Optimizing Fire in the Modern RB Fiery Ideal Cut (FIC) how far can we go without serious detracting

[ChunkyCushionLover]

Dear PSers,

Recently I was asked to grade 2 diamonds in the MSS fire series 17,18 found here http://www.octonus.com/oct/mss/. Although I am not a grader most of the information about these stones is available including Helium Scan Data, Actual Idealscope Images, DiamCalc evaluation based on Helium scan, .gem files and GIA and AGS-PGS grading so I could simple comment on the wealth of information already available.

These designs developed by starting with AGS0 near Tolkowsky Ideal Cut and then some proportions were varied like Crown Angle, Pavillion Angle and Lower Girdle Facets, Star facets to develop a design thought to maximize fire more so than the well balanced Hearts and Arrows TICs that we general see sold and often reccomended here.

First I looked at the .gem files under various lighting and tilt angles and finally the actual Idealscope image which confirmed what I was seeing some assymetry and leakage under the table.
My first thought was why does any new diamond design optimized for fire have to be assymetric and contain leakage under the table surely a better design is possible??

These were designed over two years ago what does the most modern FIC look like?

Karl K has suggested a rough limit of 50T/80lgf/37c/40.5P/45 stars as a close to the edge of a well balanced FIC.
Has anyonel tried to optimize the steeper crown and balance the tradeoffs using DiamCalc?

What would be the limit of an FIC given that the sacrifice in brilliance, and leakage and spread cannot be too great. Please support by a real diamond or at least a theoretical picture and images of the proposed FIC.

I also hope people would answer the following as well?

i) Is there an acceptable way to measure fire experimentally? If so how?
ii) Theoretically for cut design is it enough to use the Dispersion in DiamCalc or what else would need to be used?
iii) Do consumers really care about the intensity of fire or just the size of the flash? Is this the major drawback to marketing and selling this type of diamond or is it just the loss of spread and weight that are the most important factors preventing this type of diamond from being more common?

 

[ChunkyCushionLover]

Picture Renamed

 

[Serg]

CCL,
re:ii) Theoretically for cut design is it enough to use the Dispersion in DiamCalc or what else would need to be used?


Defiantly it is not enough

what is better One big colorful flash or two small ( smaller) colorful flashes?
what is better On Bright colorful flash or two colorful flash with less brightness?

what is better when you see two color flashes all time or when you see sometimes 1 flashes but in other time 3 flashes( 0 and 4 flashes?)

3 flashes in one zone( table for example) or two flashes in different Zones?( one under table other under crown facets)

Where is boundary?

you can create many similar questions.

Main question How could you grade Fire in real diamond. Good answer good significantly increase speed of developing new Fire cuts

BTW. After these two years old tests we changed our ETASFire metrics to calculate separately metrics for table and crown facets

 

[ChunkyCushionLover]

Date: 1/26/2010 3:16:09 AM
Author: Serg
CCL,
re:ii) Theoretically for cut design is it enough to use the Dispersion in DiamCalc or what else would need to be used?


Defiantly it is not enough

what is better One big colorful flash or two small ( smaller) colorful flashes?
what is better On Bright colorful flash or two colorful flash with less brightness?

what is better when you see two color flashes all time or when you see sometimes 1 flashes but in other time 3 flashes( 0 and 4 flashes?)

3 flashes in one zone( table for example) or two flashes in different Zones?( one under table other under crown facets)

Where is boundary?

you can create many similar questions.

Main question How could you grade Fire in real diamond. Good answer good significantly increase speed of developing new Fire cuts

BTW. After these two years old tests we changed our ETASFire metrics to calculate separately metrics for table and crown facets

https://www.pricescope.com/idealbb/email.asp?mode=send&postID=2306661&catID=1&forumID=3&mtype=reply&pageNo=5&num=30
Crown 41.1 Pavillion 34.9 see the images. In the fire images do you subtract out brilliance to isolate fire? http://www.diamond-cut.com.au/12_fire.htm if so then I would be worried that the difference in fire in real life is not as great as being shown from the images given the stone is already bright in other areas.




My concern is that if you subtract out brilliance to determine fire those areas of leakage are not

 

[Serg]

Date: 1/26/2010 10:27:26 AM
Author: ChunkyCushionLover

Date: 1/26/2010 3:16:09 AM

Author: Serg

CCL,

re:ii) Theoretically for cut design is it enough to use the Dispersion in DiamCalc or what else would need to be used?



Defiantly it is not enough


what is better One big colorful flash or two small ( smaller) colorful flashes?

what is better On Bright colorful flash or two colorful flash with less brightness?


what is better when you see two color flashes all time or when you see sometimes 1 flashes but in other time 3 flashes( 0 and 4 flashes?)


3 flashes in one zone( table for example) or two flashes in different Zones?( one under table other under crown facets)


Where is boundary?


you can create many similar questions.


Main question How could you grade Fire in real diamond. Good answer good significantly increase speed of developing new Fire cuts


BTW. After these two years old tests we changed our ETASFire metrics to calculate separately metrics for table and crown facets

https://www.pricescope.com/idealbb/email.asp?mode=send&postID=2306661&catID=1&forumID=3&mtype=reply&pageNo=5&num=30

Crown 41.1 Pavillion 34.9 see the images. In the fire images do you subtract out brilliance to isolate fire? http://www.diamond-cut.com.au/12_fire.htm if so then I would be worried that the difference in fire in real life is not as great as being shown from the images given the stone is already bright in other areas.






My concern is that if you subtract out brilliance to determine fire those areas of leakage are not

CCL,

very strange post. Please try clarify your definition of Fire.
I never subtract Brilliancy from Fire because Fire does not include Brilliancy

 

[whatmeworry]

Date: 1/26/2010 3:16:09 AM
Author: Serg
CCL,

re:ii) Theoretically for cut design is it enough to use the Dispersion in DiamCalc or what else would need to be used?



Defiantly it is not enough


what is better One big colorful flash or two small ( smaller) colorful flashes?

what is better On Bright colorful flash or two colorful flash with less brightness?


what is better when you see two color flashes all time or when you see sometimes 1 flashes but in other time 3 flashes( 0 and 4 flashes?)


3 flashes in one zone( table for example) or two flashes in different Zones?( one under table other under crown facets)


Where is boundary?


you can create many similar questions.


Main question How could you grade Fire in real diamond. Good answer good significantly increase speed of developing new Fire cuts


BTW. After these two years old tests we changed our ETASFire metrics to calculate separately metrics for table and crown facets

Serg, I will give my preference for fire here and maybe you can tell me how my taste for fire can be judged by a single metric for fire. I already know the answer is no, so I contend that any grading system that only has one metric for fire is incomplete at best

1. Speed and size matter. I like large flashes and I like the frequency of them. Rounds have better fire in my opinion that princess (flashes too small) or emerald cuts (flashes too infrequent). In that respect, localization matters (for example localized to table only) in that it gives the perception to speed. But in another respect the lack of localization also matters because I also want the entire diamond to be alive.
2. Color and diversity of colors matter. I like to see all colors of the rainbow.
3. As I mentioned in the other post, I have an average looking diamond that has incredible scintillation. It is very localized to the table but the size and frequency of the flashes are incredible. I have a theory that the asymmetry of this diamond contributes to its scintillation. The locations of the flashes are random, very much like electrical sparks. But on the other hand I also like the fluid nature of the flashes from the more optically symmetrical round brilliant. Yes, this is a contradiction but consumers sometimes have contradictory tastes. I find the the distribution of fire in emerald cuts too linear for my taste.

This is related to the other posts, that while cut grading systems (AGS,GIA,IS, ASET, HCA, Brilliant Scope, etc.) are useful, they are unable to account for taste or to make meaningful tradeoffs. Because as you have said,these are all rejection tools and not selection tools.

 

[Karl_K]

Date: 1/26/2010 12:00:15 PM
Author: whatmeworry


Serg, I will give my preference for fire here and maybe you can tell me how my taste for fire can be judged by a single metric for fire. I already know the answer is no, so I contend that any grading system that only has one metric for fire is incomplete at best


1. Speed and size matter. I like large flashes and I like the frequency of them. Rounds have better fire in my opinion that princess (flashes too small) or emerald cuts (flashes too infrequent). In that respect, localization matters (for example localized to table only) in that it gives the perception to speed. But in another respect the lack of localization also matters because I also want the entire diamond to be alive.

2. Color and diversity of colors matter. I like to see all colors of the rainbow.

3. As I mentioned in the other post, I have an average looking diamond that has incredible scintillation. It is very localized to the table but the size and frequency of the flashes are incredible. I have a theory that the asymmetry of this diamond contributes to its scintillation. The locations of the flashes are random, very much like electrical sparks. But on the other hand I also like the fluid nature of the flashes from the more optically symmetrical round brilliant. Yes, this is a contradiction but consumers sometimes have contradictory tastes. I find the the distribution of fire in emerald cuts too linear for my taste.


This is related to the other posts, that while cut grading systems (AGS,GIA,IS, ASET, HCA, Brilliant Scope, etc.) are useful, they are unable to account for taste or to make meaningful tradeoffs. Because as you have said,these are all rejection tools and not selection tools.

Interesting.
That is one reason I target medium virtual facets in my designs.
Large enough to be bright, small enough there is a ton of flashes.
They also tend to produce intense fire.
That way I don't have to trade brilliance for fire and scintillation.
I can have all 3.
Uniform symmetry in an RB maximizes the amount of med VF's but sometimes they just fall into place in others but it is more luck than design.

 

[Karl_K]

In answer to the original topic it depends on usage.
The problem with shallow pavilions is obstruction and different uses have different amounts of obstruction.
Long lower girdles help with obstruction issues.

In general anything under ~40.4 sometimes 40.5 will have issues in a ring with any crown.
That can be minimized with long lowers but then you change the mix of virtual facets.
There is no free lunch.

"Karl K has suggested a rough limit of 50T/80lgf/37c/40.5P/45 stars as a close to the edge of a well balanced FIC."
That would be very close to the ultimate FIC in my opinion.
I wouldn't push it much further.

 

[ChunkyCushionLover]

Date: 1/26/2010 12:51:17 PM
Author: Karl_K
In answer to the original topic it depends on usage.
The problem with shallow pavilions is obstruction and different uses have different amounts of obstruction.
Long lower girdles help with obstruction issues.

In general anything under ~40.4 sometimes 40.5 will have issues in a ring with any crown.
That can be minimized with long lowers but then you change the mix of virtual facets.
There is no free lunch.

''Karl K has suggested a rough limit of 50T/80lgf/37c/40.5P/45 stars as a close to the edge of a well balanced FIC.''
That would be very close to the ultimate FIC in my opinion.
I wouldn''t push it much further.

Could you please create a .gem file with those paramaters and/or post the idealscope image in this thread.

Thanks,

CCl

 

[Serg]

Date: 1/26/2010 12:00:15 PM
Author: whatmeworry

Date: 1/26/2010 3:16:09 AM

Author: Serg

CCL,


re:ii) Theoretically for cut design is it enough to use the Dispersion in DiamCalc or what else would need to be used?




Defiantly it is not enough



what is better One big colorful flash or two small ( smaller) colorful flashes?


what is better On Bright colorful flash or two colorful flash with less brightness?



what is better when you see two color flashes all time or when you see sometimes 1 flashes but in other time 3 flashes( 0 and 4 flashes?)



3 flashes in one zone( table for example) or two flashes in different Zones?( one under table other under crown facets)



Where is boundary?



you can create many similar questions.



Main question How could you grade Fire in real diamond. Good answer good significantly increase speed of developing new Fire cuts



BTW. After these two years old tests we changed our ETASFire metrics to calculate separately metrics for table and crown facets

Serg, I will give my preference for fire here and maybe you can tell me how my taste for fire can be judged by a single metric for fire. I already know the answer is no, so I contend that any grading system that only has one metric for fire is incomplete at best


1. Speed and size matter. I like large flashes and I like the frequency of them. Rounds have better fire in my opinion that princess (flashes too small) or emerald cuts (flashes too infrequent). In that respect, localization matters (for example localized to table only) in that it gives the perception to speed. But in another respect the lack of localization also matters because I also want the entire diamond to be alive.

2. Color and diversity of colors matter. I like to see all colors of the rainbow.

3. As I mentioned in the other post, I have an average looking diamond that has incredible scintillation. It is very localized to the table but the size and frequency of the flashes are incredible. I have a theory that the asymmetry of this diamond contributes to its scintillation. The locations of the flashes are random, very much like electrical sparks. But on the other hand I also like the fluid nature of the flashes from the more optically symmetrical round brilliant. Yes, this is a contradiction but consumers sometimes have contradictory tastes. I find the the distribution of fire in emerald cuts too linear for my taste.


This is related to the other posts, that while cut grading systems (AGS,GIA,IS, ASET, HCA, Brilliant Scope, etc.) are useful, they are unable to account for taste or to make meaningful tradeoffs. Because as you have said,these are all rejection tools and not selection tools.

WmW, Thanks for your post. I hope somebody from companies what produce IDEAL RBC will read it, specially below part

"As I mentioned in the other post, I have an average looking diamond that has incredible scintillation. It is very localized to the table but the size and frequency of the flashes are incredible. I have a theory that the asymmetry of this diamond contributes to its scintillation. The locations of the flashes are random, very much like electrical sparks. But on the other hand I also like the fluid nature of the flashes from the more optically symmetrical round brilliant. Yes, this is a contradiction but consumers sometimes have contradictory tastes. I find the the distribution of fire in emerald cuts too linear for my taste."

Unfortunately question about boundaries is open yet

 

[oldminer]

Decide on the size and number of fire flashes you wish to see. Do you want large flashes or more numerous small flashes? Keep in mind that a diamond with truly unusal amounts of fire will give up some light return and be less commercial, mainstream, successful most likely. Also, fire results from the lighting used and is inherent in diamond if the lighting is right, fire will show.

It can be nmeasured digitally, but this may not equate to what you or someone else thinks looks best. We can count colored pixels, but it may be correct yet seem wrong to the human eye of some observers. It is not going to be a simple, objective project.

 

[Garry H (Cut Nut)]

Date: 1/26/2010 10:43:51 AM
Author: Serg

Date: 1/26/2010 10:27:26 AM
Author: ChunkyCushionLover

Date: 1/26/2010 3:16:09 AM

Author: Serg

CCL,

re:ii) Theoretically for cut design is it enough to use the Dispersion in DiamCalc or what else would need to be used?



Defiantly it is not enough


what is better One big colorful flash or two small ( smaller) colorful flashes?

what is better On Bright colorful flash or two colorful flash with less brightness?


what is better when you see two color flashes all time or when you see sometimes 1 flashes but in other time 3 flashes( 0 and 4 flashes?)


3 flashes in one zone( table for example) or two flashes in different Zones?( one under table other under crown facets)


Where is boundary?


you can create many similar questions.


Main question How could you grade Fire in real diamond. Good answer good significantly increase speed of developing new Fire cuts


BTW. After these two years old tests we changed our ETASFire metrics to calculate separately metrics for table and crown facets

https://www.pricescope.com/idealbb/email.asp?mode=send&postID=2306661&catID=1&forumID=3&mtype=reply&pageNo=5&num=30

Crown 41.1 Pavillion 34.9 see the images. In the fire images do you subtract out brilliance to isolate fire? http://www.diamond-cut.com.au/12_fire.htm if so then I would be worried that the difference in fire in real life is not as great as being shown from the images given the stone is already bright in other areas.






My concern is that if you subtract out brilliance to determine fire those areas of leakage are not

CCL,

very strange post. Please try clarify your definition of Fire.
I never subtract Brilliancy from Fire because Fire does not include Brilliancy

CCL you are probably referring to this comment at the end of my Diamond-cut.com.au secton?
"However we must always remember that excessive brilliance will drown out potential fire."

Try this experiment - sit diamond still on desk / table, with one or a few strong small point lights (eg halogen in ceiling) - sit very still and move until you look at one very strong bright white flash. Now move left and right (or to and away) and you will see the flash tails off to blue one way and red the other way. Move closer and there will be less color - more white. Now move away and there will be more color and less white. Move to the other side of room or stand up on a chair and that flash will have little or no white and you will begin to see the green in the center of the spectrum.

 

[ChunkyCushionLover]

Date: 1/26/2010 6:00:22 PM
Author: Garry H (Cut Nut)

Date: 1/26/2010 10:43:51 AM
Author: Serg

Date: 1/26/2010 10:27:26 AM
Author: ChunkyCushionLover

Date: 1/26/2010 3:16:09 AM

Author: Serg

CCL,

re:ii) Theoretically for cut design is it enough to use the Dispersion in DiamCalc or what else would need to be used?



Defiantly it is not enough


what is better One big colorful flash or two small ( smaller) colorful flashes?

what is better On Bright colorful flash or two colorful flash with less brightness?


what is better when you see two color flashes all time or when you see sometimes 1 flashes but in other time 3 flashes( 0 and 4 flashes?)


3 flashes in one zone( table for example) or two flashes in different Zones?( one under table other under crown facets)


Where is boundary?


you can create many similar questions.


Main question How could you grade Fire in real diamond. Good answer good significantly increase speed of developing new Fire cuts


BTW. After these two years old tests we changed our ETASFire metrics to calculate separately metrics for table and crown facets

https://www.pricescope.com/idealbb/email.asp?mode=send&postID=2306661&catID=1&forumID=3&mtype=reply&pageNo=5&num=30

Crown 41.1 Pavillion 34.9 see the images. In the fire images do you subtract out brilliance to isolate fire? http://www.diamond-cut.com.au/12_fire.htm if so then I would be worried that the difference in fire in real life is not as great as being shown from the images given the stone is already bright in other areas.






My concern is that if you subtract out brilliance to determine fire those areas of leakage are not

CCL,

very strange post. Please try clarify your definition of Fire.
I never subtract Brilliancy from Fire because Fire does not include Brilliancy

CCL you are probably referring to this comment at the end of my Diamond-cut.com.au secton?
''However we must always remember that excessive brilliance will drown out potential fire.''

Try this experiment - sit diamond still on desk / table, with one or a few strong small point lights (eg halogen in ceiling) - sit very still and move until you look at one very strong bright white flash. Now move left and right (or to and away) and you will see the flash tails off to blue one way and red the other way. Move closer and there will be less color - more white. Now move away and there will be more color and less white. Move to the other side of room or stand up on a chair and that flash will have little or no white and you will begin to see the green in the center of the spectrum.

Actually what I was referring to was subtracting the baseline brightness from maximum intensity to obtain the real on off "fire". It appears that the metric for dispersion doesn''t require that, but I still don''t understand why the Fire images show the greatest fire in an area with almost complete leakage.

 

[Karl_K]

Date: 1/26/2010 9:25:20 PM
Author: ChunkyCushionLover
but I still don't understand why the Fire images show the greatest fire in an area with almost complete leakage.

The pavilion mains when they return light the light is in and out.
That is why the arrows are a reflection of the opposite pavilion main.

The largest fire zone(often brightest also) in an RB is reflected off the lower halves but not in an OEC and that is because in the best oec's the mains are at the same angle range as the lowers in a RB.

http://journal.pricescope.com/Articles/68/1/Do-the-pavilion-mains-drive-light-return-in-the-modern-round-brilliant.aspx

 

[Karl_K]

here are the lowers at 41.89

 

[Karl_K]

Here are the mains at 41.89 in an oec
The crown is 35 degrees in both
notice where the fire is at now.

 

[Karl_K]

here is the mains at 41.89 with the same lgf as the first one.

notice the lowers are still partly blue at 42.96 degrees.

The simple theory is that steeper pavilions lose brightness faster than they lose fire.
So a slightly steep deep may have more apparent fire at the cost of brightness.
But that simple theory would be wrong at times because of VF size issues but that gets really really really complicated.

 

[Serg]

Date: 1/26/2010 9:25:20 PM
Author: ChunkyCushionLover

Date: 1/26/2010 6:00:22 PM

Author: Garry H (Cut Nut)

Date: 1/26/2010 10:43:51 AM

Author: Serg

Date: 1/26/2010 10:27:26 AM

Author: ChunkyCushionLover

Date: 1/26/2010 3:16:09 AM


Author: Serg


CCL,


re:ii) Theoretically for cut design is it enough to use the Dispersion in DiamCalc or what else would need to be used?




Defiantly it is not enough



what is better One big colorful flash or two small ( smaller) colorful flashes?


what is better On Bright colorful flash or two colorful flash with less brightness?



what is better when you see two color flashes all time or when you see sometimes 1 flashes but in other time 3 flashes( 0 and 4 flashes?)



3 flashes in one zone( table for example) or two flashes in different Zones?( one under table other under crown facets)



Where is boundary?



you can create many similar questions.



Main question How could you grade Fire in real diamond. Good answer good significantly increase speed of developing new Fire cuts



BTW. After these two years old tests we changed our ETASFire metrics to calculate separately metrics for table and crown facets

https://www.pricescope.com/idealbb/email.asp?mode=send&postID=2306661&catID=1&forumID=3&mtype=reply&pageNo=5&num=30


Crown 41.1 Pavillion 34.9 see the images. In the fire images do you subtract out brilliance to isolate fire? http://www.diamond-cut.com.au/12_fire.htm if so then I would be worried that the difference in fire in real life is not as great as being shown from the images given the stone is already bright in other areas.







My concern is that if you subtract out brilliance to determine fire those areas of leakage are not

CCL,


very strange post. Please try clarify your definition of Fire.

I never subtract Brilliancy from Fire because Fire does not include Brilliancy

CCL you are probably referring to this comment at the end of my Diamond-cut.com.au secton?

''However we must always remember that excessive brilliance will drown out potential fire.''


Try this experiment - sit diamond still on desk / table, with one or a few strong small point lights (eg halogen in ceiling) - sit very still and move until you look at one very strong bright white flash. Now move left and right (or to and away) and you will see the flash tails off to blue one way and red the other way. Move closer and there will be less color - more white. Now move away and there will be more color and less white. Move to the other side of room or stand up on a chair and that flash will have little or no white and you will begin to see the green in the center of the spectrum.

Actually what I was referring to was subtracting the baseline brightness from maximum intensity to obtain the real on off ''fire''. It appears that the metric for dispersion doesn''t require that, but I still don''t understand why the Fire images show the greatest fire in an area with almost complete leakage.

re:but I still don''t understand why the Fire images show the greatest fire in an area with almost complete leakage.

CCL,
these Fire images show "Fire potential " for Loose diamonds. We do not subtract outgoing Pavilion rays. Real fire results depends from Light conditions. For diamond in ring result will different .
we will add both types images a soon

 

[ChunkyCushionLover]

Date: 1/26/2010 10:10:03 PM
Author: Karl_K
here is the mains at 41.89 with the same lgf as the first one.

notice the lowers are still partly blue at 42.96 degrees.

The simple theory is that steeper pavilions lose brightness faster than they lose fire.
So a slightly steep deep may have more apparent fire at the cost of brightness.
But that simple theory would be wrong at times because of VF size issues but that gets really really really complicated.

Thank-you those three posts are really informative and helpful! I am constanly learning from your posts.

 

[ChunkyCushionLover]

Date: 1/26/2010 6:00:22 PM
Author: Garry H (Cut Nut)

Date: 1/26/2010 10:43:51 AM
Author: Serg

Date: 1/26/2010 10:27:26 AM
Author: ChunkyCushionLover

Date: 1/26/2010 3:16:09 AM

Author: Serg

CCL,

re:ii) Theoretically for cut design is it enough to use the Dispersion in DiamCalc or what else would need to be used?



Defiantly it is not enough


what is better One big colorful flash or two small ( smaller) colorful flashes?

what is better On Bright colorful flash or two colorful flash with less brightness?


what is better when you see two color flashes all time or when you see sometimes 1 flashes but in other time 3 flashes( 0 and 4 flashes?)


3 flashes in one zone( table for example) or two flashes in different Zones?( one under table other under crown facets)


Where is boundary?


you can create many similar questions.


Main question How could you grade Fire in real diamond. Good answer good significantly increase speed of developing new Fire cuts


BTW. After these two years old tests we changed our ETASFire metrics to calculate separately metrics for table and crown facets

https://www.pricescope.com/idealbb/email.asp?mode=send&postID=2306661&catID=1&forumID=3&mtype=reply&pageNo=5&num=30

Crown 41.1 Pavillion 34.9 see the images. In the fire images do you subtract out brilliance to isolate fire? http://www.diamond-cut.com.au/12_fire.htm if so then I would be worried that the difference in fire in real life is not as great as being shown from the images given the stone is already bright in other areas.






My concern is that if you subtract out brilliance to determine fire those areas of leakage are not

CCL,

very strange post. Please try clarify your definition of Fire.
I never subtract Brilliancy from Fire because Fire does not include Brilliancy

CCL you are probably referring to this comment at the end of my Diamond-cut.com.au secton?
'However we must always remember that excessive brilliance will drown out potential fire.'

Try this experiment - sit diamond still on desk / table, with one or a few strong small point lights (eg halogen in ceiling) - sit very still and move until you look at one very strong bright white flash. Now move left and right (or to and away) and you will see the flash tails off to blue one way and red the other way. Move closer and there will be less color - more white. Now move away and there will be more color and less white. Move to the other side of room or stand up on a chair and that flash will have little or no white and you will begin to see the green in the center of the spectrum.

Yes I understand what you are saying. If you add White Light to Red Light you still get white light. At an extreme angle your eye see predominantly the red longest visible spectrum wavelength of light only or the blue shortest wavelength of visible light only, and head on the whole spectrum of colours added together which will appear to be just white light.

 

[ChunkyCushionLover]

Date: 1/26/2010 3:16:59 PM
Author: oldminer
Decide on the size and number of fire flashes you wish to see. Do you want large flashes or more numerous small flashes? Keep in mind that a diamond with truly unusal amounts of fire will give up some light return and be less commercial, mainstream, successful most likely. Also, fire results from the lighting used and is inherent in diamond if the lighting is right, fire will show.

It can be nmeasured digitally, but this may not equate to what you or someone else thinks looks best. We can count colored pixels, but it may be correct yet seem wrong to the human eye of some observers. It is not going to be a simple, objective project.

So then that would explain why no vendor is marketing this type of cut. The closest I have seen is the GOG August Vintage Rounds, which we call OECs which are still near Tolkowsky rounds with much shorter LGFs.

 

[yssie]

Date: 1/28/2010 1:46:57 AM
Author: ChunkyCushionLover

Date: 1/26/2010 6:00:22 PM
Author: Garry H (Cut Nut)








CCL you are probably referring to this comment at the end of my Diamond-cut.com.au secton?
'However we must always remember that excessive brilliance will drown out potential fire.'

Try this experiment - sit diamond still on desk / table, with one or a few strong small point lights (eg halogen in ceiling) - sit very still and move until you look at one very strong bright white flash. Now move left and right (or to and away) and you will see the flash tails off to blue one way and red the other way. Move closer and there will be less color - more white. Now move away and there will be more color and less white. Move to the other side of room or stand up on a chair and that flash will have little or no white and you will begin to see the green in the center of the spectrum.

Yes I understand what you are saying. If you add White Light to Red Light you still get white light. At an extreme angle your eye see predominantly the red longest visible spectrum wavelength of light only or the blue shortest wavelength of visible light only, and head on the whole spectrum of colours added together which will appear to be just white light.

Nitpicking - if you beam white and red to intersect, the result will be neither white nor red, even assuming neglig. interference/phase patterning issues.


How I interpret Garry's words: when you disperse light through the prism that is the diamond, the light colour that your pupil(s) see is different as the separated ray's diametre changes based on how far from the surface you are... up close and personal you're most probably looking at the beam with one eye, but you're close enough that your pupil can encompass the whole spectrum so you see white. Move a little further away, with one eye, you'll start to see colour as you shift.. open both eyes and you will once again see white - or the visual cortex interprets white, anyway. Keep moving, and at some distance even with both eyes you'll see only whatever wavelength you happen to be standing in front of..perhaps, find a big diamond and orient it so you get a strong enough coherent red emission, you could stick that infamous opaque disc in front of it and see the bright dot the other side

and wouldn't that baffle your buyers!

It's for much the same reason that you see more colour when you're standing in front of a mirror, then - the dispersed wavelengths are incident on the mirror at (albeit slightly) different angles so the results of the dispersion are even more drastic upon reflection.

 

[yssie]

Another question:



A small EC may have the same size virtual facets as a large RB. Why, then, do ECs of all sizes exhibit that characteristic bold flash while the RB would be twinkly?

Is that even a true statement, or would they be comparable?

 

[whatmeworry]

My guess is the two fold symmetry of EC make it more on-off and the eight-fold of RB make it more twinkly.

 

[Karl_K]

Date: 1/28/2010 6:04:35 PM
Author: yssie
Another question:




A small EC may have the same size virtual facets as a large RB. Why, then, do ECs of all sizes exhibit that characteristic bold flash while the RB would be twinkly?


Is that even a true statement, or would they be comparable?

shape of the VF''s and the spaces between flashes.

 

[Garry H (Cut Nut)]

Date: 1/28/2010 2:47:59 AM
Author: yssie

Date: 1/28/2010 1:46:57 AM
Author: ChunkyCushionLover

Date: 1/26/2010 6:00:22 PM
Author: Garry H (Cut Nut)









CCL you are probably referring to this comment at the end of my Diamond-cut.com.au secton?
''However we must always remember that excessive brilliance will drown out potential fire.''

Try this experiment - sit diamond still on desk / table, with one or a few strong small point lights (eg halogen in ceiling) - sit very still and move until you look at one very strong bright white flash. Now move left and right (or to and away) and you will see the flash tails off to blue one way and red the other way. Move closer and there will be less color - more white. Now move away and there will be more color and less white. Move to the other side of room or stand up on a chair and that flash will have little or no white and you will begin to see the green in the center of the spectrum.

Yes I understand what you are saying. If you add White Light to Red Light you still get white light. At an extreme angle your eye see predominantly the red longest visible spectrum wavelength of light only or the blue shortest wavelength of visible light only, and head on the whole spectrum of colours added together which will appear to be just white light.

Nitpicking - if you beam white and red to intersect, the result will be neither white nor red, even assuming neglig. interference/phase patterning issues.


How I interpret Garry''s words: when you disperse light through the prism that is the diamond, the light colour that your pupil(s) see is different as the separated ray''s diametre changes based on how far from the surface you are... up close and personal you''re most probably looking at the beam with one eye, but you''re close enough that your pupil can encompass the whole spectrum so you see white. Move a little further away, with one eye, you''ll start to see colour as you shift.. open both eyes and you will once again see white - or the visual cortex interprets white, anyway. Keep moving, and at some distance even with both eyes you''ll see only whatever wavelength you happen to be standing in front of..perhaps, find a big diamond and orient it so you get a strong enough coherent red emission, you could stick that infamous opaque disc in front of it and see the bright dot the other side

and wouldn''t that baffle your buyers!

It''s for much the same reason that you see more colour when you''re standing in front of a mirror, then - the dispersed wavelengths are incident on the mirror at (albeit slightly) different angles so the results of the dispersion are even more drastic upon reflection.

Correct yssie, except that no single flash from less than a 1,000ct diamond is larg enough to seen by both eyes.
The limitation is the size of the pupil which as you know is wider in dim light which is a partial reason for their being more fire seen in dim lighting.

Also mixing a red with full spectrum white would might not make a lot of difference - but is probably impossible anyway because the light would need to come from the same facet and therefore from the same light source

 

[Garry H (Cut Nut)]

Date: 1/28/2010 6:04:35 PM
Author: yssie
Another question:



A small EC may have the same size virtual facets as a large RB. Why, then, do ECs of all sizes exhibit that characteristic bold flash while the RB would be twinkly?

Is that even a true statement, or would they be comparable?

Yes WMW, but maybe also that the same long virtual facet when moved in a direction where it is still lined up with the light source, especially if that was a big or long one like a flouro tube, would not flash at all for a fair range of movement.

 

[yssie]

Date: 1/29/2010 11:51:16 PM
Author: Garry H (Cut Nut)

Date: 1/28/2010 6:04:35 PM
Author: yssie
Another question:



A small EC may have the same size virtual facets as a large RB. Why, then, do ECs of all sizes exhibit that characteristic bold flash while the RB would be twinkly?

Is that even a true statement, or would they be comparable?

Yes WMW, but maybe also that the same long virtual facet when moved in a direction where it is still lined up with the light source, especially if that was a big or long one like a flouro tube, would not flash at all for a fair range of movement.

Huh.


I didn''t think about what would be needed to create the flash in the first place.



Thanks, Garry!

 

[Garry H (Cut Nut)]

Yussi run this program - it may only work via explorer - Sergey and Yuri put it up more than 10 years ago and it is amazing
http://www.cutstudy.com/cut/english/comp/scint1.htm

It is a beam of light shining perp to the table and the flashes and fire are what you would see on an imaginary screen about 12 inches from the diamond.
Change the proportions or move the diamond.
GIA did the same thing in software they never managed to use that was flawed becuse it showed green flashes, which you can imagine from our conversation here - being in the middle of the spectrum - they are very very rare to be seen.
This software is free!

 

[Garry H (Cut Nut)]

Especially see this page
http://www.gemology.ru/cut/english/grading1/4.htm