond led you to conceive novel cuts? Alternatively, have you become more open to or more critical of certain cuts that are generally regarded as poor or good (respectively).

Or has the effort, to this point, still in the phase of increasing our understanding of human two-eyed perception?

 

[Serg]

Serg and Garry:
Has your two-eyed approach to studying the perceived life of a diamond led you to conceive novel cuts?

Yes.

Alternatively, have you become more open to or more critical of certain cuts that are generally regarded as poor or good (respectively).

may be.

Or has the effort, to this point, still in the phase of increasing our understanding of human two-eyed perception?

Yes.
it is not necessary to have exact model of human stereo vision to create cuts which better use human stereo vision then RBC.

 

[Texas Leaguer]

Serg and Garry:
Has your two-eyed approach to studying the perceived life of a diamond led you to conceive novel cuts? Alternatively, have you become more open to or more critical of certain cuts that are generally regarded as poor or good (respectively).

Or has the effort, to this point, still in the phase of increasing our understanding of human two-eyed perception?

Great questions teobdl. Wondering the same myself. That is the kind of inquiry that will make the thread constructive. Thanks.

 

[Texas Leaguer]

Serg/Garry,
Is the "dominant eye" phenomenon a factor in the equation? My understanding is that is a brain thing. Both eyes see (stereo) but information from the dominant eye takes priority. Does that not make viewing a diamond a bit more mono than stereo?

(I'm referring to the effect that you see when you hold your thumb and index fingers together in a circle in front of your face and look through it to a distant object. Then close one eye. If you see the same view, the open eye is dominant. If you then close the dominant eye holding you fingers fixed and the non-dominant eye open, the view shifts at a dramatic angle.)

 

[Serg]

Serg/Garry,
Is the "dominant eye" phenomenon a factor in the equation? My understanding is that is a brain thing. Both eyes see (stereo) but information from the dominant eye takes priority. Does that not make viewing a diamond a bit more mono than stereo?

(I'm referring to the effect that you see when you hold your thumb and index fingers together in a circle in front of your face and look through it to a distant object. Then close one eye. If you see the same view, the open eye is dominant. If you then close the dominant eye holding you fingers fixed and the non-dominant eye open, the view shifts at a dramatic angle.)

No< if you mean "static Dominant eye". It is much more complex than "Dominant eye model"
Just simplest sample: take some Cushion with VF's bigger than in Crushed Ice and less than in RBC. Check Fire in light Environment for good Fire.

Close left eye, calculate colourful flashes
Close right eye, calculate colourful flashes
open both eyes, calculate colourful flashes.

then do it for RBC.

For cushion by both eyes you will see in 1.5-2times more flashes then by one eye.
for round you will see similar number flashes by one and by both eyes.

there are more complex samples which show that Dominate eye model is to simple.
for example Stereo rivalry is important to create great Brilliancy ( in static Dominate model it is not possible)

 

[Karl_K]

Serg/Garry,
Is the "dominant eye" phenomenon a factor in the equation? My understanding is that is a brain thing. Both eyes see (stereo) but information from the dominant eye takes priority. Does that not make viewing a diamond a bit more mono than stereo?

(I'm referring to the effect that you see when you hold your thumb and index fingers together in a circle in front of your face and look through it to a distant object. Then close one eye. If you see the same view, the open eye is dominant. If you then close the dominant eye holding you fingers fixed and the non-dominant eye open, the view shifts at a dramatic angle.)

I think that Serg underestimates the effect of dominant eye.
Particularly in people like me who are very very strongly one eye dominant due to much better eye sight in one eye.
One eye even corrected has been so much better for so long that my brain uses the other much more than most people.
In fact if text is so small that up close it is clear only to the nearsighted eye I can make out the letters fine and it looks crisp but I can only read/comprehend it with difficulty because my brain is so reliant on the other eye which is not seeing it clearly.
This is not that uncommon from what the eye doc says.
Then again until you understand perfect vision and diamonds you can't account for the exceptions.
So I understand where Serg is coming from.

 

[Texas Leaguer]

Serg/Garry,
Is the "dominant eye" phenomenon a factor in the equation? My understanding is that is a brain thing. Both eyes see (stereo) but information from the dominant eye takes priority. Does that not make viewing a diamond a bit more mono than stereo?

(I'm referring to the effect that you see when you hold your thumb and index fingers together in a circle in front of your face and look through it to a distant object. Then close one eye. If you see the same view, the open eye is dominant. If you then close the dominant eye holding you fingers fixed and the non-dominant eye open, the view shifts at a dramatic angle.)

No< if you mean "static Dominant eye". It is much more complex than "Dominant eye model"
Just simplest sample: take some Cushion with VF's bigger than in Crushed Ice and less than in RBC. Check Fire in light Environment for good Fire.

Close left eye, calculate colourful flashes
Close right eye, calculate colourful flashes
open both eyes, calculate colourful flashes.

then do it for RBC.

For cushion by both eyes you will see in 1.5-2times more flashes then by one eye.
for round you will see similar number flashes by one and by both eyes.

there are more complex samples which show that Dominate eye model is to simple.
for example Stereo rivalry is important to create great Brilliancy ( in static Dominate model it is not possible)

Very interesting. So I guess the advice for cushion owners is - "for best results, don't blink!"

 

[teobdl]

Is it possible to make a table of the permutations of simultaneously received rays and the result on human perception? Does duration matter?
This does not account for the fact that virtual facets may differ in size and even light source at the same real location on a diamond. This, and others, may make this kind of table impossible.

For example, maybe something like this (not suggesting this is accurate):
Left Eye . . . . . . . . Right Eye. . . . . Result
White flash. . . . . . .White flash. . . . Bright flash
Leakage . . . . . . . . White flash. . . .Even More intense bright flash
Red flash. . .. .. .. ..Red flash . . . . . .Red flash
Leakage . . . . . . .. . Red light. . . . . . More intense Red flash
Green flash . . . .. . .. Red flash. . . . . .??

Very interested to know. I'm sorry if it's discussed on the **.ru website. Can't access that site at the moment.

 

[Texas Leaguer]

Serg/Garry,
Is the "dominant eye" phenomenon a factor in the equation? My understanding is that is a brain thing. Both eyes see (stereo) but information from the dominant eye takes priority. Does that not make viewing a diamond a bit more mono than stereo?

(I'm referring to the effect that you see when you hold your thumb and index fingers together in a circle in front of your face and look through it to a distant object. Then close one eye. If you see the same view, the open eye is dominant. If you then close the dominant eye holding you fingers fixed and the non-dominant eye open, the view shifts at a dramatic angle.)

I think that Serg underestimates the effect of dominant eye.
Particularly in people like me who are very very strongly one eye dominant due to much better eye sight in one eye.
One eye even corrected has been so much better for so long that my brain uses the other much more than most people.
In fact if text is so small that up close it is clear only to the nearsighted eye I can make out the letters fine and it looks crisp but I can only read/comprehend it with difficulty because my brain is so reliant on the other eye which is not seeing it clearly.
This is not that uncommon from what the eye doc says.
Then again until you understand perfect vision and diamonds you can't account for the exceptions.
So I understand where Serg is coming from.

Crazy is'nt it? It must seem to you researchers like this is an exercise in chasing rainbows (almost literally!). Just when you think you are close to nailing it down with ray tracing, the quest leads you into the realm of neuroscience. That's when you get into some seriously deep yogurt.

 

[Texas Leaguer]

Is it possible to make a table of the permutations of simultaneously received rays and the result on human perception? Does duration matter?
This does not account for the fact that virtual facets may differ in size and even light source at the same real location on a diamond. This, and others, may make this kind of table impossible.

For example, maybe something like this (not suggesting this is accurate):
Left Eye . . . . . . . . Right Eye. . . . . Result
White flash. . . . . . .White flash. . . . Bright flash
Leakage . . . . . . . . White flash. . . .Even More intense bright flash
Red flash. . .. .. .. ..Red flash . . . . . .Red flash
Leakage . . . . . . .. . Red light. . . . . . More intense Red flash
Green flash . . . .. . .. Red flash. . . . . .??

Very interested to know. I'm sorry if it's discussed on the **.ru website. Can't access that site at the moment.

I'm not qualified to comment on the validity of the approach you suggest, although it does sound logical. But I will say I very much like how many times in your table whiteflash is mentioned.

 

[Rockdiamond]

Just like the maximum light performance stones, stones cut for maximum spread can achieve balance- or not.
When they don't they can be really bad.

Cutting a stone for max. spread will quickly lead to obstruction issues no matter which numbers you use for obstruction angles and it will lead to leakage as you hit critical angles. If a diamond is balanced and looks good some spread was compromised period.
Then you also compromise spread for durability by cutting a reasonable sized girdle.

There are no free lunches in diamond design! Everything is a compromise.

It's true Karl- everything in design IS a compromise.
There are indeed facet designs that are cut for spread. Well cut spready stones like this use scintillation to alleviate the leakage issues you mention.
Yes, tilt the spready stone and you get a window at less of an angle to the eye than a stone cut for light performance
But this can be optimized so that you need more tilt to get the window to appear.
Yes some spread is compromised in every well cut diamond. The question is how much do we optimize for spread, and how much for LP. And there is no right answer. We're getting into an aspect that purely subjective.

About all the technical issues being raised- they are interesting- but certainly not necessary for a consumer to learn how to buy well cut diamonds.

In fact, raising such issues will make it MORE difficult for consumers to understand what we're discussing.
The OP asked about leakage in REAL LIFE.

 

[Karl_K]

Crazy is'nt it? It must seem to you researchers like this is an exercise in chasing rainbows (almost literally!). Just when you think you are close to nailing it down with ray tracing, the quest leads you into the realm of neuroscience. That's when you get into some seriously deep yogurt.

Yep it is crazy. Which is why any diamond design is not a sure thing until it is cut and seen in the real world over a period of time by different people. Comparing it to known pleasing samples in virtual helps get it right before cutting of course but there will always be some amount of doubt until it is cut.

 

[Karl_K]

Is it possible to make a table of the permutations of simultaneously received rays and the result on human perception? Does duration matter?
This does not account for the fact that virtual facets may differ in size and even light source at the same real location on a diamond. This, and others, may make this kind of table impossible.

For example, maybe something like this (not suggesting this is accurate):
Left Eye . . . . . . . . Right Eye. . . . . Result
White flash. . . . . . .White flash. . . . Bright flash
Leakage . . . . . . . . White flash. . . .Even More intense bright flash
Red flash. . .. .. .. ..Red flash . . . . . .Red flash
Leakage . . . . . . .. . Red light. . . . . . More intense Red flash
Green flash . . . .. . .. Red flash. . . . . .??

Very interested to know. I'm sorry if it's discussed on the **.ru website. Can't access that site at the moment.

I wish it were that simple however it is far more complex.
Duration is a critical component.
What has to happen for you to see one flash of light from a diamond?
There has to be light in an area that the diamond can return it to the eye/s.
It has to hit one or both eyes.
It has to last long enough for it to be perceived.
It has to be bright enough to stand out.
It has to catch your attention.

But,
While the diamond is sending out that one flash you are seeing it is also likely sending out thousands of others no one is seeing but they do exist.
A well cut diamond will send a larger percentage in a way that has a chance of being seen by the wearer than a less well cut diamond.

but..
I call it the 3 people rule.
3 people standing side by side with the center person holding the diamond at arms length even with their middle. Each person will see different virtual facets, different patterns, different flashes, and one could be seeing brightness and the other 2 mainly fire or any combination.

 

[Karl_K]

In fact, raising such issues will make it MORE difficult for consumers to understand what we're discussing.
The OP asked about leakage in REAL LIFE.

The first couple posts answered the OPs question. I checked that it was answered before diving in.
Consumers understand far more than you think.

 

[teobdl]

I am trying to expand upon the example Garry brought up of a single observer and the effects of contrasting inputs to both eyes. BTW, one scenario I left out is Garry's: obstruction in one eye, white flash in the other eye.

You can see that it is possible for one eye to see all the light that comes from a diamond without obstruction from the head for very close viewing (10 inches or 25cm) because that ray will pass about 1.5 inches or 40mm from one eye to the side of the head.
Some people will claim that it means the same eye will see darkness in some facets because the head is broader (about 4 inches / 11cm) from the other side obstruction. True, but what we have discovered is that brilliance is largely a result of two very different contrast effects arriving through the channels to the eye and this conflict is settled by the brain as being lustrous and brighter.

ASET (and Ideal-scope) can therefore be argued to have too much blue (black).

 

[Rockdiamond]

Hi Karl,
Please don't make any assumptions about what I think.
That could be very dangerous
Plus I speak to hundreds, if not thousands of real consumers every month.
I have a pretty good idea about consumers, and how they think.

And the OP's questions have not been properly answered. Or the discussion ab out leakage, and spread versus light performance

 

[Rockdiamond]

Karl- to your point, about how much consumers know-
1) any consumer reading this site has a HUGE advantage over someone who has not read it when they walk into a jewelry store.
They will have learned how to cut through a lot of the horrendous BS sales practices that are all too common-like the seller who says
"GIA? Nobody buys those anymore, they're way overpriced.
I have this amazing D/VVS1 certified by Joe's gem lab, a real bargain"
Unfortunately, after speaking to all these many many thousands of folks over the years, too many never learn about the gem lab scam. PS readers are well covered on that front.
2) along the way, this amazing education can be taken to a point that it looses a bit of perspective.
For example- not every jeweler with integrity, and that also understands cut, uses ASET.

We can debate if they should- but the fact is, by advising consumers to avoid anyone not using ASET, it eliminates some very good options for people.
And, the whole issue of spread versus light performance, and how to define a balance that's right for an individual, as opposed to the people advising that individual. The issue of green on the aset- and how to interpret. It's far more difficult to use ASET to find well cut stones optimized for spread versus using ASET to assess stones cut for light performance.
Readers educated using that chart calling the ASET on the left " Ex" and the one far right "Fair" have been given incorrect advice.
Stan ( Radaintman) has not spent as much time here as I-, I think he deserves a bit of a break for his comments. Having spent more time here I have indeed seen improvements in the way advice is given- but there's still a long way to go

 

[Dancing Fire]

David
The problem is that I can't afford to have a dozen stones ship to my house to play with for a month and compare all the stones next to each other, nor can I afford to pay for all the shipping cost, so IMO most PSers must try to weed out the poorly cut stones with tools and the lab report information.

 

[Texas Leaguer]

About all the technical issues being raised- they are interesting- but certainly not necessary for a consumer to learn how to buy well cut diamonds.

In fact, raising such issues will make it MORE difficult for consumers to understand what we're discussing.
The OP asked about leakage in REAL LIFE.

David,
Please think about what you are saying and who you are saying it to. This forum is read by an extremely intelligent population, many of whom have scientific backgrounds. They are interested in following and often contributing to technical discussion.

Those who are not interested in a particular discussion, or to whom the discussion is not relevant, can easily disconnect from a thread.

Frankly, it is insulting to suggest that discussion of the technical aspects of diamonds "makes it more difficult for consumers to understand what we're discussing". That is one of the positions you should consider giving a rest.

 

[Rockdiamond]

HI DF!
That is a great point. If a person wants a stone optimized for light performance, the tools work.
If a person wants a stone cut to look larger, not optimized for light performance- rather optimized for a different sort of light performance, the tools are far more difficult to use.
I have been doing a lot of looking at a lot of diamonds and putting them on an aset during the past few days.
I was looking at a pear shape, cut for size.
A lot of green in the aset- and red in at the widest point- therefore the ASET indicates a difference in light performance at the tip and "butt" as compared to the center.
If it was blue, we'd be looking at a bow tie- but the red I see in ASET does not show as a different sort light performance when viewed with the naked eye. The particular pear shape I was using has a very even "crushed ice" sort of look.
Point is- if I used the aset I'd eliminate a very well cut, attractive stone that has a lot of spread for it's weight.
But not optimal light performance.
That's the compromise I'm speaking of.

 

[Rockdiamond]

Hi Bryan,
There's actually a section called "Diamond Research" for highly technical discussions.
My impression was Rocky Talky was primarily about practical knowledge.
And I definitely agree that we should all be sensitive to the other person's experience, and opinion.

 

[Serg]

Is it possible to make a table of the permutations of simultaneously received rays and the result on human perception? Does duration matter?
This does not account for the fact that virtual facets may differ in size and even light source at the same real location on a diamond. This, and others, may make this kind of table impossible.

For example, maybe something like this (not suggesting this is accurate):
Left Eye . . . . . . . . Right Eye. . . . . Result
White flash. . . . . . .White flash. . . . Bright flash
Leakage . . . . . . . . White flash. . . .Even More intense bright flash
Red flash. . .. .. .. ..Red flash . . . . . .Red flash
Leakage . . . . . . .. . Red light. . . . . . More intense Red flash
Green flash . . . .. . .. Red flash. . . . . .??

Very interested to know. I'm sorry if it's discussed on the **.ru website. Can't access that site at the moment.

re: Does duration matter?

Yes, Duration is very important
1) Subjective brightness depends from Flash frequency ( flashes with frequency 2-10Hz looks more bright than flashes with same intensity but with longer duration . It is one of reasons why lighthouse uses flashes instead continues light.
2) suppose you have 2 difference cuts. one cut has flashes with long duration , other cut has flashes with 2 times less duration
and both cuts have same sums :Area( of Flash)*duration .
even if 1st cut has 50% more flashes for each fixed position, in dynamic you will see more flashes in 2d cut.

 

[teobdl]

Great, Serg. Thank you-that's very helpful.

If I'm not misunderstanding things, I think Serg's research may help bolster RD's point about the role leakage might play in the look of a diamond -- it may even enhancing the look of certain diamonds (specifically, crushed ice). And it further emphasizes the fact that quantifying the threshold at which leakage detracts from a diamond's beauty is so difficult.