Which is more important? Fire or brightness?

[Garry H (Cut Nut)]

So Paul you believe there is no difference in the visible fire or brilliance crom different cuts and therefore I should not try to assist diamond shoppers.
I give up answering this line of your reasoning.

Sent from my GT-I9305T using PriceScope mobile app

 

[Paul-Antwerp]

Running from the argument is easy, Garry.

You are saying yourself that practically all light exiting is dispersed.
You are saying yourself that the observation of fire is mostly determined by the variables of the light source and the observer.
You are saying yourself that the HCA is a rejection-tool only, in other words a macro-assessment of diamonds.

So, if you want to give up, understand that you are giving up on your own words.

Live long,

 

[oldminer]

With the increasing acceptance of less than purely colorless diamonds, it is also becoming a reality that less purely white light comes out of a diamond as most would be tinted light close to the body color of the diamond. How can you separate "fire" from light that is colored, but body color of the diamond? The variables are simply too great to be worth the computational effort. All faceted diamonds create some degree of fire and a customer should select a diamond they visually prefer. If one wants added dispersion, then get the treatment on the pavilion and have vastly more noticeable fire with no loss of any other attribute.

A diamond with fire levels well above the norm looks like an old diamond substitute, strontium titanate, to me, but to each their own.

 

[Garry H (Cut Nut)]

Running from the argument is easy, Garry.

You are saying yourself that practically all light exiting is dispersed.
You are saying yourself that the observation of fire is mostly determined by the variables of the light source and the observer.
You are saying yourself that the HCA is a rejection-tool only, in other words a macro-assessment of diamonds.

So, if you want to give up, understand that you are giving up on your own words.

Live long,

I am giving up on your obtuse arguments Paul.
HCA has always and only ever been a rejection tool. Why did you ever think otherwise?
All light except that which enters and leave perpendicular to facets (i.e. thru parallel windows) will be seen to be dispersed at some great distance. But that has no meaning for diamond wearers or those sitting near by.

You totally missed this topic for some reason of your own.

 

[Paul-Antwerp]

Garry, in every reply to me in this topic, you have twisted my words or avoided the actual question. Again here.

I never said that I disagree with you on any of these three statements of yours. In fact, I fully agree with all three of them. But on that basis, I have follow-up questions and remarks, and you apparently prefer to walk away from them.

I do not understand. Is there a problem with an inconvenient truth?

Live long,

 

[teobdl]

For future readers of the thread, a deleted post led me to find Peter Yantzer and the AGS lab's research on these topics; specifically, how cut proportions affect brilliance, fire, and scintillation. It has been the single most helpful article I've ever read on diamond light performance, and it addressed every discussion point of this thread.

http://www.agslab.com/spie/spie_lo_res.pdf

Given that Serg and Garry received acknowledgement at the end of the article, I'm a bit disappointed that we were not directed to this paper in the first place. It has taken a lot of the mystery out of the fuzzy notions about proportions and light performance that get thrown around here.

 

[Serg]

For future readers of the thread, a deleted post led me to find Peter Yantzer and the AGS lab's research on these topics; specifically, how cut proportions affect brilliance, fire, and scintillation. It has been the single most helpful article I've ever read on diamond light performance, and it addressed every discussion point of this thread.

http://www.agslab.com/spie/spie_lo_res.pdf

Given that Serg and Garry received acknowledgement at the end of the article, I'm a bit disappointed that we were not directed to this paper in the first place. It has taken a lot of the mystery out of the fuzzy notions about proportions and light performance that get thrown around here.

Teobl, May You please clarify that helpful for You information you found in this article?
Did you found for example What Brilliancy is? What is Fire? ( What is it, Instead How it come into existence )

 

[Paul-Antwerp]

Here is my summary, and please correct me where I am wrong.

Since the chance of pure white light exiting a diamond is close to zero, basically all light exiting a diamond is dispersed. Whether an observer sees it as brightness or fire depends upon the light source and the observer.

Therefore, at the macro-level, brightness and fire are the same, since it is the same light either being observed as brightness or fire, dependent upon external factors to the diamond. That is why I so vehemently state that brightness is not the enemy of fire. In essence, they are the same.

At a micro-level however, the diamond itself can influence the likelihood of either observing brightness or fire. So, the diamond is a factor of influence, but not independent from light source or observer.

Then, in the same light environment, a diamond may be to most observers either more bright or more fiery. One could then say that it is either bright or fiery, and that brightness is the enemy of fire. Granted, but in another light environment, that same diamond will only be observed as bright.

It is this distinction between macro and micro that this thread is completely missing.

Live long,

 

[Serg]

Is anybody know the Observer and Light source which are create Fire in Cut as parallel plate ?
there are many flat rough .

Micro level, macro level,. , ,

Below certain level we do not see Fire. Cut and/or Observer have to reject significant part of light beam to create Visible( by Human of course) Fire.
is anybody agree to pay for Invisible Fire? I want see as sales person sell Invisible Fire for diamond consumers.

Moreover- to create nice appearance of Fire a Cut has to have dark zones to increase contrast. Same Color flash on dark and bright backgrounds has quite different appearance . ( check for example CIE1997 or modern Hunt books)
Similar for Brilliancy . Subjective brightness and Objective brightness are very different. To increase Subjective brightness cut has to have sone black zone( decrease total light flux from diamond)


"Brilliance is a kind of an illusion, the essence of which is the fact that the subjective contrast of the perceived image of an object dramatically exceeds the actual contrast of the object itself. This illusion may appear when several image segments that substantially differ in brightness fall into a single spatio-temporal domain of perception. In the case when the observed object is a diamond, such segments are usually its virtual facets. Two virtual facets belong to a single spatio-temporal domain if the observer is not able to perceive them as separate ones due to either spatial or temporal constraints of the human vision system.

The cause of brilliance consists in multiple enhancement of the contrast between the dark and light facets, conditioned by the work of the brain. Superposition of a number of contrast enhancement effects brings about paradoxical results inability to describe which by habitual ways forces the brain to generate the phenomenon of brilliance.
While static brightness and contrast are important to take into account in a brilliance metric we believe that without considering motion and stereo it is not possible to develop reliable metric for correct different cuts comparison. According to our observations motion and stereo give main input into Brilliance.
The perception of brilliance remains unaffected by facets reflecting sources whose intensity is by several orders of magnitude higher than the average intensity of all sources involved in the diamond image construction. Facets that reflect such sources have sharply different characteristics for perception by the brain, and the brain separates them from the phenomenon of brilliance to class them into a phenomenon called Scintillation.

"


all above had been write by Barbarian . No " peer reviews"

 

[Paul-Antwerp]

Sergey,

While your smilies above are inappropriate, I agree with you that contrast is going to increase the likelihood of observing fire.

So, please explain to me, after Garry first ignored, then avoided the matter and eventually ran off, how can the HCA with its limited input-variables predict such contrast?

It is what got this thread started, and all statements here (and I agree with almost all of what you and Garry have said) indicate that the HCA cannot give such a prediction.

So, please indulge me, train me, teach me.

Live long,

 

[teobdl]

Serg--
The matrices were very helpful for me pulling out trends of contrast patterning, fire, and dynamism through the various pavilion and crown combinations and at various tilt/illumination environments.
Just to pick one example, it provided proof that high crown angles fan out dispersed light to a greater degree than low crown angles This favors the viewer to see colored light rather than white light. In other words, high crown diamonds are more likely to appear fiery as closer distances to the diamond. I didn't believe you or Garry; now I do because I saw proof of the research.

_______

I think that statements such as "brightness is the enemy of fire" are unhelpful, even unintentionally misleading, to a consumer. It suggests in his/her mind that a diamond will almost always look bright or almost always look fiery. Well, here's something to think about--a diamond that looks very bright to the wearer will likely look every bit as fiery as a "fire-prone" diamond to an observer across the table (say, 3 ft; 100 cm away). I'd bet most people on PriceScope have no idea that this is the case.

One should just state that certain characteristics of this diamond favor seeing colored light more often than bright white light in certain conditions. End of story.

_______

Re: use of the HCA for predicting brightness, fire, and scint: now that I see the fire, brightness, and scintillation trends that the HCA purports to "grade" (I know--bad word, but I can't think of a better description), I think it would be much more helpful to have a few comparison diamonds to say "Your diamond will likely be a little less fiery than Example A, etc".

As far as grading brightness, maybe a more helpful grade would be to use the ASET image of the Tolk. ideal as a benchmark of both brightness AND contrast. As has been stated here, brightness alone has little beauty without dynamic contrast.

 

[Ella]

We are sorry for the interruption folks, but please don't feed the troll! A user who has been banned multiple times from this website from refusing to follow our policies and more importantly being nasty to our members keeps trying to post in this thread.

Please enjoy the conversation and report him instead of quoting his posts if you see him! Thank you for your assistance.

 

[Serg]

Teobl,

Serg--
The matrices were very helpful for me pulling out trends of contrast patterning, fire, and dynamism through the various pavilion and crown combinations and at various tilt/illumination environments.
Just to pick one example, it provided proof that high crown angles fan out dispersed light to a greater degree than low crown angles This favors the viewer to see colored light rather than white light. In other words, high crown diamonds are more likely to appear fiery as closer distances to the diamond. I didn't believe you or Garry; now I do because I saw proof of the research.

Did I do such statement ? also I did not see such statement from Garry. May be I missed something.


IF you speak about classical round cut then some combinations of Pavilion angles with high crown gives higher Dispersion.
For Example Dodson theoretically found combination P40Cr40( if i remember correctly. Last time I read Dodson work around 15 years ago)

For Fun we optimized Round Cut for high Dispersion and LR above 90% from Tolkowsky Cut.
see samples 15-18 in our MSS list.
http://www.octonus.com/oct/mss/

you may see several MSS videos in same time
check it in mono https://www.dropbox.com/s/mexydiv49rnnjqy/AllMSSVibox2012December.mov

better download movie and see it in Octonus Player https://www.dropbox.com/sh/4gyqblc6nwsc5y0/fa0rGEiXF-

If you have stereo monitor you may compare Fire appearance for same diamond in mono and stereo.
https://www.dropbox.com/sh/g47tpldsnfnblcf/yleTJZEzId

we found it theoretically by Diamcalc in Mono for several static views because we did it around 5-7 years ago. in this time we had not Metrics for Fire which account Stereo observation in Dynamic ( Stereo and Dynamic is Critical for correct Fire grade).





_______

I think that statements such as "brightness is the enemy of fire" are unhelpful, even unintentionally misleading, to a consumer. It suggests in his/her mind that a diamond will almost always look bright or almost always look fiery.

if "brightness is the enemy of fire", it does not mean that any dark stone has a lot fire.
But the diamond with highest fire which I even saw in my life was very dark.( this very dark diamond has highest fire for my private test. I never measured Fire for this diamond, I have not neither 3D model nor single photo for this diamond )

"brightness is the enemy of fire" is hyperbola statement . may be more correct statement " no one diamond can not have Highest Brightness and Highest Fire in same time" . If You optimize cut for Fire you lose some brightness and via versa if you optimize cut for brightness then you lose some Fire.

Well, here's something to think about--a diamond that looks very bright to the wearer will likely look every bit as fiery as a "fire-prone" diamond to an observer across the table (say, 3 ft; 100 cm away). I'd bet most people on PriceScope have no idea that this is the case.

One should just state that certain characteristics of this diamond favor seeing colored light more often than bright white light in certain conditions. End of story.

_______

Re: use of the HCA for predicting brightness, fire, and scint: now that I see the fire, brightness, and scintillation trends that the HCA purports to "grade" (I know--bad word, but I can't think of a better description), I think it would be much more helpful to have a few comparison diamonds to say "Your diamond will likely be a little less fiery than Example A, etc".

As far as grading brightness, maybe a more helpful grade would be to use the ASET image of the Tolk. ideal as a benchmark of both brightness AND contrast. As has been stated here, brightness alone has little beauty without dynamic contrast.


ASET does not give any information neither about Fire, nor about Dynamical contrast, and of course does not account stereo observation phenomenas . Even Head obscuration is not correct in ASET because it uses Cyclops observation model. End story.

 

[Karl_K]

"brightness is the enemy of fire" is hyperbola statement . may be more correct statement " no one diamond can not have Highest Brightness and Highest Fire in same time" . If You optimize cut for Fire you lose some brightness and via versa if you optimize cut for brightness then you lose some Fire.[/color]

Bingo, To optimize brightness you want the light to go in and right out with the min. amount of bending.
To get increased fire you need to bend and disperse the light more which results in less light being returned towards the viewer.
However with careful design you can get high amounts of both.
One trueism of diamond design that a diamond cut for a specific lighting will always out perform a generalist in that lighting. Designing a diamond that works well in all lighting is much harder.
Because people are in many different lighting conditions during a day they all have to be taken into account.

 

[Serg]

Sergey,

While your smilies above are inappropriate,


Paul,
Really ? I did not find better response . Did you read your posts?
what did happened with you? too much nice Belgium beer ?

I agree with you that contrast is going to increase the likelihood of observing fire.

So, please explain to me, after Garry first ignored, then avoided the matter and eventually ran off, how can the HCA with its limited input-variables predict such contrast?

I am not developer neither of HCA nor of GIA cut grading ( rejection) system.
I do not see big difference in abilities of these two rejection tools.
Both of them use Ideal symmetry round cuts as reference for some combinations of Optical appearance.
you may find proportion set with high contrast or Fire or Brightness or brilliance and then use:
1) It as reference
2) Use simple rule for round cut " To minimize Optical appearance changes you have to change Pavilion and Crown angles in opposite directions with certain ratio . To maximize Optical appearance changes you have to move in perpendicular direction( change Angles in same directions)

to build rejection system."

Btw . AGS system has in fundament same Idea( it is not clear from first point of view, but if think deeply enough about ASET technology then you will see it. It is reason why I consider ASG system as rejection system too, similar as HCA and GIA cut grading (rejection) system.
the difference just in input data( 3D model instead of parameters )


It is what got this thread started, and all statements here (and I agree with almost all of what you and Garry have said) indicate that the HCA cannot give such a prediction.

So, please indulge me, train me, teach me.

Live long,

 

[Paul-Antwerp]

Too much beer, I do not think so.

Reading another post of yours today, it seems you have been delving too much into wine this morning . But I will take time to ask you about that tomorrow.

So, in short, trying to understand your current post, you agree with me that the HCA cannot predict the observation of fire in a meaningful way?

Live long,

 

[Serg]

One more link for Teobl

http://www.gemology.ru/cut/english/document4_4.htm

it is link to one page our research had been published in 1999 on our site.

 

[Serg]

Too much beer, I do not think so.

Reading another post of yours today, it seems you have been delving too much into wine this morning . But I will take time to ask you about that tomorrow.

So, in short, trying to understand your current post, you agree with me that the HCA cannot predict the observation of fire in a meaningful way?

Live long,

see Ptolemy world map.
Was it done in "Meaningful way " in Ptolemy time?

What is "Meaningful way " in 2013 for Cut grading ?

 

[Paul-Antwerp]

Thank you for the confirmation, Sergey.

Now, let's move on.

 

[Serg]

Thank you for the confirmation, Sergey.

Now, let's move on.

Ptolemy did very important step in World map design . His work was very helpful for him contemporaries and his method had been used by future World Map creators.

You need think more about what type confirmation you have just received from me.


"Ptolemy put all this information into a grand scheme. Following Marinos, he assigned coordinates to all the places and geographic features he knew, in a grid that spanned the globe. Latitude was measured from the equator, as it is today, but Ptolemy preferred book 8 to express it as the length of the longest day rather than degrees of arc (the length of the midsummer day increases from 12h to 24h as one goes from the equator to the polar circle). In books 2 through 7, he used degrees and put the meridian of 0 longitude at the most western land he knew, the "Blessed Islands", probably the Cape Verde islands (not the Canary Islands, as long accepted) as suggested by the location of the six dots labelled the "FORTUNATA" islands near the left extreme of the blue sea of Ptolemy's map here reproduced.



A 15th-century manuscript copy of the Ptolemy world map, reconstituted from Ptolemy's Geographia (circa 150), indicating the countries of "Serica" and "Sinae" (China) at the extreme east, beyond the island of "Taprobane" (Sri Lanka, oversized) and the "Aurea Chersonesus" (Malay Peninsula).
Ptolemy also devised and provided instructions on how to create maps both of the whole inhabited world (oikoumenè) and of the Roman provinces. In the second part of the Geographia, he provided the necessary topographic lists, and captions for the maps. His oikoumenè spanned 180 degrees of longitude from the Blessed Islands in the Atlantic Ocean to the middle of China, and about 80 degrees of latitude from Shetland to anti-Meroe (east coast of Africa); Ptolemy was well aware that he knew about only a quarter of the globe, and an erroneous extension of China southward suggests his sources did not reach all the way to the Pacific Ocean."
https://en.wikipedia.org/wiki/Ptolemy

 

[Garry H (Cut Nut)]

"brightness is the enemy of fire" is hyperbola statement . may be more correct statement " no one diamond can not have Highest Brightness and Highest Fire in same time" . If You optimize cut for Fire you lose some brightness and via versa if you optimize cut for brightness then you lose some Fire.[/color]

Bingo, To optimize brightness you want the light to go in and right out with the min. amount of bending.
To get increased fire you need to bend and disperse the light more which results in less light being returned towards the viewer.
However with careful design you can get high amounts of both.
One trueism of diamond design that a diamond cut for a specific lighting will always out perform a generalist in that lighting. Designing a diamond that works well in all lighting is much harder.
Because people are in many different lighting conditions during a day they all have to be taken into account.

Thanks Karl.
And it is no surprise that along the sweet inverse proportion line (that Bruce Harding and a few others of us discovered independently) for round cuts that runs from shallow crown brighter diamonds to steeper crown firey (but still brighter than stones off that sweet line) that I am able to interpret the data from DiamCalc Pro (not the basic DC), together with my own experience of looking at real diamonds in various lighting environments, as I do daily) and make an assessment to plug into HCA.

I hope everyone (even Paul, after he gets over his hangover) has gained some benefit from this discussion. The poll has indicated to me that i need to weight fire more highly. In the first HCA I weighted light return (brilliance or brightness or whatever we are calling it) 2X more highly than fire. I now think to give them equal weighting. This will probably mean the inclusion of some slightly steeper deeper stones, especially when combined with dark zone data that I am using to account for scintillation (ugly largish dead zones, because as in Sergey's definition of B,F & S that he posted - scintillation is also not well enough understood to be definitive.

so Paul, FYI - I have been writting a detailed account of the methods and processes I have been using for this iteration of the HCA data as i have been doing it these past few months. When complete I will share it when the app is completed.

 

[Paul-Antwerp]

Sergey,

I have a question about that diamond with the highest fire in your personal observations.

Teobl,

if "brightness is the enemy of fire", it does not mean that any dark stone has a lot fire.
But the diamond with highest fire which I even saw in my life was very dark.( this very dark diamond has highest fire for my private test. I never measured Fire for this diamond, I have not neither 3D model nor single photo for this diamond )

[/quote]

So, you are saying that in a light-environment, most suitable for observing brightness, this particular diamond for you, the oserver, was very dark. Correct me if I am wrong, but I understand that you mean that most of that diamond's surface was dark to your eyes. If you mean something else, please clarify.

Then, changing the light-environment to one more suitable for observing fire, you found this same diamond (same observer too) to give very high fire.

Logically, I would think that the fire observed by you can only come from the area that was bright in the brightness-friendly environment. It cannot possibly come from the dark zone, can it?

And for your info, still not drinking. My questions may be too simple for you, but they still deserve a genuine answer.

Live long,

 

[Serg]

Sergey,

I have a question about that diamond with the highest fire in your personal observations.

Teobl,

if "brightness is the enemy of fire", it does not mean that any dark stone has a lot fire.
But the diamond with highest fire which I even saw in my life was very dark.( this very dark diamond has highest fire for my private test. I never measured Fire for this diamond, I have not neither 3D model nor single photo for this diamond )

re:So, you are saying that in a light-environment, most suitable for observing brightness, this particular diamond for you, the oserver, was very dark. Correct me if I am wrong, but I understand that you mean that most of that diamond's surface was dark to your eyes. If you mean something else, please clarify.


"Right. Diamond had most only two type facets
a) Completely dark ( around 60-80% visible surface)
b) Fire flashes ( around 20% visible surface)
I saw diamond from different positions and fire flashes danced on diamond surface
"

re:Then, changing the light-environment to one more suitable for observing fire, you found this same diamond (same observer too) to give very high fire.

Wrong. I had not any ability to change anything except my position. I saw this diamond in Russian Diamond Fond.
in same window in Same time( similar lights) I saw other cuts( include round cut) with High Brilliancy (. just Ordinary 10 Ct round diamonds with high brilliancy and reasonable fire, but very boring in same light conditions)

re:Logically, I would think that the fire observed by you can only come from the area that was bright in the brightness-friendly environment. It cannot possibly come from the dark zone, can it?

I think it is possible to create cut that reflect either "near Zero light" or Fire, at least for standard spot lights.

re:And for your info, still not drinking.

anything else ?

My questions may be too simple for you, but they still deserve a genuine answer.

Live long,[/quote]

 

[Paul-Antwerp]

Sergey,

I have a question about that diamond with the highest fire in your personal observations.

Teobl,

if "brightness is the enemy of fire", it does not mean that any dark stone has a lot fire.
But the diamond with highest fire which I even saw in my life was very dark.( this very dark diamond has highest fire for my private test. I never measured Fire for this diamond, I have not neither 3D model nor single photo for this diamond )

re:So, you are saying that in a light-environment, most suitable for observing brightness, this particular diamond for you, the oserver, was very dark. Correct me if I am wrong, but I understand that you mean that most of that diamond's surface was dark to your eyes. If you mean something else, please clarify.


"Right. Diamond had most only two type facets
a) Completely dark ( around 60-80% visible surface)
b) Fire flashes ( around 20% visible surface)
I saw diamond from different positions and fire flashes danced on diamond surface
"

re:Then, changing the light-environment to one more suitable for observing fire, you found this same diamond (same observer too) to give very high fire.

Wrong. I had not any ability to change anything except my position. I saw this diamond in Russian Diamond Fond.
in same window in Same time( similar lights) I saw other cuts( include round cut) with High Brilliancy (. just Ordinary 10 Ct round diamonds with high brilliancy and reasonable fire, but very boring in same light conditions)

re:Logically, I would think that the fire observed by you can only come from the area that was bright in the brightness-friendly environment. It cannot possibly come from the dark zone, can it?

I think it is possible to create cut that reflect either "near Zero light" or Fire, at least for standard spot lights.

re:And for your info, still not drinking.

anything else ?

My questions may be too simple for you, but they still deserve a genuine answer.

Live long,

[/quote]

I need to ask again, Sergey, for the sake of clarity,

When you saw that fiery diamond, it was in a light-environment more inclined to show brightness? In other words, it was not in spot lighting with small light sources?

And there, you saw a diamond 60 to 80% dark, and the rest, you observed as fire?

Then, theoretically, if one would move that same diamond (let's keep the observer constant too) to a light-environment more inclined to show fire, what would theoretically happen?
- I think that 60 to 80% of the diamond remains dark,
- And of the remaining surface, a much smaller part (depending on the number of light sources) will show fire, with the remainder also being dark.

Is it unrealistic to expect that same diamond to be 95% or more dark in an environment with only spotlights?

Live long,

 

[Serg]

Sergey,

I have a question about that diamond with the highest fire in your personal observations.

Teobl,

if "brightness is the enemy of fire", it does not mean that any dark stone has a lot fire.
But the diamond with highest fire which I even saw in my life was very dark.( this very dark diamond has highest fire for my private test. I never measured Fire for this diamond, I have not neither 3D model nor single photo for this diamond )

re:So, you are saying that in a light-environment, most suitable for observing brightness, this particular diamond for you, the oserver, was very dark. Correct me if I am wrong, but I understand that you mean that most of that diamond's surface was dark to your eyes. If you mean something else, please clarify.


"Right. Diamond had most only two type facets
a) Completely dark ( around 60-80% visible surface)
b) Fire flashes ( around 20% visible surface)
I saw diamond from different positions and fire flashes danced on diamond surface
"

re:Then, changing the light-environment to one more suitable for observing fire, you found this same diamond (same observer too) to give very high fire.

Wrong. I had not any ability to change anything except my position. I saw this diamond in Russian Diamond Fond.
in same window in Same time( similar lights) I saw other cuts( include round cut) with High Brilliancy (. just Ordinary 10 Ct round diamonds with high brilliancy and reasonable fire, but very boring in same light conditions)

re:Logically, I would think that the fire observed by you can only come from the area that was bright in the brightness-friendly environment. It cannot possibly come from the dark zone, can it?

I think it is possible to create cut that reflect either "near Zero light" or Fire, at least for standard spot lights.

re:And for your info, still not drinking.

anything else ?

My questions may be too simple for you, but they still deserve a genuine answer.

Live long,

I need to ask again, Sergey, for the sake of clarity,

When you saw that fiery diamond, it was in a light-environment more inclined to show brightness? In other words, it was not in spot lighting with small light sources?

And there, you saw a diamond 60 to 80% dark, and the rest, you observed as fire?

Then, theoretically, if one would move that same diamond (let's keep the observer constant too) to a light-environment more inclined to show fire, what would theoretically happen?
- I think that 60 to 80% of the diamond remains dark,
- And of the remaining surface, a much smaller part (depending on the number of light sources) will show fire, with the remainder also being dark.

Is it unrealistic to expect that same diamond to be 95% or more dark in an environment with only spotlights?

Live long,[/quote]

Paul,

I will not play in your Games with your rules. I do not like games at all,I prefer work and results.
If you want understand something, then just re-read :
1) my above posts
2) Your Above posts, and specially most funny your post " by Paul-Antwerp » 07 Jul 2013 07:53"
3) Peter Presentations about Fire
And Think as you can safe you face without games and without wasting time again and again.
Nobody can teach you ( even Peter Y.) if you do not like to learn and listen .
Good luck you to find You. you completely lost You and subject . Sad.

 

[Paul-Antwerp]

Number two running away from his own words?

It seems to be a pattern.

Here was a guy (a so-called well-respected 'scientist), who does not want to explain a simple question. Oh yes, he has seen the most fiery diamond ever, and it was between 60 and 80% dark in conditions, most inclined to make it bright!!! Logically, next question then is, what happens to that diamond in conditions with less and smaller light sources, more inclined to bring about the observation of fire.

He has the choice between saying:

- Option 1: Well, the diamond, in all the dark areas that were dark while a lot of light was pumped into it, cannot possibly suddenly generate light in those areas, so those remain dark. And of all the non-dark, fiery areas in the original condition, now, only a fraction are lighting up with fire. As a result, the maximum limit of 'potential fire' is the potential maximum brightness of that same diamond.
- Option 2: I give up, you are a sad and pitiful person, who does not want to learn.

Apparently option 2 was chosen. Why? Who knows? I cannot imagine that it is in the spirit of teaching, for which PS is supposed to stand.

Sad? Sad, indeed!!!

Live long,

 

[Serg]

Number two running away from his own words?

It seems to be a pattern.

Here was a guy (a so-called well-respected 'scientist), who does not want to explain a simple question.

I happy give answer to either simple or complex questions.
But I ignore fake questions and "games "

Oh yes, he has seen the most fiery diamond ever, and it was between 60 and 80% dark in conditions, most inclined to make it bright!!! Logically, next question then is, what happens to that diamond in conditions with less and smaller light sources, more inclined to bring about the observation of fire.

He has the choice between saying:

- Option 1: Well, the diamond, in all the dark areas that were dark while a lot of light was pumped into it, cannot possibly suddenly generate light in those areas, so those remain dark. And of all the non-dark, fiery areas in the original condition, now, only a fraction are lighting up with fire. As a result, the maximum limit of 'potential fire' is the potential maximum brightness of that same diamond.

If I had only one reasonable answer from your point of you, why you asked me? you knew your answer.
If you want play in such games you have to find other partner who is agree to wasting time .

you missed most points in this discussion. I will remind it you several months latter.

- Option 2: I give up, you are a sad and pitiful person, who does not want to learn.

Apparently option 2 was chosen. Why? Who knows? I cannot imagine that it is in the spirit of teaching, for which PS is supposed to stand.

Sad? Sad, indeed!!!

Live long,

I confirm all my statements in this discussion.

 

[Garry H (Cut Nut)]

I think this could be the diamond Sergey?
http://www.antique-jewelry-investor.com/kremlin-diamonds.html
But this phot is not taken in the same lighting that I saw the stone more than a decade ago.
As I recall it was in a hip to head height showcase with beige velvet walls and halogen downlights.
The showcase to the right of the people in this photo
http://old.rian.ru/spravka/20100203/207377641.html

Paul your questioning is hard to follow.

 

[Serg]

I think this could be the diamond Sergey?
http://www.antique-jewelry-investor.com/kremlin-diamonds.html
But this phot is not taken in the same lighting that I saw the stone more than a decade ago.
As I recall it was in a hip to head height showcase with beige velvet walls and halogen downlights.
The showcase to the right of the people in this photo
http://old.rian.ru/spravka/20100203/207377641.html

Paul your questioning is hard to follow.

Garry,

No.
it was nameless diamond, stepcut with rhomb girdle shape.

Orloff diamond has not anything special except size and history .

Both of them were in same room, but may be in different showcases. most probably Orlov was in central showcase , but Fire diamond was in right bottom corner of Left showcase.

For Orloff diamond we spent seconds, for Fire diamond we spent minutes

 

[Texas Leaguer]

For future readers of the thread, a deleted post led me to find Peter Yantzer and the AGS lab's research on these topics; specifically, how cut proportions affect brilliance, fire, and scintillation. It has been the single most helpful article I've ever read on diamond light performance, and it addressed every discussion point of this thread.

http://www.agslab.com/spie/spie_lo_res.pdf

The new Scintillation report that AGS will be rolling out should be a help to consumers in getting feel for the optical properties that are most important to them in a given diamond. There are seperate metrics for flash and fire scintillation as well as a pattern map. It should provide some indication of the "flavor" of the diamond.

Here is another ealier study by GIA on the subject. For those that don't want to devote to the whole article, the conclusions are worth reading.
http://www.gia.edu/pdfs/Fall_2001_Cut.pdf