Which is more important? Fire or brightness?

[Paul-Antwerp]

Since you choose to ignore my first remark, Garry, please can you answer the following question. It should be no problem for you, with all the computing power at your disposal.

Could you tell me of the rays of light exiting a diamond, on average, what percentage of these ray are actually white? I am curious.

Live long,

 

[Garry H (Cut Nut)]

Since you choose to ignore my first remark, Garry, please can you answer the following question. It should be no problem for you, with all the computing power at your disposal.

Could you tell me of the rays of light exiting a diamond, on average, what percentage of these ray are actually white? I am curious.

Live long,

Hi Paul,
I am not ignoring you - I needed some time to get some videos uploaded to help.
But your last question - I am sure Sergey will tell you that it depends on the source of the rays. If they are from big light sources then there is little or no coloured flashes.
If they are from a small number of very small sources, then the diamond can show a lot of fire (with dark background like when we look at a well cut diamond in direct sunlight).
These two videos might help explain a lot.

This one shows good fire -it is a small number of LED's in ViBox http://www.youtube.com/watch?v=L35_XHAHPrs
This one shows brightness and dark zones rather well. It can help with an idea of scintillation (whatever that is) but not really very useful for brilliance http://www.youtube.com/watch?v=UBFBkYLesV8

If you are not playing them in 1080 HD - then give your computer a break until they fully download and choose HD please.

 

[jmarshall]

it sure would be groovy to have an HCA tool for Emerald and Asscher cuts.

That will never happen, you can have 2 step cut diamonds with the exact same angles and ones a total woofer and the other rocks.
With a round the design locks the facets into specific locations, how tightly depends on the cutting quality. But overall there is little room for variation other than lgf%/lgh%.
This is not the case with step cuts. The facets can be in many different locations.

Sorry folks, Karl is right. Rounds and maybe square Princess are the only cuts that HCA can really extend to.

I would be VERY curious to plug the dimensions of the princess I just bought into the calculator to see what it said just for shiggles. I think the ability to do this would be very nice.

 

[Paul-Antwerp]

Since you choose to ignore my first remark, Garry, please can you answer the following question. It should be no problem for you, with all the computing power at your disposal.

Could you tell me of the rays of light exiting a diamond, on average, what percentage of these ray are actually white? I am curious.

Live long,

Hi Paul,
I am not ignoring you - I needed some time to get some videos uploaded to help.
But your last question - I am sure Sergey will tell you that it depends on the source of the rays. If they are from big light sources then there is little or no coloured flashes.
If they are from a small number of very small sources, then the diamond can show a lot of fire (with dark background like when we look at a well cut diamond in direct sunlight).
These two videos might help explain a lot.

This one shows good fire -it is a small number of LED's in ViBox http://www.youtube.com/watch?v=L35_XHAHPrs
This one shows brightness and dark zones rather well. It can help with an idea of scintillation (whatever that is) but not really very useful for brilliance http://www.youtube.com/watch?v=UBFBkYLesV8

If you are not playing them in 1080 HD - then give your computer a break until they fully download and choose HD please.

Cool, Garry,

So, if for the same diamond, the difference between brightness and fire depends mostly on the size of the light source,
- fire is not the enemy of brightness?
- adjusting the HCA in order to give more weight to fire has no meaning?

Live long,

 

[chrono]

Not a simple answer for this at all. Brightness is definitely important and so is fire but fire doesn't "show up" all the time. Although I love fire, I would not want it at the expense of brightness because there are far more light conditions that favour brightness than fire. Where is that tipping point? I don't know but being able to see and compare various combination of levels will make it clearer and hopefully easier to decide that perfect point for me.

 

[Paul-Antwerp]

Let me summarize my position about brightness and fire:

- Whether light hits your eyes is a probability determined by the diamond,
- Whether the light hitting your eye is perceived as being white (brightness) or colored (fire) depends mostly on the light source and the observer (pupil size, position of the eyes, translation by the brain, ...).
- Cut (thus basically the diamond) can change the likelihood of observing fire, but that is beyond the level of detail the HCA uses.

Live long,

 

[Serg]

Cut and Size are main reasons of the difference in Fire between any two diamonds.
Two diamonds may have quite different Fire in same light environment. ( for easy examples: Princess and Round Cut, Crushed Ice Cuts and Round cut, 0.1 Ct Round and 3ct Round, ..)

 

[backwardsandinheels]

Thanks for videos, that helped a bit. I value both. I'd have to defer to brilliance 60/40 over fire. Do they have to be mutually exclusive?

 

[teobdl]

Let me summarize my position about brightness and fire:

- Whether light hits your eyes is a probability determined by the diamond,
- Whether the light hitting your eye is perceived as being white (brightness) or colored (fire) depends mostly on the light source and the observer (pupil size, position of the eyes, translation by the brain, ...).
- Cut (thus basically the diamond) can change the likelihood of observing fire, but that is beyond the level of detail the HCA uses.

Live long,

THIS.

Dispersion (or "fire") is not a function of angles (read: cut). It's a function of the materials (read: composition of a diamond). White light contains different frequencies, and the speed of light in matter depends on frequency. The dispersion of light occurs because each color (frequency) travels at slightly different speeds through the diamond.
Cut will not change the material, but maybe the amount of nitrogen or other elements in a diamond would affect the material enough to impact amount of dispersion.

I've been very confused by the claim that cut will affect fire. Maybe I'm missing something, but from a electromagnetic/material physics perspective, it doesn't make sense to me.

If someone can point me to a resource that demonstrates using physics how cut can affect dispersion, I'll be happy to change my tune. I should say that I'm not a physicist by training (medicine).
That said, in my mind, the only conceivable way that cut might increase dispersion (in certain lighting) would be by maximizing the internally reflected path and minimizing light loss out of lower facets. In other words, increasing virtual facets and maintaining brightness. I believe that this is already a chief goal in smart diamond cutters, like Paul Slegars and Brian Gavin.

Edit to add: AND, if virtual facets play are the principal driver of fire, then facet alignment will play as big a role, if not bigger role, than the HCA inputs.

 

[Garry H (Cut Nut)]

Thanks for videos, that helped a bit. I value both. I'd have to defer to brilliance 60/40 over fire. Do they have to be mutually exclusive?

There is a part of mutual exclusivity.

Paul alluded to this (I think he had it the wrong way around).

When you see a firey flash from one facet with one eye, and a bright white light area from the same virtual facet or region with the other eye, then the brain computes bright colorless. So in that sense brilliance can be the enemy of fire.
If you see a bright coloured flash with one eye and a dark or dull region with the other, the flash will be seen and registered as strong. This is further complicated because many coloured flashes start at red or blue and pass through white then turn blue or red (respectively).

And yes - steep crown shallow pavilion diamonds have more fire potential and shallow crown deeper pavilion diamonds have more brightness / brilliance potential.

 

[Serg]

reispersion (or "fire") is not a function of angles (read: cut). It's a function of the materials (read: composition of a diamond).


Dispersion is not Fire. Material Dispersion( difference in Refractive indexes ) is just one factor which is necessary to create Fire.

Diamond parallel plate has same dispersion as round diamond. But parallel plate has not same Fire as round cut.

Angular Dispersion for prism depends from prism angle( cut)

 

[Garry H (Cut Nut)]

Since you choose to ignore my first remark, Garry, please can you answer the following question. It should be no problem for you, with all the computing power at your disposal.

Could you tell me of the rays of light exiting a diamond, on average, what percentage of these ray are actually white? I am curious.

Live long,

Hi Paul,
I am not ignoring you - I needed some time to get some videos uploaded to help.
But your last question - I am sure Sergey will tell you that it depends on the source of the rays. If they are from big light sources then there is little or no coloured flashes.
If they are from a small number of very small sources, then the diamond can show a lot of fire (with dark background like when we look at a well cut diamond in direct sunlight).
These two videos might help explain a lot.

This one shows good fire -it is a small number of LED's in ViBox http://www.youtube.com/watch?v=L35_XHAHPrs
This one shows brightness and dark zones rather well. It can help with an idea of scintillation (whatever that is) but not really very useful for brilliance http://www.youtube.com/watch?v=UBFBkYLesV8

If you are not playing them in 1080 HD - then give your computer a break until they fully download and choose HD please.

Cool, Garry,

So, if for the same diamond, the difference between brightness and fire depends mostly on the size of the light source,
- fire is not the enemy of brightness? PAUL BRIGHTNESS IS THE ENEMY OF FIRE
- adjusting the HCA in order to give more weight to fire has no meaning?

Live long,

- fire is not the enemy of brightness? PAUL BRIGHTNESS IS THE ENEMY OF FIRE

 

[arkieb1]

I bought a diamond with HCA under 1 and with a good idealscope image. It was bright and threw lots of fire under the sun. However, it seriously lacked scintillation, it did not sparkle in almost all lightings. At a jeweler's store, it faced up whiter than a G (GIA) but it looked very flat while the G sparkled. I returned it.

If I can refer to another thread, the op has the same problem: [URL='https://www.pricescope.com/community/threads/not-as-sparkle-as-what-the-number-reflects.190162/']https://www.pricescope.com/community/threads/not-as-sparkle-as-what-the-number-reflects.190162/[/URL]

Someone told me something like this: I buy diamond for its fire and sparkle. If I want a white diamond, I'd buy a white sapphire.

I know your questions is between fire or brightness. Fire is more important to me. And maybe you can do something about scintillation too

And once again here was the point I was making above, you need fire, brilliance AND scintillation to really judge overall particularly in old cuts.... plus if you are doing an advanced guide for people what about types of things like graining, internal graining, surface graining, explaining how sometimes clouds not seen can make a diamond that scores perfectly on your tools still look like a pooper..... or a perfectly cut H & A stone with an etch channel or a chip in it. If it was me I would have two guides people could look at one that does your basic calculations and another with a big chart of what all the terms on a diamond certificate could possibly mean and how each one may or may not detract from the overall appearance of the stone in question.

 

[Garry H (Cut Nut)]

I bought a diamond with HCA under 1 and with a good idealscope image. It was bright and threw lots of fire under the sun. However, it seriously lacked scintillation, it did not sparkle in almost all lightings. At a jeweler's store, it faced up whiter than a G (GIA) but it looked very flat while the G sparkled. I returned it.

If I can refer to another thread, the op has the same problem: [URL='https://www.pricescope.com/community/threads/not-as-sparkle-as-what-the-number-reflects.190162/']https://www.pricescope.com/community/threads/not-as-sparkle-as-what-the-number-reflects.190162/[/URL]

Someone told me something like this: I buy diamond for its fire and sparkle. If I want a white diamond, I'd buy a white sapphire.

I know your questions is between fire or brightness. Fire is more important to me. And maybe you can do something about scintillation too

And once again here was the point I was making above, you need fire, brilliance AND scintillation to really judge overall particularly in old cuts.... plus if you are doing an advanced guide for people what about types of things like graining, internal graining, surface graining, explaining how sometimes clouds not seen can make a diamond that scores perfectly on your tools still look like a pooper..... or a perfectly cut H & A stone with an etch channel or a chip in it. If it was me I would have two guides people could look at one that does your basic calculations and another with a big chart of what all the terms on a diamond certificate could possibly mean and how each one may or may not detract from the overall appearance of the stone in question.

Well put Arkieb1. The group I work with are developing selection tools. So far all the tools we have to hand are rejection tools to narrow the range of potential diamonds. HCA is a rejection tool.
The survey that is pinned at the top of the forums shows a selection based tool.

 

[Paul-Antwerp]

Since you choose to ignore my first remark, Garry, please can you answer the following question. It should be no problem for you, with all the computing power at your disposal.

Could you tell me of the rays of light exiting a diamond, on average, what percentage of these ray are actually white? I am curious.

Live long,

Hi Paul,
I am not ignoring you - I needed some time to get some videos uploaded to help.
But your last question - I am sure Sergey will tell you that it depends on the source of the rays. If they are from big light sources then there is little or no coloured flashes.
If they are from a small number of very small sources, then the diamond can show a lot of fire (with dark background like when we look at a well cut diamond in direct sunlight).
These two videos might help explain a lot.

This one shows good fire -it is a small number of LED's in ViBox http://www.youtube.com/watch?v=L35_XHAHPrs
This one shows brightness and dark zones rather well. It can help with an idea of scintillation (whatever that is) but not really very useful for brilliance http://www.youtube.com/watch?v=UBFBkYLesV8

If you are not playing them in 1080 HD - then give your computer a break until they fully download and choose HD please.

Cool, Garry,

So, if for the same diamond, the difference between brightness and fire depends mostly on the size of the light source,
- fire is not the enemy of brightness? PAUL BRIGHTNESS IS THE ENEMY OF FIRE
- adjusting the HCA in order to give more weight to fire has no meaning?

Live long,

- fire is not the enemy of brightness? PAUL BRIGHTNESS IS THE ENEMY OF FIRE

Why the shout? It does not explain a thing.

Again, if the same light path and the same diamond, depending on the size of the light source, in one instance produce brightness, in the other fire, it means they are partners not enemies. Shouting is not going to change that logic.

Furthermore, if in the same circumstances, one observer will see brightness and the other fire, again, it means they are partners, not enemies.

It is easy to find exceptional situations, where the above general rule does not apply, but you finding some yellow tomatoes does not change the general rule that tomatoes are red.

Live long,

 

[teobdl]

reispersion (or "fire") is not a function of angles (read: cut). It's a function of the materials (read: composition of a diamond).


Dispersion is not Fire. Material Dispersion( difference in Refractive indexes ) is just one factor which is necessary to create Fire.
Without dispersion, there will be no perception of fire. Without light reflected back at the viewer, there will be no perception of fire. If you are defining fire as something other than "the perception of spectral colors that result from dispersed light hitting a viewer's eyes," then please redefine it.

Diamond parallel plate has same dispersion as round diamond. But parallel plate has not same Fire as round cut.
I think your point is that the size and distribution of colors will be different. But this is like saying an AVR will have different fire than a modern round brilliant. I agree that cut changes the "flavor" of the fire. But as long as light passes through a diamond and hits the viewer, there will still be fire, and that color will turn white if you make the light source bigger.

Angular Dispersion for prism depends from prism angle( cut)
To clarify that statement, I think you mean angular refraction from dispersed light depends on angle (cut). This is true of any ray of light. It is also true that the angle at which dispersed light encounters a facet will either broaden OR narrow the spread of the dispersed light when it is refracted out. If the spread of the dispersed light is broader, then there will be a higher probability that the viewer sees and perceives a spectral color. But please keep in mind that this is contingent on dozens of factors, including the location and brightness of the light source(s), location and distance of the viewer, distance between the eyes, whether the viewer is square to the diamond, etc. The only factor the diamond can somewhat control is whether light that enters is directed back to the eyes. This is cut.

See my responses to Serg above.

And yes - steep crown shallow pavilion diamonds have more fire potential and shallow crown deeper pavilion diamonds have more brightness / brilliance potential.

I'm sure something like OctoNus could model this. But also please move the viewer away from center, then intensify the light source, then dim the light source, then add light sources, then make the viewer closer, then farther, and go through every permutation. This is real life. Is it still the case that shallow pavilion and steep crown have a higher overall probability of creating fire as perceived by the viewer?

If the answer is yes, I will believe the claim.

 

[Garry H (Cut Nut)]

I'm sure something like OctoNus could model this. But also please move the viewer away from center, then intensify the light source, then dim the light source, then add light sources, then make the viewer closer, then farther, and go through every permutation. This is real life. Is it still the case that shallow pavilion and steep crown have a higher overall probability of creating fire as perceived by the viewer?

If the answer is yes, I will believe the claim.

Teobdl did you look at the two videos I posted earlier in this thread?
It is apparent that among the round diamonds there is a big difference in the fire between different cuts.
A human will see this also if they are in the same position as the camera with one eye open.
If, as I can on my 3D screen, I look at diamonds in the same light box, I will see the same differences with both eyes open.
So the cut is making a huge difference to the fire that can be seen.
We can also model this in DiamCalc.
You can count the flashes of fire and their duration in the movies. You can replicate this with HDR digital copies of the same lighting in DiamCalc.
You can even make an estimate of the sizes of flashes that are too small to see.
But it is not a metric because no one can say if 2 short flashes = one 2x as long. Or are 2 small flashes as good as one 2x as big.
We hope to be able to make an answer for that one day.

 

[Garry H (Cut Nut)]

Since you choose to ignore my first remark, Garry, please can you answer the following question. It should be no problem for you, with all the computing power at your disposal.

Could you tell me of the rays of light exiting a diamond, on average, what percentage of these ray are actually white? I am curious.

Live long,

Paul you seem to be rather aggressive on this topic. Not sure why?

All or most of the rays leaving a diamond are potentially colored if the aperture they are entering is very very small. In our case we have two apertures - two pupils. They change diameter - small if its bright light and large if its dark. Also we have two types of light detectors - rods and cones, inside our eyes, and they send different info to the brain. So the answer is not a simple answer because, as I have said, the amount of colored light leaving a diamond also depends on the source (small = lots, large = little). So the fire that we can see depends on many factors.
I would like to be able to give a simple answer to your question, but it is impossible.
If your eyes are closer to the diamond you will see more white light than if you are a bit further away - but if you are too far away you will only resolve and separate out to identify the color coming from larger facets. I see more color with my specs off because the flashes get blurred and bigger than with my specs on.
There may be more variables from us than there is from the diamond itself!

Imagine if we can understand that really well and help people buy the type of diamond that best suits them and their likely wearing environment!
Maybe in 10 years time?

 

[Paul-Antwerp]

Since you choose to ignore my first remark, Garry, please can you answer the following question. It should be no problem for you, with all the computing power at your disposal.

Could you tell me of the rays of light exiting a diamond, on average, what percentage of these ray are actually white? I am curious.

Live long,

Paul you seem to be rather aggressive on this topic. Not sure why?

All or most of the rays leaving a diamond are potentially colored if the aperture they are entering is very very small. In our case we have two apertures - two pupils. They change diameter - small if its bright light and large if its dark. Also we have two types of light detectors - rods and cones, inside our eyes, and they send different info to the brain. So the answer is not a simple answer because, as I have said, the amount of colored light leaving a diamond also depends on the source (small = lots, large = little). So the fire that we can see depends on many factors.
I would like to be able to give a simple answer to your question, but it is impossible.
If your eyes are closer to the diamond you will see more white light than if you are a bit further away - but if you are too far away you will only resolve and separate out to identify the color coming from larger facets. I see more color with my specs off because the flashes get blurred and bigger than with my specs on.
There may be more variables from us than there is from the diamond itself!

Imagine if we can understand that really well and help people buy the type of diamond that best suits them and their likely wearing environment!
Maybe in 10 years time?

I am not at all aggressive, Garry, I just want absolute clarity.

In this case, you are not answering my question. I asked about the light rays leaving the diamond, not how they are perceived by an observer at a variable distance.

Live long,

 

[Garry H (Cut Nut)]

Paul what does it mean.
Change the viewer to 15 different analysis programs and you have 15 different results.
Do you weight the results to face up?
do you want all the light?
the colored light leaving the pavilion above and below the girdle horizon?

 

[Garry H (Cut Nut)]

At an infinite distance all light leaving the diamond is colored (edited to say that the light that enters perpendicular to the surface and exits perpendicular is not refracted and no dispersion will occur)

 

[Paul-Antwerp]

At an infinite distance all light leaving the diamond is colored (edited to say that the light that enters perpendicular to the surface and exits perpendicular is not refracted and no dispersion will occur)

I guess that you agree that the chance of light both entering and exiting perpendicular to the diamond's surface is extremely low.

With that said, for the same diamond, the observation of either fire or brightness depends on the light source and the observer. Correct?

Live long,

 

[delight]

Sorry to butt-in in the middle of the discussion. I am curious to know what is the software that Garry used in demonstrating the light rays leaving the diamond?

 

[Garry H (Cut Nut)]

Sorry to butt-in in the middle of the discussion. I am curious to know what is the software that Garry used in demonstrating the light rays leaving the diamond?

DiamCalc. It is Serg's software that he developed and is a key component in diamond cut quality and cut design solutions.
(Disclosure - I sell it)

 

[Garry H (Cut Nut)]

At an infinite distance all light leaving the diamond is colored (edited to say that the light that enters perpendicular to the surface and exits perpendicular is not refracted and no dispersion will occur)

1. I guess that you agree that the chance of light both entering and exiting perpendicular to the diamond's surface is extremely low.

2. With that said, for the same diamond, the observation of either fire or brightness depends on the light source and the observer. Correct?

Live long,

1. For light entering perpendicular the chances are greater than for at an oblique angle (more is reflected at an oblique angle and never enters). Having entered the diamond, a greater proportion of light will exit perpendicular than at an oblique angle (light may only exit for a small number of degrees, about 49 out of 180).
So no.

2. For the same diamond, yes.

I do not understand any relevance of this to HCA, or fire vs brightness / brilliance Paul?

 

[Paul-Antwerp]

I am sorry, Garry, but I am asking questions to you. In that scenario, relevance is judged by the judge, not by the person testifying.

I do not really get your first answer. I think that you are saying that when a ray enters the stone perpendicular to the surface, there is a higher chance of entering than when it hits at an angle. Granted, but that is not my question, since I guess that the number of rays hitting the surface at an angle is a multi-fold of those 'accidentally' hitting perpendicular to the surface.

About light exiting, you are answering in the same way to another question. Same reasoning here.

Therefore, please clarify, since your 'no' does not satisfy.

Thank you, for your answer to the second question. That means, that for the same diamond, it is external aspects (the light source and the observer) who determine whether a light-ray is bright or fiery. For the same observer, the same diamond can be extremely bright in one light-environment, extremely fiery in another light-environment. It shows that brightness and fire go hand-in-hand.

They are not the same, and cutting at micro-level can increase the likelihood of fire being observed, but the above makes it abundantly clear that they do go hand-in-hand, and are not enemies.

Live long,

 

[Serg]

reispersion (or "fire") is not a function of angles (read: cut). It's a function of the materials (read: composition of a diamond).


Dispersion is not Fire. Material Dispersion( difference in Refractive indexes ) is just one factor which is necessary to create Fire.
Without dispersion, there will be no perception of fire. Without light reflected back at the viewer, there will be no perception of fire. If you are defining fire as something other than "the perception of spectral colors that result from dispersed light hitting a viewer's eyes," then please redefine it.


Fire is absent also without diamond .
Fire is absent without color sensitive observers.

But diamond is not Fire, observer is not fire, light is not fire, dispersion is not fire.




Diamond parallel plate has same dispersion as round diamond. But parallel plate has not same Fire as round cut.
I think your point is that the size and distribution of colors will be different. But this is like saying an AVR will have different fire than a modern round brilliant. I agree that cut changes the "flavor" of the fire. But as long as light passes through a diamond and hits the viewer, there will still be fire, and that color will turn white if you make the light source bigger.

Angular Dispersion for prism depends from prism angle( cut)
To clarify that statement, I think you mean angular refraction from dispersed light depends on angle (cut). This is true of any ray of light. It is also true that the angle at which dispersed light encounters a facet will either broaden OR narrow the spread of the dispersed light when it is refracted out. If the spread of the dispersed light is broader, then there will be a higher probability that the viewer sees and perceives a spectral color. But please keep in mind that this is contingent on dozens of factors, including the location and brightness of the light source(s), location and distance of the viewer, distance between the eyes, whether the viewer is square to the diamond, etc. The only factor the diamond can somewhat control is whether light that enters is directed back to the eyes. This is cut.

Do you select life style for your diamond , Or a diamond for your life style?


There are 2 diamonds and 2 lights environments that first diamond has more more than second diamond in first light environments , and second diamond has more fire then first diamond in second light environment .
But usually if first diamond has much more fire in any real consumer light environment then this diamond also has much more fire in any other real consumer light environment .

If you want discuss about cut influence for fire you have to fix all other subjects and compare diamonds in same conditions. Otherwise you just spoil time.



See my responses to Serg above.

And yes - steep crown shallow pavilion diamonds have more fire potential and shallow crown deeper pavilion diamonds have more brightness / brilliance potential.

I'm sure something like OctoNus could model this. But also please move the viewer away from center, then intensify the light source, then dim the light source, then add light sources, then make the viewer closer, then farther, and go through every permutation. This is real life. Is it still the case that shallow pavilion and steep crown have a higher overall probability of creating fire as perceived by the viewer?

If the answer is yes, I will believe the claim.

I do not need to Believe. You may check it yourself . Just do it and think about that and why you see.
I did it , Garry did. We did tests, we modeled it theoretically . what did you do to check you statements ?

 

[teobdl]

I have not done scientific tests myself. What I have done is apply optical physics to issues being discussed.

If my writing has come across as didactic, it's because I am trying to state my position as clearly as possible so that specific issues within my line of thinking can be addressed if they are incorrect. As a scientist, I want my theoretical understanding of a subject to align with observation. It is frustrating to hear, in essence, "Just trust us." Questioning the validity and scope of studies, observations, and claims is a helpful endeavor.

There are three questions I want to address:

1. Does cut influence fire?
Short answer: Yes.
Long answer: I do not disagree that, in the same lighting conditions, two differently cut diamonds will have different flavors and balance of brightness and fire. But this is not the issue. The issue is that for each diamond in each situation, whether one sees more brightness or more fire depends on conditions other than cut.

2. Does the HCA predict a probability for Fire vs Brightness
Short answer: Yes.
Long answer: Yes, but it is applicable to a very limited set of conditions. For me, this is a major limitation that is not discussed enough. Let me state clearly that this limitation is not Garry's fault--its just the nature of doing science well. He did his controlled experiments. He published his methods. He described the results fantastically, and he even made his results practical for the general public! He did his job. As users of the HCA, we are not doing our job to define and critique the scope of its utility.

So here is what users of the HCA should know: Within each set of proportions, the HCA's predicted probability of fire or brightness assumes a centered, perpendicular position relative to the diamond's table, at a defined distance from the diamond, and with a certain light source.

Everyone who uses the tool as a predicted measure of brightness vs fire should be asking this question: Can the results of that specifically defined experiment be extrapolated to real life situations, most of which do not mimic that defined environment? The modeling was performed with a distance of 16 inches. http://www.diamond-cut.com.au/10_method.htm Even if Garry had backed up 6 inches when doing his experiments, the results of fire and brilliance would be different.
Fire becomes brilliance and brilliance becomes fire depending on the conditions.

3. What is fire?
If someone measuring fire will not define it, or if s/he thinks it it is beyond definition, then this is a serious problem. So serious, in fact, that it invalidates any endeavor of that person to measure it and make a grade of it, qualitative or quantitive. Garry did define it loosely for his experiments, and I have no gripe with him. But it does reflect very poorly on anyone who will not define it.

 

[Serg]

I have not done scientific tests myself. What I have done is apply optical physics to issues being discussed.

If my writing has come across as didactic, it's because I am trying to state my position as clearly as possible so that specific issues within my line of thinking can be addressed if they are incorrect. As a scientist, I want my theoretical understanding of a subject to align with observation. It is frustrating to hear, in essence, "Just trust us." Questioning the validity and scope of studies, observations, and claims is a helpful endeavor.

There are three questions I want to address:

1. Does cut influence fire?
Short answer: Yes.
Long answer: I do not disagree that, in the same lighting conditions, two differently cut diamonds will have different flavors and balance of brightness and fire. But this is not the issue. The issue is that for each diamond in each situation, whether one sees more brightness or more fire depends on conditions other than cut.

2. Does the HCA predict a probability for Fire vs Brightness
Short answer: Yes.
Long answer: Yes, but it is applicable to a very limited set of conditions. For me, this is a major limitation that is not discussed enough. Let me state clearly that this limitation is not Garry's fault--its just the nature of doing science well. He did his controlled experiments. He published his methods. He described the results fantastically, and he even made his results practical for the general public! He did his job. As users of the HCA, we are not doing our job to define and critique the scope of its utility.

So here is what users of the HCA should know: Within each set of proportions, the HCA's predicted probability of fire or brightness assumes a centered, perpendicular position relative to the diamond's table, at a defined distance from the diamond, and with a certain light source.

Everyone who uses the tool as a predicted measure of brightness vs fire should be asking this question: Can the results of that specifically defined experiment be extrapolated to real life situations, most of which do not mimic that defined environment? The modeling was performed with a distance of 16 inches. http://www.diamond-cut.com.au/10_method.htm Even if Garry had backed up 6 inches when doing his experiments, the results of fire and brilliance would be different.
Fire becomes brilliance and brilliance becomes fire depending on the conditions.

3. What is fire?
If someone measuring fire will not define it, or if s/he thinks it it is beyond definition, then this is a serious problem. So serious, in fact, that it invalidates any endeavor of that person to measure it and make a grade of it, qualitative or quantitive. Garry did define it loosely for his experiments, and I have no gripe with him. But it does reflect very poorly on anyone who will not define it.

if you need our Fire, Brilliancy definition please check

by Serg » 05 Jul 2013 16:45
[URL='https://www.pricescope.com/forum/post3477695.html#p3477695']https://www.pricescope.com/forum/post3477695.html#p3477695[/URL]

 

[Paul-Antwerp]

Therefore, once again, with almost all light coming out of a diamond being dispersed (do correct me if I am wrong , and whether it is observed as brilliance or fire depending on the light source and the observer:

- Brightness as a measure of light return is the total of light exiting observed, thus fire and brilliance totaled (with the distinction being a factor of the light source and the observer),
- the same diamond's calculation of it being leaning more towards brightness or fire is thus a non-issue, since the observation of brightness or fire depends upon the light source and the observer.

With the above being said, my point is that the distinction between brightness and fire in the HCA is a non-issue, the basics of the HCA being too broad to make any difference at that level.

However, at the level of micro-cutting (so to speak, a level of detail the HCA in its broadness does not cover), one can increase the likelihood of observing fire in an overall bright diamond, far above the level of fire-observation in a less-bright diamond.

Live long,