Light leakage, how can you tell in real life?

[Rockdiamond]

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.

THANK YOU!!!!
Perfectly stated.

 

[Karl_K]

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.

Allowing some leakage and some green can make for an overall brighter diamond in some cases.
I gain 10% overall brightness on Octavia that way and it has been cut without it to verify it by eye and the diamond was quickly fixed to include it.
David however takes that fact that it may be good to include it way too far sometimes.
That it is better in one particular configuration does not mean it will be so in another.

 

[Rockdiamond]

Karl, all due respect but till we sit down together and look at diamonds, it is not at all fair to make any assumptions about how I analyze leakage in diamonds.

 

[Texas Leaguer]

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.

I was reading it that way too. I would be interested to see if Serg thinks that's a fair takeaway.

But how would facet size and sum of flash area relate? That is, would a 2 chevron and 4 chevron princess of the same size and proportions have the same sum of flash area? The 4 chev would have more frequent flashes, and more of a crushed ice appearance. Would it be brighter simply by virtue of flash frequency? If so, is there any kind of relationship that can be stated between scintillation and perceived brightness?

 

[Rockdiamond]

Bryan,
Here's where I can answer from a practical standpoint.
From a standpoint of cut, the painted facets on the pavilion of a stone with more bounces ( crushed ice) allows the cutter a lot of freedom to make subtle pavilion variations that create large difference in light return through the table.
So there's no consistent correlation to be drawn in the market between the amount of chevrons and the resulting light performance.
I'm sure a cut can be designed to act one way or the other if it was done in a precise manner- but in the real world there's a lot of variation from one fancy shape to the next.

 

[Karl_K]

Karl, all due respect but till we sit down together and look at diamonds, it is not at all fair to make any assumptions about how I analyze leakage in diamonds.

I am not talking about how you analyze diamonds in person its your advice you give others and what you post here that I question.
Just because you find one diamond with some leakage that looks better than one with no leakage does not mean that will always be the case. Even if you find 100 of a particular configuration that works that way does not mean it applies to another configuration.

 

[Karl_K]

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.

I was reading it that way too. I would be interested to see if Serg thinks that's a fair takeaway.

But how would facet size and sum of flash area relate? That is, would a 2 chevron and 4 chevron princess of the same size and proportions have the same sum of flash area? The 4 chev would have more frequent flashes, and more of a crushed ice appearance. Would it be brighter simply by virtue of flash frequency? If so, is there any kind of relationship that can be stated between scintillation and perceived brightness?

Interesting question.. Which is brighter..
Faster smaller flashes or slower larger flashes given that the lighting allows them both to have effective virtual facets.
It is going to be lighting dependent.

 

[CanuckAB]

David,

I must admit that I find your opinion of consumers offensive. Yes, most consumers know very little about diamonds but that does not mean that some of them are not interested in learning. And I find that more and more people are looking to the internet to educate themselves prior to making this expensive a purchase. I get the feeling that you are the kind of person who's attitude is: Trust me. I know about diamonds and this is the stone or stones you should consider. You wouldn't understand the complexaties so leave it to me. I would be walking out of your store by now.

I've learned a lot from this site. The people here are trying to help consumers make safe decisions so that they'll end up with gorgeous results. Even if a consumer sees a stone in person, the only way WE can help that person is if we have access to those tools because WE can't see the stone. I personally only feel comfortable helping with MRBs at this point and refrain from offering help with other cuts as my knowledge is too limited about them. I do read those threads though as I wish to increase that knowledge.

Personally, I was never drawn to diamonds before and would choose a coloured stone over a diamond any day. My feeling was that they were shiney white stones and they left me cold. Granted, my only exposure was to mall stores and a few jewellery stores. Late last year I accidentally came across a diamond that blew me away because of it's fire. Suddenly I'm obsessed with diamonds! That is how I ended up here, researching how this one diamond could have made me fall in love! I'm intelligent enough to know that what I like in a diamond will not be found in the GIA XXX or AGS0 stock and for me that is just fine. My GIA VG FIC cut 1ct scores a .7 HCA and, as I was able to evaluate it in person, no tools were necessary for me to close the purchase. I have new projects in the works and I'm driving my jeweller crazy because I'm rejecting GIA XXX stones that are steep deeps etc. You can keep your brilliant diamonds. I'm in love with fire!

Now back to the topic of light leakage, which I find fascinating or I wouldn't still be reading this thread.

 

[Serg]

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.

I was reading it that way too. I would be interested to see if Serg thinks that's a fair takeaway.

But how would facet size and sum of flash area relate? That is, would a 2 chevron and 4 chevron princess of the same size and proportions have the same sum of flash area? The 4 chev would have more frequent flashes, and more of a crushed ice appearance. Would it be brighter simply by virtue of flash frequency? If so, is there any kind of relationship that can be stated between scintillation and perceived brightness?

There is a optimal range for VF's size. To keep it always in optimal range you have to use different cuts for different diamond size.
also answer depends which balance between Fire and Brilliancy do you prefer.
Usually Crushed Ice cuts have to small VF's size to show some important phenomenas of diamond beauty .
on opposite side is Emerald cut. Good balance is between Emerald and Crushed Ice cuts.
Of course Crushed Ice cuts is much more easy for cutters.( it hide cutters mistakes)

 

[Rockdiamond]

Karl, all due respect but till we sit down together and look at diamonds, it is not at all fair to make any assumptions about how I analyze leakage in diamonds.

I am not talking about how you analyze diamonds in person its your advice you give others and what you post here that I question.
Just because you find one diamond with some leakage that looks better than one with no leakage does not mean that will always be the case. Even if you find 100 of a particular configuration that works that way does not mean it applies to another configuration.

HI Karl,
I do not advise others on PS about specific diamonds.
If you don't agree with what I've posted here, of course that's your right.
You are however completely making my point.
Just because one stone that shows leakage in ASET is beautiful does not mean all are.
Just because a stone does not show leakage also does not mean it's beautiful.

 

[teobdl]

I don't want to speak for David, but in his defense, I didn't read him as suggesting customers are dumb, but rather it was 1) a reminder to not incite fear about minutia and 2) not properly using the more advanced tools can lead to even worse decisions than if they didn't have them at all. In that vain, I took it as more of a warning to the experts (and aspiring experts) than an attack on customers.

 

[Texas Leaguer]

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.

I was reading it that way too. I would be interested to see if Serg thinks that's a fair takeaway.

But how would facet size and sum of flash area relate? That is, would a 2 chevron and 4 chevron princess of the same size and proportions have the same sum of flash area? The 4 chev would have more frequent flashes, and more of a crushed ice appearance. Would it be brighter simply by virtue of flash frequency? If so, is there any kind of relationship that can be stated between scintillation and perceived brightness?

There is a optimal range for VF's size. To keep it always in optimal range you have to use different cuts for different diamond size.
also answer depends which balance between Fire and Brilliancy do you prefer.
Usually Crushed Ice cuts have to small VF's size to show some important phenomenas of diamond beauty .
on opposite side is Emerald cut. Good balance is between Emerald and Crushed Ice cuts.
Of course Crushed Ice cuts is much more easy for cutters.( it hide cutters mistakes)

I would think there is also an optimal frequency with regard to impact on brightness. For instance, in your example of the lighthouse, they don't use a steady light because a flashing light looks brighter. But the mirror rotates rather slowly (long duration each flash). At some point increasing the frequency of the flash would result in sub-optimal brightness. In addition diminished fire, Is that not one of the problems with the crushed ice look?

 

[Serg]

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.

I was reading it that way too. I would be interested to see if Serg thinks that's a fair takeaway.

But how would facet size and sum of flash area relate? That is, would a 2 chevron and 4 chevron princess of the same size and proportions have the same sum of flash area? The 4 chev would have more frequent flashes, and more of a crushed ice appearance. Would it be brighter simply by virtue of flash frequency? If so, is there any kind of relationship that can be stated between scintillation and perceived brightness?

There is a optimal range for VF's size. To keep it always in optimal range you have to use different cuts for different diamond size.
also answer depends which balance between Fire and Brilliancy do you prefer.
Usually Crushed Ice cuts have to small VF's size to show some important phenomenas of diamond beauty .
on opposite side is Emerald cut. Good balance is between Emerald and Crushed Ice cuts.
Of course Crushed Ice cuts is much more easy for cutters.( it hide cutters mistakes)

I would think there is also an optimal frequency with regard to impact on brightness. For instance, in your example of the lighthouse, they don't use a steady light because a flashing light looks brighter. But the mirror rotates rather slowly (long duration each flash). At some point increasing the frequency of the flash would result in sub-optimal brightness. In addition diminished fire, Is that not one of the problems with the crushed ice look?

VF's may be Big or Small, Slow and Fast.
Usually if VF's are Big then they are Slow, of if VF's Small then they are Fast( but possible Big-Fast and may be Small-Slow)

Human eye can not recognise Color if Flash small and fast as in Crushed Ice cut. if VF's are Bigger or have longer duration than in Crushed IC then Human eye see Fire much better.

Also difference between 100 flashes and 120 flashes is much less visible than difference between 20 and 40 flashes( and even between 5 and 10).

so if we reduce of size VFs in 2 times to increase number of flashes in 2 times then total appearance may be better or worse depends from primary size.
roughly if we had 1 big flashes in 2 seconds and split it in to 2 flashes in same 1 second( 0.5 second each and half area from primary flash) then we increase Beauty.

but if we spilt 100 small and fast Flashes and receive 200 smaller and faster flashes we decrease Beauty.
you will not see big difference between 100 and 200 flashes, but you will easy see that each flash is smaller, less saturated,..
from certain VF's size diamond appearance loose something important and increasing number of tiny flashes can not compensate it

 

[Rockdiamond]

Canuck-I have dedicated a lot of my life to educating consumers- differently than a lot of what we're speaking about here- bt that in itself is an interesting part of the discussion.
It's not necessary to know what "painting and digging" are to buy a well cut diamond.
Yet many regular PS reader know exactly what I'm referring to.
Most jewelers don't know what we're talking about.
I get that- and it's an amazing place.
My apologies if it seemed I don't respect the highly technical studies- I do.
My point is that you don't have to get that technical to buy a well cut diamond and a lot of consumers don't want to get that technical.

 

[Karl_K]

I would think there is also an optimal frequency with regard to impact on brightness. For instance, in your example of the lighthouse, they don't use a steady light because a flashing light looks brighter. But the mirror rotates rather slowly (long duration each flash). At some point increasing the frequency of the flash would result in sub-optimal brightness. In addition diminished fire, Is that not one of the problems with the crushed ice look?

I'm not sure lighthouse is a good comparison.
The mirrors turn slowly so that you have time to get your bearings.
They turned because beams of light using lenses were the only way to get a bright enough light.
Modern lighthouses with electronic strobes flash faster than the the old type if they use flashes rather than always on light bulbs.
They mostly use a long on time and a short off time.
They can do so because the strobe is bright enough not to need a directional lens like the old lamp then arc lights then incandescent or halogen/sodium bulbs.

 

[Karl_K]

There is a optimal range for VF's size. To keep it always in optimal range you have to use different cuts for different diamond size.
also answer depends which balance between Fire and Brilliancy do you prefer.
Usually Crushed Ice cuts have to small VF's size to show some important phenomenas of diamond beauty .
on opposite side is Emerald cut. Good balance is between Emerald and Crushed Ice cuts.
Of course Crushed Ice cuts is much more easy for cutters.( it hide cutters mistakes)

I would think there is also an optimal frequency with regard to impact on brightness. For instance, in your example of the lighthouse, they don't use a steady light because a flashing light looks brighter. But the mirror rotates rather slowly (long duration each flash). At some point increasing the frequency of the flash would result in sub-optimal brightness. In addition diminished fire, Is that not one of the problems with the crushed ice look?

VF's may be Big or Small, Slow and Fast.
Usually if VF's are Big then they are Slow, of if VF's Small then they are Fast( but possible Big-Fast and may be Small-Slow)

Human eye can not recognise Color if Flash small and fast as in Crushed Ice cut. if VF's are Bigger or have longer duration than in Crushed IC then Human eye see Fire much better.

Also difference between 100 flashes and 120 flashes is much less visible than difference between 20 and 40 flashes( and even between 5 and 10).

so if we reduce of size VFs in 2 times to increase number of flashes in 2 times then total appearance may be better or worse depends from primary size.
roughly if we had 1 big flashes in 2 seconds and split it in to 2 flashes in same 1 second( 0.5 second each and half area from primary flash) then we increase Beauty.

but if we spilt 100 small and fast Flashes and receive 200 smaller and faster flashes we decrease Beauty.
you will not see big difference between 100 and 200 flashes, but you will easy see that each flash is smaller, less saturated,..
from certain VF's size diamond appearance loose something important and increasing number of tiny flashes can not compensate it

That makes perfect sense to me.

 

[Rockdiamond]

Serg- thank you for taking the time to write that- it's informative.
I agree with everything you wrote, till you used the word "beauty"
That is where we have to separate physical description of light behavior from human taste.

 

[Serg]

Figure 3.28 Apparent brightness of flashes with various luminance, as a function of flash duration. Source: (Broca and Sulzer data from Kalloniatis and Luu. WebVision).

"Dynamic Contrast and Temporal Effects
When observing a static diamond, we see practically no “life” in it: the brilliance effect is highly damped, while any static flashes do not appear very attractive. One of the reasons for this is the absence of dynamic con- trast. Dynamic contrast is associated with the effect of enhancement of the perceived brightness with temporal changes of the observed pattern. One of its manifestations is the Broca-Sulzer phenomenon of apparent amplification of a short-duration flash (Fig. 3.28, Kalloniatis and Luu, WebVision). The results of experiments with a blinking diode published in this paper show that when the flash duration is from 50 to 100 ms, the diode seems much brighter than when in continuous operation.
This phenomenon is caused by a rapid growth of excitation of retinal neurons at the sudden appearance of a signal, which is known as overshooting. It suggests a mechanism of how to increase scintillation of a diamond: it is advisable for the diamond cut shape to gather rays coming at different angles in a single crown area. Such cuts will show stronger flash dynamics with small natural rocking of the diamond, making the flashes look apparently brighter.
Dynamic contrast greatly affects not only bright flashes, but low dynamic range images as well, this fact being confirmed by a variety of studies of spatio-temporal contrast (Burbeck and Kelly, 1980; Kal- loniatis and Luu., WebVision). There are several facts known about the processes involved in perception of dynamic images.

To detect light flashes, one by one, an appropriate integration
time (10-15 ms for cones) is required (Kalloniatis and Luu. WebVision).
If the signal remains constant with time, the response to it becomes compromised. This feature is caused by physiological processes of neural adaptation, which are described in (Schmidt and Thews, 1989). The above two processes are responsible for the band-pass temporal response of vision, which passes middle frequencies, but dampens low and high frequencies. This is seen in the bell-like shape of the plots of Temporal Contrast Sensitivity Function (TSF) for a flickering signal under different light adaptation conditions, shown in Fig. 3.29. In the case of photopic vision, our perception is most sensitive to signals blinking at a frequency of 15-20 Hz, with a dramatic decay in sensitivity occurring around 60 Hz.
In summary, Temporal Contrast Sensitivity greatly affects dynamic pattern contrast, and therefore Brilliance, while the Broca-Sulzer effect has a big influence on perception of flash brightness, and therefore Fire and Scintillation. The human perception of short and long-lived flashes is also influenced by a number of high-level effects as follows.
High-Level Effects of Object Perception"


The Australian Gemmologist | Third Quarter 2013 | Volume 25, Number 3

 

[Serg]

Serg- thank you for taking the time to write that- it's informative.
I agree with everything you wrote, till you used the word "beauty"
That is where we have to separate physical description of light behavior from human taste.

Dave , if we use different definitions for Fire, we may do same for Beauty.
I used Beauty here ( instead Optical performance ) because we tested it with many consumers and experts.

 

[teobdl]

I'd be interested to hear Rhino, John P, and/or Paul's thoughts on the role of leakage (as opposed to contrast) in enhancing scintillation and even perceived brilliance.

Also, it's been fun reading a 2010 thread in conjunction with the present one, particularly this post from He Who Must Not Be Named:

[quote=""He Who Must Not Be Named"|1286316980|2729512":1k7jrqxo]


I beleive this thread should be about a comprehensive discussion of ASET image interpretation in the green low angle region.
If one wants to ignore interpretation of ASET, the science behind it and move on directly to comparing ASET to subjective beauty evaluations here it is:

Objective Facts:

Small green patches sorrounded by white in ASET can show fast scintillation (abundant small pinfire flashes) in strong spot lighting or lighting with abundant lower angle sources. In other more diffuse overhead only lighting those areas can be lifeless.

Scintillation(sparkles) and brightness are two different things, a stone can have many tiny little pinfire flashes under strong spot lighting and movement but still not appear very bright.

It would be better to correlate ASET white with smaller flashes as those are the areas that create contrast.
NO direct correlation between green with smaller virtual facets or flashes.


Subjective Opinion: I don't beleive brightness has to be sacrificed for faster scintillation.

At the very least a good balance of brightness and scintillation can be achieved by proper facet alignment and design where weight saving and spread considerations do not not overpower more optimal brightness considerations.

By far the status quo in most diamonds with the marquise or pear shape outline is to save weight or to maximize spread and so they are often cut with shallow pavilions.

If we consider a continum of one simplified tradeoff:



I would say most diamonds on the market today are a 4 or 5 and the ASET would help you choose the 7,8,9,10 from the much more abundant lower numbers. Nothing wrong with going more for spread but you are trading off more intense light return to get it.

Note:

I define brightness using AGSL's definition:

For understanding the illumination appearance of a gem it is useful to think of a gem’s facets and their optical projections,
the virtual facets, as a collection of tiny prisms that direct light to an observer’s eyes. Thus brilliance(brightness) is defined as the percentage by area of such tiny prisms that can direct light to the observer’s eyes.

GIA's definition of brightness is pretty close too:

The appearance or extent of internal and external reflections of "White" light seen in a polished diamond when viewed face-up. [/quote]
From a thread started by the man the myth, RockDiamond. [URL='https://www.pricescope.com/community/threads/discussion-of-green-in-an-aset-image.150479/']https://www.pricescope.com/community/threads/discussion-of-green-in-an-aset-image.150479/[/URL]

 

[Garry H (Cut Nut)]

I'd be interested to hear Rhino, John P, and/or Paul's thoughts on the role of leakage (as opposed to contrast) in enhancing scintillation and even perceived brilliance.

Also, it's been fun reading a 2010 thread in conjunction with the present one, particularly this post from He Who Must Not Be Named:

[quote=""He Who Must Not Be Named"|1286316980|2729512":17i195re]


I beleive this thread should be about a comprehensive discussion of ASET image interpretation in the green low angle region.
If one wants to ignore interpretation of ASET, the science behind it and move on directly to comparing ASET to subjective beauty evaluations here it is:

Objective Facts:

Small green patches sorrounded by white in ASET can show fast scintillation (abundant small pinfire flashes) in strong spot lighting or lighting with abundant lower angle sources. In other more diffuse overhead only lighting those areas can be lifeless.

Scintillation(sparkles) and brightness are two different things, a stone can have many tiny little pinfire flashes under strong spot lighting and movement but still not appear very bright.

It would be better to correlate ASET white with smaller flashes as those are the areas that create contrast.
NO direct correlation between green with smaller virtual facets or flashes.


Subjective Opinion: I don't beleive brightness has to be sacrificed for faster scintillation.

At the very least a good balance of brightness and scintillation can be achieved by proper facet alignment and design where weight saving and spread considerations do not not overpower more optimal brightness considerations.

By far the status quo in most diamonds with the marquise or pear shape outline is to save weight or to maximize spread and so they are often cut with shallow pavilions.

If we consider a continum of one simplified tradeoff:



I would say most diamonds on the market today are a 4 or 5 and the ASET would help you choose the 7,8,9,10 from the much more abundant lower numbers. Nothing wrong with going more for spread but you are trading off more intense light return to get it.

Note:

I define brightness using AGSL's definition:

For understanding the illumination appearance of a gem it is useful to think of a gem’s facets and their optical projections,
the virtual facets, as a collection of tiny prisms that direct light to an observer’s eyes. Thus brilliance(brightness) is defined as the percentage by area of such tiny prisms that can direct light to the observer’s eyes.

GIA's definition of brightness is pretty close too:

The appearance or extent of internal and external reflections of "White" light seen in a polished diamond when viewed face-up.

From a thread started by the man the myth, RockDiamond. [URL='https://www.pricescope.com/community/threads/discussion-of-green-in-an-aset-image.150479/']https://www.pricescope.com/community/threads/discussion-of-green-in-an-aset-image.150479/[/URL][/quote]

Thanks Teobld. Yes, all the issues being discussed here with RD were covered back in 2010 with him.
Perhaps your understanding is abit more advanced now David - you could go and read that thread and then
1. ask more informed questions
2. make more informed statements
3. and above all, answer Sergey's pending question - what is your definition of FIRE?

 

[Garry H (Cut Nut)]

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).

From the various articles we have published and will soon be published:

Some experts, believe that brilliance is the same in both a stationary and a moving diamond, but that a static diamond is simply easier to study. Others argue that a moving diamond shows only scintillation and fire, i.e. we can see either brilliance or scintillation – but not both at once. As our goal is to create metrics for perception of these phenomena we began by studying what brilliance actually is; we concluded that both stereoscopic sight and motion are vital for the perception of strong brilliance. Stereoscopic sight creates Binocular Rivalry - when each eye ‘sees’ a different intensity at the same spot. Diamond photos show no brilliance, a mono movie and a still stereo image show a little, but a stereo or 3D diamond movie has real brilliance.

 

[Texas Leaguer]

Garry,
This is exciting stuff. Looking forward to reading the articles.

Here's a basic terminology question: How does the term "brightness" relate to the approach you are taking to describe light performance? Is it the same as "brilliance" in your parlance or is there a distinction,( e.g. brightness + dynamic contrast).

You say in the post above "Some experts believe that brilliance is the same in both a stationary and a moving diamond, but that a static diamond is simply easier to study. Others argue that a moving diamond shows only scintillation and fire, i.e.we can see either brilliance or scintillation– but not both at once."

I understand "scintillation" to be dependent on motion. Therefore it is the only aspect that cannot be observed in a static view. Meanwhile, brightness and contrast (brilliance?) can be observed in static view and in motion. Thus I don't understand the statement that a moving diamond shows only scintillation and fire, since it also shows brilliance.

 

[Karl_K]

Garry,
This is exciting stuff. Looking forward to reading the articles.

Here's a basic terminology question: How does the term "brightness" relate to the approach you are taking to describe light performance? Is it the same as "brilliance" in your parlance or is there a distinction,( e.g. brightness + dynamic contrast).

You say in the post above "Some experts believe that brilliance is the same in both a stationary and a moving diamond, but that a static diamond is simply easier to study. Others argue that a moving diamond shows only scintillation and fire, i.e.we can see either brilliance or scintillation– but not both at once."

I understand "scintillation" to be dependent on motion. Therefore it is the only aspect that cannot be observed in a static view. Meanwhile, brightness and contrast (brilliance?) can be observed in static view and in motion. Thus I don't understand the statement that a moving diamond shows only scintillation and fire, since it also shows brilliance.

That is one thing that really bugs me about diamond research is everyone wants to define terms in different ways to fit their model.
That makes communication harder and creates confusion.

 

[Serg]

Garry,
This is exciting stuff. Looking forward to reading the articles.

Here's a basic terminology question: How does the term "brightness" relate to the approach you are taking to describe light performance? Is it the same as "brilliance" in your parlance or is there a distinction,( e.g. brightness + dynamic contrast).

You say in the post above "Some experts believe that brilliance is the same in both a stationary and a moving diamond, but that a static diamond is simply easier to study. Others argue that a moving diamond shows only scintillation and fire, i.e.we can see either brilliance or scintillation– but not both at once."

I understand "scintillation" to be dependent on motion. Therefore it is the only aspect that cannot be observed in a static view. Meanwhile, brightness and contrast (brilliance?) can be observed in static view and in motion. Thus I don't understand the statement that a moving diamond shows only scintillation and fire, since it also shows brilliance.

Bryan,

we distinguish between Brightness, Subjective Brightness and Brilliancy.
Brilliancy is not just Brightness + Spatial Contrast.
3 rivalry are important to create good Brilliancy: Stereo rivalry, Temporal Rivalry, Spatial Rivalry.

 

[Rockdiamond]

Garry,
This is exciting stuff. Looking forward to reading the articles.

Here's a basic terminology question: How does the term "brightness" relate to the approach you are taking to describe light performance? Is it the same as "brilliance" in your parlance or is there a distinction,( e.g. brightness + dynamic contrast).

You say in the post above "Some experts believe that brilliance is the same in both a stationary and a moving diamond, but that a static diamond is simply easier to study. Others argue that a moving diamond shows only scintillation and fire, i.e.we can see either brilliance or scintillation– but not both at once."

I understand "scintillation" to be dependent on motion. Therefore it is the only aspect that cannot be observed in a static view. Meanwhile, brightness and contrast (brilliance?) can be observed in static view and in motion. Thus I don't understand the statement that a moving diamond shows only scintillation and fire, since it also shows brilliance.

That is one thing that really bugs me about diamond research is everyone wants to define terms in different ways to fit their model.
That makes communication harder and creates confusion.

This is an amazing point Karl- and central to the discussion. Using terms molded to fit a given model is a problem when context is not provided. I see it as, in part, practical considerations.
A lab that does scientific research for publication, and or commercial use is going to define things in a manner that's descriptive, yet supports their conclusions.
Take this line - right out of a paper Bryan referred me to on the subject of fire:

"The phenomenon of fire is one of the most appealing effects in transparent gemstones"

I could not copy and past- to see the entire paragraph here' the link Section 5.4
http://www.agslab.com/spie/spie_lo_res.pdf

It goes on to clarify the term "fire" as they apply it to the scientific observed phenomena. ( a very cool aspect of diamonds, I agree)
I have no qualms whatsoever with the observation- and I totally agree that understanding what the terms mean in the context of this scientific study are important- Still. I find conclusions like the sentence I quoted to be entirely unscientific.
At the very least such information could be conveyed in a statistical manner to both back up the statement and put it in context.
For example, 75% of observers polled impartially preferred a fiery gemstone to one which exhibited less fire yet more scintillation.

We all know that any poll on a subjective matter- human taste - is going to produce mixed results.

teobdl- thank you so much for finding the older thread.
It was informative to the discussion here.
The point- that being, how to asess scintillation - that has never yet been fully addressed

 

[Texas Leaguer]

A lab that does scientific research for publication, and or commercial use is going to define things in a manner that's descriptive, yet supports their conclusions.
Take this line - right out of a paper Bryan referred me to on the subject of fire:

"The phenomenon of fire is one of the most appealing effects in transparent gemstones"

I could not copy and past- to see the entire paragraph here' the link Section 5.4
http://www.agslab.com/spie/spie_lo_res.pdf

It goes on to clarify the term "fire" as they apply it to the scientific observed phenomena. ( a very cool aspect of diamonds, I agree)
I have no qualms whatsoever with the observation- and I totally agree that understanding what the terms mean in the context of this scientific study are important- Still. I find conclusions like the sentence I quoted to be entirely unscientific.
At the very least such information could be conveyed in a statistical manner to both back up the statement and put it in context.
For example, 75% of observers polled impartially preferred a fiery gemstone to one which exhibited less fire yet more scintillation.

We all know that any poll on a subjective matter- human taste - is going to produce mixed results.

teobdl- thank you so much for finding the older thread.
It was informative to the discussion here.
The point- that being, how to asess scintillation - that has never yet been fully addressed

David,
If you want the discussion to be constructive you need to stop pouncing on any subjective word or sentence in any statement, report or study to proclaim it “unscientific”.

It’s ludicrous to pull that line out of the AGS study to somehow discredit the findings, and then to turn around and say that instead of stating a rather obvious fact that they should have stated it in percentages of a poll. The poll itself would have to contain questions of a subjective nature (which do you prefer A,B,or C). It amounts to a disingenuous argument.

It appears from your posts in many past threads that you have been attempting to pull people into this endless loop with you for years. It’s really not fruitful. Certain assumptions are perfectly legitimate and necessary in scientific research. If you wanted to find out why the sky is blue, it might be reasonably assumed that most people see it as blue.

It is a pretty well established fact that people find diamonds beautiful. There are various aspects to that beauty. The whole purpose of researching light performance is to understand what the components of beauty are, how they might be quantified, how they relate to one another and to human sensory systems, and what the implications are for cut craftsmanship. To the extent that consumers understand these things they can make better purchasing decisions. To the extent diamond cutters can better understand these things, they can cut more beautiful diamonds (yes I said beautiful). And to the extent we merchants understand it better, we can offer better products and guidance to our customers.

 

[Rockdiamond]

Hi Bryan,
I did not mean to discredit any study- however is there no possibility to discuss- and yes, possibly question the findings or presentation without being accused of trashing it?
Would you say all gemological experts agree with AGS finding or methodology?
We both know the answer is, of course not.
If you're implying that I find this subject fascinating, and can get value out of renewed discussion of it, yes. This will also help consumer readers- many of whom won't go back to four year old discussions.
We discussed green in ASET four years ago, and I've come a long way in my understanding of the devices and technology, and vocabulary. We are not simply re-hashing the discussion of four years ago- new concepts and issues have been raised.
My point about the issue of scintillation not being a settled matter among gemological experts is a fact.
Even as a seller, I'd think you would want the possibility of a workable methodology to be able to cater to folks looking for well cut "crushed ice"
If it's going to be ASET, and the chart published earlier in the thread is not helpful.
ETA- and the chart could easily be a lot more useful simply by having better labels for the different examples

 

[Texas Leaguer]

Hi Bryan,
I did not mean to discredit any study- however is there no possibility to discuss- and yes, possibly question the findings or presentation without being accused of trashing it?
Would you say all gemological experts agree with AGS finding or methodology?
We both know the answer is, of course not.
If you're implying that I find this subject fascinating, and can get value out of renewed discussion of it, yes. This will also help consumer readers- many of whom won't go back to four year old discussions.
We discussed green in ASET four years ago, and I've come a long way in my understanding of the devices and technology, and vocabulary. We are not simply re-hashing the discussion of four years ago- new concepts and issues have been raised.
My point about the issue of scintillation not being a settled matter among gemological experts is a fact.
Even as a seller, I'd think you would want the possibility of a workable methodology to be able to cater to folks looking for well cut "crushed ice"
If it's going to be ASET, and the chart published earlier in the thread is not helpful.
ETA- and the chart could easily be a lot more useful simply by having better labels for the different examples

David,
It seems to me that you throw alot of "stuff" out to see what sticks and who bites. Some of it reasonable, some hard to decipher, some of it contradictory, some of it nonsense. I don't really understand what you are trying to accomplish. If you think this makes for fruitful discussion, I disagree. I'm sure you have alot to offer, but to me its getting lost in the chaos. I prefer to no longer be dragged in.

 

[Karl_K]

It is a pretty well established fact that people find diamonds beautiful. There are various aspects to that beauty. The whole purpose of researching light performance is to understand what the components of beauty are, how they might be quantified, how they relate to one another and to human sensory systems, and what the implications are for cut craftsmanship. To the extent that consumers understand these things they can make better purchasing decisions. To the extent diamond cutters can better understand these things, they can cut more beautiful diamonds (yes I said beautiful). And to the extent we merchants understand it better, we can offer better products and guidance to our customers.

Well said! I would add.
And diamond designers can create better designs and be more sure of a design before it is actually cut.
There is a lot of "that looks right" that goes into diamond design today.
Replacing at least some of that with scientific data improves how diamonds are designed and reduces the risks of cutting expensive rough into a new design.
I think "that looks right" will always be a part of it however.