When do we get fire? Why is it sometimes pastel?

[Rockdiamond]

Serg, all of the definitions you have used are exactly why the term "performance" when used in regard to the way a diamond handles light, is opinion. The word is being abused. It's being used incorrectly.
Actually the use of the word "performance" in relation to the way a diamond handles light is more than opinion. It's a sales pitch, pure and simple.
If a website want to claim their diamonds "have better performance" they have the right to do so. Just like Ford can say their cars are "zippier".
But if that claim gets repeated here, in an environment that is supposed to be free of sales pitches, it needs to be examined.
Earlier in this thread someone said that "Ideal optics" are why a person's diamond exhibited fire.
That's not the case- as we've already discussed, a larger diamond, not as well cut will produce more fire than a smaller stone with "Ideal Optics"

Every test of light going through a diamond is based on certain suppositions.
You'd have to do that to test effectively- in a scientific manner.
For example- the light needs to be a consistent color, and brightness.
It needs to be coming from a certain direction. The diamond needs to be oriented in a specified position in regards to the light.
But in the real world, different rules apply.
People rarely if ever look at their diamonds in a scientifically controlled environment.
They never show off their diamonds in a scientific manner.
For this reason, making claims of "performance" without identifying what the basis of the claim is is misleading.

 

[Rockdiamond]

Fire in a FCD ( Actually a Y-Z color)

 

[Garry H (Cut Nut)]

Serg, all of the definitions you have used are exactly why the term "performance" when used in regard to the way a diamond handles light, is opinion. The word is being abused. It's being used incorrectly.
Actually the use of the word "performance" in relation to the way a diamond handles light is more than opinion. It's a sales pitch, pure and simple.
If a website want to claim their diamonds "have better performance" they have the right to do so. Just like Ford can say their cars are "zippier".
But if that claim gets repeated here, in an environment that is supposed to be free of sales pitches, it needs to be examined.
Earlier in this thread someone said that "Ideal optics" are why a person's diamond exhibited fire.
That's not the case- as we've already discussed, a larger diamond, not as well cut will produce more fire than a smaller stone with "Ideal Optics"

Every test of light going through a diamond is based on certain suppositions.
You'd have to do that to test effectively- in a scientific manner.
For example- the light needs to be a consistent color, and brightness.
It needs to be coming from a certain direction. The diamond needs to be oriented in a specified position in regards to the light.
But in the real world, different rules apply.
People rarely if ever look at their diamonds in a scientifically controlled environment.
They never show off their diamonds in a scientific manner.
For this reason, making claims of "performance" without identifying what the basis of the claim is is misleading.

David would you consider the lighting in your ViBox to be capable of providing real world lighting? If you do then I can assure you that it is possible to control that lighting and make a scientifically controlled environment.

 

[Garry H (Cut Nut)]

Serg, all of the definitions you have used are exactly why the term "performance" when used in regard to the way a diamond handles light, is opinion. The word is being abused. It's being used incorrectly.
Actually the use of the word "performance" in relation to the way a diamond handles light is more than opinion. It's a sales pitch, pure and simple.
If a website want to claim their diamonds "have better performance" they have the right to do so. Just like Ford can say their cars are "zippier".
But if that claim gets repeated here, in an environment that is supposed to be free of sales pitches, it needs to be examined.
Earlier in this thread someone said that "Ideal optics" are why a person's diamond exhibited fire.
That's not the case- as we've already discussed, a larger diamond, not as well cut will produce more fire than a smaller stone with "Ideal Optics"

Every test of light going through a diamond is based on certain suppositions.
You'd have to do that to test effectively- in a scientific manner.
For example- the light needs to be a consistent color, and brightness.
It needs to be coming from a certain direction. The diamond needs to be oriented in a specified position in regards to the light.
But in the real world, different rules apply.
People rarely if ever look at their diamonds in a scientifically controlled environment.
They never show off their diamonds in a scientific manner.
For this reason, making claims of "performance" without identifying what the basis of the claim is is misleading.

Read page 117 and part of 118 http://www.gem.org.au/ckfinder/userfiles/files/GAA_Journal_V25_No3_web2(1).pdf
There are lots of pictures, so it will not take long

 

[Serg]

Serg, all of the definitions you have used are exactly why the term "performance" when used in regard to the way a diamond handles light, is opinion. The word is being abused. It's being used incorrectly.
Actually the use of the word "performance" in relation to the way a diamond handles light is more than opinion. It's a sales pitch, pure and simple.
If a website want to claim their diamonds "have better performance" they have the right to do so. Just like Ford can say their cars are "zippier".
But if that claim gets repeated here, in an environment that is supposed to be free of sales pitches, it needs to be examined.
Earlier in this thread someone said that "Ideal optics" are why a person's diamond exhibited fire.
That's not the case- as we've already discussed, a larger diamond, not as well cut will produce more fire than a smaller stone with "Ideal Optics"

Every test of light going through a diamond is based on certain suppositions.
You'd have to do that to test effectively- in a scientific manner.
For example- the light needs to be a consistent color, and brightness.
It needs to be coming from a certain direction. The diamond needs to be oriented in a specified position in regards to the light.
But in the real world, different rules apply.
People rarely if ever look at their diamonds in a scientifically controlled environment.
They never show off their diamonds in a scientific manner.
For this reason, making claims of "performance" without identifying what the basis of the claim is is misleading.

David, I am disagree with you.

People( Consumers) rarely( may be never) measure power of engine in them cars. But it does not mean that cars have not performance and that it is not possible to measure engine in horsepowers , ...

It is not misleading to speak about car performance, same about diamonds. we need just define the system for measurements.
but even if we can not measure performance , we may compare diamonds by performance .
for example consumers can not measure speed with high accuracy, but they can easy see which car is faster.

 

[Rockdiamond]

Just curious Karl, what is your favorite place or type of lighting to see fire?
If you never noticed, my avatar- cut by Yoram, actually exhibits fire in the table and on the crown in spite of such a deep color. Which is another aspect never touched- how color affects fire.
I notice it all the time in pictures.

My favourite place to see fire is under the huge plane (plain) tree beside the shop on a cloudy but bright day.
The spaces between the leaves create thousands of tiny pin points of light and diamond dance. In this case a better cut definitely produces more fire.
I am on a trip at present and only catching up with this, but David I believe you read the article that Sergey, Yuri, Janak and I wrote for the Australian Gemmologist? http://www.gem.org.au/ckfinder/userfiles/files/GAA_Journal_V25_No3_web2(1).pdf There are sections and definitions of fire.

If not- surely you read the short summary in Rapaport magazine a few months ago. http://www.rapnet.com/News/NewsItem...IssueID=0&ArticleTitle=Vision+Impacts+Sparkle

Fire is like BHP, or torque, or standing 1/4 mile time. It can be measured, which is exactly what Sergey's team of developers are working on using ViBox as the capture device. This is also importantly done with the stereo capture system - because as you should aall do to test it - see how many flashes you see with one eye vs with two. Most cuts give nearly twice as many with two eyes because the direction of viewing means you see fire from different light sources. Occasionally where fire should be the other eye sees a really bright source from the same virtual facet and that swamps the fire flash and we percieve only the white flash.

DF - that green flash is very rare and very hard to see - amaxing photo!

Hi Garry- We're going to have to agree to disagree on this point.
If Ford was using a totally different environment ( like a special sticky track) to run the 1/4 mile- or putting on different tires or other equipment to get better numbers- that would render those performance results irrelevant to consumers.
Same thing here.
Not to take anything away from your research. The Vibox is one of the most amazing inventions I've ever seen- remarkable.
But claiming superior performance due to fire which can be induced in the Vibox is a sales tool.
If a consumer has a ViBox, then they can replicate the results. Otherwise, any measurement of fire in a controlled environment is not necessarily useful for people wanting to buy well cut diamonds. After all, different settings in the Vibox produce different amounts of fire- which again proves my point. Changing settings in the environment change performance ( as the term is being used in this case).
For example, we need to use different settings in ViBox for colorless diamonds, and FCDs. Then with FCD's different colors require different settings to produce accurate results. So in the case of Vibox- surely the most advanced system developed to date for taking pictures of diamonds, operator settings make a big difference in how the picture looks. This is actually an asset for us- as we are control freaks

 

[Rockdiamond]

Serg, all of the definitions you have used are exactly why the term "performance" when used in regard to the way a diamond handles light, is opinion. The word is being abused. It's being used incorrectly.
Actually the use of the word "performance" in relation to the way a diamond handles light is more than opinion. It's a sales pitch, pure and simple.
If a website want to claim their diamonds "have better performance" they have the right to do so. Just like Ford can say their cars are "zippier".
But if that claim gets repeated here, in an environment that is supposed to be free of sales pitches, it needs to be examined.
Earlier in this thread someone said that "Ideal optics" are why a person's diamond exhibited fire.
That's not the case- as we've already discussed, a larger diamond, not as well cut will produce more fire than a smaller stone with "Ideal Optics"

Every test of light going through a diamond is based on certain suppositions.
You'd have to do that to test effectively- in a scientific manner.
For example- the light needs to be a consistent color, and brightness.
It needs to be coming from a certain direction. The diamond needs to be oriented in a specified position in regards to the light.
But in the real world, different rules apply.
People rarely if ever look at their diamonds in a scientifically controlled environment.
They never show off their diamonds in a scientific manner.
For this reason, making claims of "performance" without identifying what the basis of the claim is is misleading.

David, I am disagree with you.

People( Consumers) rarely( may be never) measure power of engine in them cars. But it does not mean that cars have not performance and that it is not possible to measure engine in horsepowers , ...

It is not misleading to speak about car performance, same about diamonds. we need just define the system for measurements.
but even if we can not measure performance , we may compare diamonds by performance .
for example consumers can not measure speed with high accuracy, but they can easy see which car is faster.

Serg- please take a test drive in a Porsche 911
Then drive the "S" model.
The difference is immediately noticeable.
It's another 50 BHP under your right foot. Feels really good, let me tell you.

If we're talking about immediately noticeable aspects of diamonds, the main one that comes to mind is spread- a number which can be repeatably measured, regardless of environment. In other words, spread is an objective measurement.
Sparkle, fire, scintillation, liveliness, and any other description of how a diamond handles light is subjective. This is based on the far more intricate manner of light, and it's movement. Far more difficult to measure light movig through a diamond as compared to a car moving down a racetrack.
Then beyond measurement we have human perception.
Anyone driving the S model after a standard 911 will immediately notice the difference in a quantifiable manner ( yes, that S model is faster)
But different manners of light moving through a diamond will not be seen equally by different observers.

 

[Serg]

Just curious Karl, what is your favorite place or type of lighting to see fire?
If you never noticed, my avatar- cut by Yoram, actually exhibits fire in the table and on the crown in spite of such a deep color. Which is another aspect never touched- how color affects fire.
I notice it all the time in pictures.

My favourite place to see fire is under the huge plane (plain) tree beside the shop on a cloudy but bright day.
The spaces between the leaves create thousands of tiny pin points of light and diamond dance. In this case a better cut definitely produces more fire.
I am on a trip at present and only catching up with this, but David I believe you read the article that Sergey, Yuri, Janak and I wrote for the Australian Gemmologist? http://www.gem.org.au/ckfinder/userfiles/files/GAA_Journal_V25_No3_web2(1).pdf There are sections and definitions of fire.

If not- surely you read the short summary in Rapaport magazine a few months ago. http://www.rapnet.com/News/NewsItem...IssueID=0&ArticleTitle=Vision+Impacts+Sparkle

Fire is like BHP, or torque, or standing 1/4 mile time. It can be measured, which is exactly what Sergey's team of developers are working on using ViBox as the capture device. This is also importantly done with the stereo capture system - because as you should aall do to test it - see how many flashes you see with one eye vs with two. Most cuts give nearly twice as many with two eyes because the direction of viewing means you see fire from different light sources. Occasionally where fire should be the other eye sees a really bright source from the same virtual facet and that swamps the fire flash and we percieve only the white flash.

DF - that green flash is very rare and very hard to see - amaxing photo!

Hi Garry- We're going to have to agree to disagree on this point.
If Ford was using a totally different environment ( like a special sticky track) to run the 1/4 mile- or putting on different tires or other equipment to get better numbers- that would render those performance results irrelevant to consumers.
Same thing here.
Not to take anything away from your research. The Vibox is one of the most amazing inventions I've ever seen- remarkable.
But claiming superior performance due to fire which can be induced in the Vibox is a sales tool.
If a consumer has a ViBox, then they can replicate the results. Otherwise, any measurement of fire in a controlled environment is not necessarily useful for people wanting to buy well cut diamonds. After all, different settings in the Vibox produce different amounts of fire- which again proves my point. Changing settings in the environment change performance ( as the term is being used in this case).
For example, we need to use different settings in ViBox for colorless diamonds, and FCDs. Then with FCD's different colors require different settings to produce accurate results. So in the case of Vibox- surely the most advanced system developed to date for taking pictures of diamonds, operator settings make a big difference in how the picture looks. This is actually an asset for us- as we are control freaks

1) Changing settings do not change diamond performance. It changes Fire but it does not change Performance.
Same for Cars. Weather is change speed during race. One car wins during sun race, other in raining . But rain does not change engine power.
2) Do you use Vibox colour profiles. You do not need change settings to receive correct colour for colourless and fancy colour diamonds if you use only internal TOP Vibox light and correct colour profiles. If you change setting then you have wrong colour .

 

[Rockdiamond]

Serg- maybe we need to agree that our differences on this issue to a language issue.
If fire changes, how does performance not change, unless we're speaking of theoretical performance?
And if we are speaking of theoretical performance, it should be identified that way- as opposed to some sort of advertising statement.

 

[Serg]

Serg, all of the definitions you have used are exactly why the term "performance" when used in regard to the way a diamond handles light, is opinion. The word is being abused. It's being used incorrectly.
Actually the use of the word "performance" in relation to the way a diamond handles light is more than opinion. It's a sales pitch, pure and simple.
If a website want to claim their diamonds "have better performance" they have the right to do so. Just like Ford can say their cars are "zippier".
But if that claim gets repeated here, in an environment that is supposed to be free of sales pitches, it needs to be examined.
Earlier in this thread someone said that "Ideal optics" are why a person's diamond exhibited fire.
That's not the case- as we've already discussed, a larger diamond, not as well cut will produce more fire than a smaller stone with "Ideal Optics"

Every test of light going through a diamond is based on certain suppositions.
You'd have to do that to test effectively- in a scientific manner.
For example- the light needs to be a consistent color, and brightness.
It needs to be coming from a certain direction. The diamond needs to be oriented in a specified position in regards to the light.
But in the real world, different rules apply.
People rarely if ever look at their diamonds in a scientifically controlled environment.
They never show off their diamonds in a scientific manner.
For this reason, making claims of "performance" without identifying what the basis of the claim is is misleading.

David, I am disagree with you.

People( Consumers) rarely( may be never) measure power of engine in them cars. But it does not mean that cars have not performance and that it is not possible to measure engine in horsepowers , ...

It is not misleading to speak about car performance, same about diamonds. we need just define the system for measurements.
but even if we can not measure performance , we may compare diamonds by performance .
for example consumers can not measure speed with high accuracy, but they can easy see which car is faster.

Serg- please take a test drive in a Porsche 911
Then drive the "S" model.
The difference is immediately noticeable.
It's another 50 BHP under your right foot. Feels really good, let me tell you.

If we're talking about immediately noticeable aspects of diamonds, the main one that comes to mind is spread- a number which can be repeatably measured, regardless of environment. In other words, spread is an objective measurement.
Sparkle, fire, scintillation, liveliness, and any other description of how a diamond handles light is subjective. This is based on the far more intricate manner of light, and it's movement. Far more difficult to measure light movig through a diamond as compared to a car moving down a racetrack.
Then beyond measurement we have human perception.
Anyone driving the S model after a standard 911 will immediately notice the difference in a quantifiable manner ( yes, that S model is faster)
But different manners of light moving through a diamond will not be seen equally by different observers.

David,
Bingo, Exactly same for diamonds.
You have to compare different cuts in same light environments , as you compared Porsches in same conditions .

You do not need measure horsepower to feel big difference in Porsches performance , same for diamonds.
if you have opportunity for test drive you do not need numbers. If you can not do test drive( or it is very costly) then you need numbers.
Numbers are important for pre-selection, ( it is just fastest and cheapest way to receive your shortlist) then you need test drive in adequate conditions ( and same for both cars, diamonds,,)
all what you do to select best for you car you may do to select best for you diamond. And diamond industry have to creates such conditions for consumer "Diamond test drive" or diamond market will continuously shrinking .

 

[Serg]

Serg- maybe we need to agree that our differences on this issue to a language issue.
If fire changes, how does performance not change, unless we're speaking of theoretical performance?
And if we are speaking of theoretical performance, it should be identified that way- as opposed to some sort of advertising statement.

each mirror has reflective coefficient . Some has 99%, some has 90%. this coefficient does not depend from light source.

you will see mirror differently in different light conditions but light conditions does not mirror performance , mirror reflective coefficient .
and reflective coefficient is not theoretical performance.

you do not need know what mirror has higher reflective coefficient to compare two mirrors. you can compare mirror performance in any light conditions except in darkness.

to compare fire performance you need compare diamonds in different light environments. but Idea is same. If you can not measure yet then try to compare in same conditions.

 

[Rockdiamond]

Serg, if 50 people drive both cars, we'll have 100% agreement on which performs better- if the characteristic of performance we are looking at is power.
If 50 people compare two diamonds with different levels of performance ( meaning "performance" as you, or whoever else wants to claim a calibration for diamond performance defines the word), we're not going to have anywhere near the level of agreement.
Even if all the observers could agree on what the terms mean exactly ( scintillation, fire, brilliance, etc) different observers will have different impressions.
But we can't even get to that point because not all people see "brilliance" in the same manner.

This is a very interesting discussion- and the part about what the diamond industry can do is probably at the crux of it.
Personally, I don't feel that standardization is going to lead to industry growth- but who knows. What we do know is that things are changing- and the Vibox is certainly going to influence the future of the diamond business- I'm sure we agree on that.

 

[Rockdiamond]

Serg- maybe we need to agree that our differences on this issue to a language issue.
If fire changes, how does performance not change, unless we're speaking of theoretical performance?
And if we are speaking of theoretical performance, it should be identified that way- as opposed to some sort of advertising statement.

each mirror has reflective coefficient . Some has 99%, some has 90%. this coefficient does not depend from light source.

you will see mirror differently in different light conditions but light conditions does not mirror performance , mirror reflective coefficient .
and reflective coefficient is not theoretical performance.

you do not need know what mirror has higher reflective coefficient to compare two mirrors. you can compare mirror performance in any light conditions except in darkness.

to compare fire performance you need compare diamonds in different light environments. but Idea is same. If you can not measure yet then try to compare in same conditions.

Serg- we'd need to test two mirrors aimed at each other to make this a meaningful comparison to a diamond.
And as I'm sure you know better than anyone, when we increase the variables, drawing meaningful conclusions becomes exponentially more difficult.
The position of the two mirrors to each other, then to the lighting source will produce an infinite amount of variations- as opposed to one mirror, with one light.

 

[Serg]

Serg, if 50 people drive both cars, we'll have 100% agreement on which performs better- if the characteristic of performance we are looking at is power.
If 50 people compare two diamonds with different levels of performance ( meaning "performance" as you, or whoever else wants to claim a calibration for diamond performance defines the word), we're not going to have anywhere near the level of agreement.
Even if all the observers could agree on what the terms mean exactly ( scintillation, fire, brilliance, etc) different observers will have different impressions.
But we can't even get to that point because not all people see "brilliance" in the same manner.

This is a very interesting discussion- and the part about what the diamond industry can do is probably at the crux of it.
Personally, I don't feel that standardization is going to lead to industry growth- but who knows. What we do know is that things are changing- and the Vibox is certainly going to influence the future of the diamond business- I'm sure we agree on that.

David,

100%( may be 90%) people will agree with cars performance difference only if cars have similar mass but big difference in BHP (AND they compared cars in same race conditions)
if difference in BHP just 5 BHP or cars have big difference in mass or they drove it in different race conditions then you will not receive good consistancy in answers.
same for diamonds.

usually people( consumers and trades) have not ability to compare two diamonds in same "race conditions". it is exact reason why we develop Vibox. 5 years ago we had not ability to check our ideas just because it was not possible to check 2 diamonds in exactly same Fire conditions.

 

[Rockdiamond]

We are in total agreement that the Vibox is amazing
But it seems we will never come to an agreement on what "diamond performance" is- or how it relates to a consumer buying a diamond.

 

[Serg]

Serg- maybe we need to agree that our differences on this issue to a language issue.
If fire changes, how does performance not change, unless we're speaking of theoretical performance?
And if we are speaking of theoretical performance, it should be identified that way- as opposed to some sort of advertising statement.

each mirror has reflective coefficient . Some has 99%, some has 90%. this coefficient does not depend from light source.

you will see mirror differently in different light conditions but light conditions does not mirror performance , mirror reflective coefficient .
and reflective coefficient is not theoretical performance.

you do not need know what mirror has higher reflective coefficient to compare two mirrors. you can compare mirror performance in any light conditions except in darkness.

to compare fire performance you need compare diamonds in different light environments. but Idea is same. If you can not measure yet then try to compare in same conditions.

Serg- we'd need to test two mirrors aimed at each other to make this a meaningful comparison to a diamond.
And as I'm sure you know better than anyone, when we increase the variables, drawing meaningful conclusions becomes exponentially more difficult.
The position of the two mirrors to each other, then to the lighting source will produce an infinite amount of variations- as opposed to one mirror, with one light.

David ,
Put mirrors in to Vibox, one by one. Do not change any settings, take movies.
it is enough to compare reflective index with very high level accuracy . but only One by one( do not put them together into Vibox, one to each other)

 

[Dancing Fire]

[quote="Garry H (Cut Nut)|

DF - that green flash is very rare and very hard to see - amaxing photo!

Garry...Why is the green flash rare?..

Usually that part of the flash turns white/bright
See figure 3.5 in this article DF, and you will understtand, then try some real life experiments with a steady hand and few good for fire point lightsources.
http://www.gem.org.au/ckfinder/userfiles/files/GAA_Journal_V25_No3_web2(1).pdf

(David will not be able to do this in his office)[/quote]
Thanks Garry

 

[Serg]

[quote="Garry H (Cut Nut)|

DF - that green flash is very rare and very hard to see - amaxing photo!

Garry...Why is the green flash rare?..

Usually that part of the flash turns white/bright
See figure 3.5 in this article DF, and you will understtand, then try some real life experiments with a steady hand and few good for fire point lightsources.
http://www.gem.org.au/ckfinder/userfiles/files/GAA_Journal_V25_No3_web2(1).pdf

(David will not be able to do this in his office)

Thanks Garry[/quote]

Take 3 flashlights :blue, green, red.
direct it in one point, you see white cycle. then move blue flashlight in left direction , red flashlight in right direction on same shift.
if shift is less that radius of light spot then you will see white in central part. if shift is bugger than flashlight spot radius than you see green in central part.
the shift is value of angular dispersion. spot radius is light source angular size.
usually diamond cut angular dispersion is less than angular size of most typical lights sources

 

[Dancing Fire]

Serg...I don't have the 3 colored flashlights..

 

[Serg]

Serg...I don't have the 3 colored flashlights..

it is easy to buy now.( colour LED's, or use colour filters with white flashlights)
they are much more cheaper than diamonds and more handy .

 

[Dancing Fire]

[quote="Rockdiamond|


DF- I did not notice the answer to my question. Have you seen what we are referring to ( fire= dispersion of color) with your naked eyes?
To remind you- I began learning about diamonds and was trained by Harry Winston to assess diamonds for cut, color, and clarity- in fact, I'm looking forward to the 40th anniversary of my start date at Winston in about 10 days. The amount I've leaned and seen over these 40 years is astounding.
I've always LOVED well cut stones, and have been lucky enough to see countless sparkly diamonds- even luckier to have owned thousands of amazing, sparkling diamonds.[/quote]


David
After all these years on PS I still don't know what do you refer as "well cut" stones. wish I can read your mind.

 

[Rockdiamond]

David
After all these years on PS I still don't know what do you refer as "well cut" stones. wish I can read your mind.

I am totally disappointed DF_ I was told you could read minds
Here's an example of a well cut stone


Karl, what are we having for dinner?- I have NO food allergies, so the sky's the limit

 

[Dancing Fire]

David
After all these years on PS I still don't know what do you refer as "well cut" stones. wish I can read your mind.

I am totally disappointed DF_ I was told you could read minds
Here's an example of a well cut stone


Karl, what are we having for dinner?- I have NO food allergies, so the sky's the limit

Royal Asscher?

 

[Rockdiamond]

No, actually it is a very well cut generic DF
I love a Asschers - and Octavias, like yours

 

[Garry H (Cut Nut)]

[quote="Garry H (Cut Nut)|

DF - that green flash is very rare and very hard to see - amaxing photo!

Garry...Why is the green flash rare?..

Usually that part of the flash turns white/bright
See figure 3.5 in this article DF, and you will understtand, then try some real life experiments with a steady hand and few good for fire point lightsources.
http://www.gem.org.au/ckfinder/userfiles/files/GAA_Journal_V25_No3_web2(1).pdf

(David will not be able to do this in his office)

Thanks Garry

Take 3 flashlights :blue, green, red.
direct it in one point, you see white cycle. then move blue flashlight in left direction , red flashlight in right direction on same shift.
if shift is less that radius of light spot then you will see white in central part. if shift is bugger than flashlight spot radius than you see green in central part.
the shift is value of angular dispersion. spot radius is light source angular size.
usually diamond cut angular dispersion is less than angular size of most typical lights sources[/quote]

I tried a few electronics shops and online - i can buy expensive filters, but did not find cheap led flashlight / torches Sergey?

 

[Karl_K]

I tried a few electronics shops and online - i can buy expensive filters, but did not find cheap led flashlight / torches Sergey?

Not expensive but not really what I would consider cheap either:
http://www.amazon.com/Alldaymall-F-497-Wf-502B-Hunting-Flashlight/dp/B008YQDEFK/ref=sr_1_1?s=hi&ie=UTF8&qid=1421042733&sr=1-1

http://www.amazon.com/Alldaymall-F-497-Wf-502B-Hunting-Flashlight/dp/B008YQDEFK/ref=sr_1_1?s=hi&ie=UTF8&qid=1421042733&sr=1-1

plus another $17 for batteries and a charger.
http://www.amazon.com/EBL%C2%AE-2600mAh-Rechargeable-Battery-Universal/dp/B00DNPT19K/ref=sr_1_20?ie=UTF8&qid=1421043498&sr=8-20&keywords=18650

 

[Serg]

Garry,

http://www.amazon.com/Gerber-22-80016-Recon-White-Flashlight/dp/B0006TU75I

Flash light with cheap filters. also there are many LED blue, red , green flashlights available
http://www.amazon.com/gp/product/B0..._m=ATVPDKIKX0DER&pf_rd_r=17SC17DZJ9GANXGNRPFG
http://www.amazon.com/s/ref=nb_sb_s...ight&sprefix=blue+led+flashlight,sporting,259

just check in Amazon

 

[Garry H (Cut Nut)]

http://vod.ebay.com.au/vod/FetchOrderDetails?ViewPaymentStatus&transId=1073446837004&itemId=141360293377&qu=4&ssPageName=ADME:L:OC:AU:1503
these were about $7 each - cree led's and i got a UV one as well
but free shipping will take +2 weeks