yellow diamonds and fire

[Cehrabehra]

Yes, I''ve done the searches LOL But I can''t find anything about what sort of fire yellow diamonds have... do they refract full spectrum the way near colorless do? When they reflect light off their table etc does it stay white or does it always come back yellow? Also... if you *want* to see a difference between stones, how many color grades apart do they need to be?

 

[Daniel B]

hmmm, good question, i''d like to hear the answer to this, too

 

[Madam Bijoux]

Hi! I have a fancy yellow radiant, and I always see the full spectrum. The light from the table is yellow.

 

[maxspinel]

Date: 9/4/2006 11:35:32 PM
Author:Cehrabehra
Yes, I''ve done the searches LOL But I can''t find anything about what sort of fire yellow diamonds have... do they refract full spectrum the way near colorless do? When they reflect light off their table etc does it stay white or does it always come back yellow? Also... if you *want* to see a difference between stones, how many color grades apart do they need to be?

I am hoping that some experts will help out in this question. I am just a consumer who happens to own a yellow diamond. I guess yellow diamond is a diamond with yellow as the body color but it should possess all the refractive properties of a diamond. When light hits a stone, some of the spectrum is being absorbed and the remaining reflected back to the eye and that define the color of the stone. So my inclination is the absorption charactertistics of the white diamonds will be slightly different than that of a yellow diamond. However, that being said, it also possess the diamond''s characteristics to be able to disperse the light so we should be able to see a full spectrum minus those that gets absorbed. A lighter stone should look more brilliant than a deep colored one.

There are different levels of intensity in yellow diamonds. GIA white color Grade L, M, N, .... will look tinted, then color goes to very light, then light in the x,y,z range. After that it will be GIA color diamond grade fancy light, fancy, fancy intense, fancy vivid, fancy deep. I am not sure which intensity are you interested in? The very light, light yellow (cape) diamonds are very bright looking stones if you like the subtle color. However, one needs to get to the fancy light or fancy range to really appreciate the more distinguishing yellow color. Yellow is a very bright color and it really stands out with the white diamond side stones or halo pave. I''ve always thought that yellow diamonds is a bargin compared to white diamonds. With the same price, why get a tinted one instead of a real yellow one and the yellow diamonds are so much rarer.

 

[Cehrabehra]

Date: 9/5/2006 4:23:43 PM
Author: maxspinel

I am hoping that some experts will help out in this question. I am just a consumer who happens to own a yellow diamond. I guess yellow diamond is a diamond with yellow as the body color but it should possess all the refractive properties of a diamond. When light hits a stone, some of the spectrum is being absorbed and the remaining reflected back to the eye and that define the color of the stone. So my inclination is the absorption charactertistics of the white diamonds will be slightly different than that of a yellow diamond. However, that being said, it also possess the diamond''s characteristics to be able to disperse the light so we should be able to see a full spectrum minus those that gets absorbed. A lighter stone should look more brilliant than a deep colored one.

There are different levels of intensity in yellow diamonds. GIA white color Grade L, M, N, .... will look tinted, then color goes to very light, then light in the x,y,z range. After that it will be GIA color diamond grade fancy light, fancy, fancy intense, fancy vivid, fancy deep. I am not sure which intensity are you interested in? The very light, light yellow (cape) diamonds are very bright looking stones if you like the subtle color. However, one needs to get to the fancy light or fancy range to really appreciate the more distinguishing yellow color. Yellow is a very bright color and it really stands out with the white diamond side stones or halo pave. I''ve always thought that yellow diamonds is a bargin compared to white diamonds. With the same price, why get a tinted one instead of a real yellow one and the yellow diamonds are so much rarer.

For a RHR there are a lot of things I''d do that I wouldn''t for a LHR. Color kinda scares me for a ring I''ll wear 24/7. I''m weird about things matching or at least being neutral. I''ve pretty much decided I need one of every color stone eventually but for my LHR if I were to go yellow it would have to be pretty light... now I *do* like the warm stones... J and K for sure, pretty sure I''d like L & M as well. But I''m wondering... if I *wanted* there to be contrast but yet not have a super yellow stone... would getting an "M" stone and putting it with "H" stones bring enough contrast for it to look intentional or would it just look weirdly off?

Thanks for the info on the refraction! It''s hard for me to picture it... in my head the yellow tints the other colors so you mostly see orange and yellow and green... hard to picture purple coming off of it but it must be really spectacular!

 

[kenny]

If a piece of glass had no color it would pass all colors equally.

A red piece will pass red the best and attenuate all other colors to some degree.
It will attenuate green, red's compliment, the most.

A violet piece will pass violet the best and attenuate all other colors to some degree.
It will attenuate yellow, violet's compliment, the most.

A yellow piece will pass yellow the best and attenuate all other colors to some degree.
It will attenuate violet, yellow's compliment, the most.

Now whether the attenuation of 1/4 of an inch of yellow diamond offers to violet light enough to detect with the human eye I don't know, but in theory a yellow diamond must attenuate violet more than any other color.

So I'd say the fire, or flashes of color, of a yellow diamond will contain a little less violet.
Whether it is noticeable I cannot say.

This is based on my understanding of light and color theory.
Please correct me if I'm wrong.

 

[Cehrabehra]

Date: 9/5/2006 11:53:52 PM
Author: kenny
If a piece of glass had no color it would pass all colors equally.

A red piece will pass red the best and attenuate all other colors to some degree.
It will attenuate green, red''s compliment, the most.

A violet piece will pass violet the best and attenuate all other colors to some degree.
It will attenuate yellow, violet''s compliment, the most.

A yellow piece will pass yellow the best and attenuate all other colors to some degree.
It will attenuate violet, yellow''s compliment, the most.

Now whether the attenuation of 1/4 of an inch of yellow diamond offers to violet light enough to detect with the human eye I don''t know, but in theory a yellow diamond must attenuate violet more than any other color.

So I''d say the fire, or flashes of color, of a yellow diamond will contain a little less violet.
Whether it is noticeable I cannot say.

This is based on my understanding of light and color theory.
Please correct me if I''m wrong.

*though* if you''re looking at a picture of red and blue lines and you put on red glasses, all you see is the blue design... if you have a yellow stone it might be possible you see the extremes of the spectrum but the yellows and oranges and greens just kinda get visually lost in all of the yellow from the stone... the lighter the stone the more I imagine it competes with the yellow... but its possible colors like violet might be more intense because of the contrast... violet and blue/purple. But I don''t know... I was hoping more experts would chime on this... I did several internet searches and found nadasquat.

I know my amethyst isn''t a diamond but it doesn''t do anything but look purple. In my head even if its a yellow diamond, its gonna just look yellow. Madam B says it refracts full spectrum but seriously how well? And for that matter, what about pink and blue diamonds?

 

[oldminer]

The body color of a diamond has a measurable effect on the amount of fire. The measurable amount might be invisible to our eyes and very minute, but it can theoretically be measured.
For this reason, I have often stated that attempting to grade diamond performance with a "fire" metric is a poor strategy.

Fire is very much related to lighting environment. Certain lighting will create more fire and other types of light will diminish fire. The amount of fire also will rise and fall depending on body color.

One chooses a good looking diamond based on other components first. A secondary component is how well fire is seen in the environment you wish to view it in. Every well cut diamond will have sufficient fire in lighting which promotes its occurrence.

 

[Cehrabehra]

Date: 9/6/2006 1:47:21 PM
Author: oldminer
The body color of a diamond has a measurable effect on the amount of fire. The measurable amount might be invisible to our eyes and very minute, but it can theoretically be measured.
For this reason, I have often stated that attempting to grade diamond performance with a ''fire'' metric is a poor strategy.

Fire is very much related to lighting environment. Certain lighting will create more fire and other types of light will diminish fire. The amount of fire also will rise and fall depending on body color.

One chooses a good looking diamond based on other components first. A secondary component is how well fire is seen in the environment you wish to view it in. Every well cut diamond will have sufficient fire in lighting which promotes its occurrence.

the diamond I bought has fire in EVERY light except pitch black... I''ve seen fire by moonlight with this ring - no joke. Sure it''s not leaping out and smacking you the way it does in full sun, it isn''t massaging my eyes the way it does at the grocery store, it isn''t meandering the way it does in diffused... but definitely hitting full spectral even by moonlight...

I have read so much of what you''ve said about how fire is secondary - and I still wonder - to what? Brilliance? brilliance sure is a lot easier to measure that''s for sure, but its importance relative to fire is a matter of opinion.

But seriously - back to my question... if you have a yellow diamond, a Zor light yellow fancy... and you''re outside getting smacked upside the head by its fire, is everything tinted yellow, is it full spectrum?

Also - how many color grades does it take to create enough contrast to look intentional? like say you wanted it to be like DMDMDMDMD would it be enough difference between D and M to look like it was white and off white or yellow or would it just still be so close that it would just look weird and not intentional?

 

[adamasgem]

Date: 9/6/2006 1:47:21 PM
Author: oldminer
The body color of a diamond has a measurable effect on the amount of fire. The measurable amount might be invisible to our eyes and very minute, but it can theoretically be measured.
For this reason, I have often stated that attempting to grade diamond performance with a 'fire' metric is a poor strategy.
I don't know about that Dave.. A fire metric can tell you about the potential to create fire. You are correct that the overall bodycolor will result in the internal absorption of light starting at the blue end of the spectrum, and depending on how the color is concentrated in the diamond, you will get different "fire" results , even though the face up color will appear to be the same. The higher the ooptical symmetry the more broad flash type of fire.

Fire is very much related to lighting environment. And so is any measurement of total light return.

Certain lighting will create more fire and other types of light will diminish fire. The amount of fire also will rise and fall depending on body color.Yup color mixing and internal absorption effect your perception of fire.

One chooses a good looking diamond based on other components first. A secondary component is how well fire is seen in the environment you wish to view it in. Every well cut diamond will have sufficient fire in lighting which promotes its occurrence. Again, just as total light return is subject to lighting environment and spectrum.

This is an old unretouched photo of my Y color master stone in my prototype fire performance scope. The "grey" background you see is actually pure white. The lighting envirionment is about 10000 points sources of white light, so the results aren't aliiased, like if you tried to use the 12 Kittydock(TM) LEDS to show fire. BTW, this color master stone is an OLD AGS 3 cut.
Prooer photos certainly can give you a qualitative idea of the ability to generate fire..

 

[Cehrabehra]

Date: 9/6/2006 6:57:07 PM
Author: adamasgem
This is an old unretouched photo of my Y color master stone in my prototype fire performance scope. The ''grey'' background you see is actually pure white. The lighting envirionment is about 10000 points sources of white light, so the results aren''t aliiased, like if you tried to use the 12 Kittydock(TM) LEDS to show fire. BTW, this color master stone is an OLD AGS 3 cut.
Prooer photos certainly can give you a qualitative idea of the ability to generate fire..

I didn''t really understand anything past "prototype" but that photo is just beautiful!!

 

[adamasgem]

Date: 9/6/2006 8:08:08 PM
Author: Cehrabehra

Date: 9/6/2006 6:57:07 PM
Author: adamasgem
This is an old unretouched photo of my Y color master stone in my prototype fire performance scope. The ''grey'' background you see is actually pure white. The lighting envirionment is about 10000 points sources of white light, so the results aren''t aliiased, like if you tried to use the 12 Kittydock(TM) LEDS to show fire. BTW, this color master stone is an OLD AGS 3 cut.
Prooer photos certainly can give you a qualitative idea of the ability to generate fire..

I didn''t really understand anything past ''prototype'' but that photo is just beautiful!!

Thanks.. We have improved the photo capability considerably and I''m build newer model of the fire performance scope covered in a US patent application, all claims of which have been approved. Minor paperwork and the patent is issued.
The newer setup gives brighter pictures, but even with the original prototype you see the effects of smaller areas of pure hues because of lack of optical symmetry in a stone.

Overall hue, is of course effected by the bodycolor of the stone, but the ability to produce fire is obvious. You can also see dead zones in poorly cut stones. When I get a chance in the next week or so, I''ll dig out some more pics from my other computer that I archived.

One of the things on my table is to correctly model in a foreward raytrace what we can see in the proper envirionment .... DiamondCalc makes a good stab at it, but doesn''t have the capapbility yet, to my knowledge, to model my 10000 point multi source envirionment, however Sergeys new software which I saw at the AGS conclave should do the trick for a reverse ray trace.

 

[maxspinel]

Date: 9/6/2006 6:57:07 PM
Author: adamasgem

Date: 9/6/2006 1:47:21 PM
Author: oldminer
The body color of a diamond has a measurable effect on the amount of fire. The measurable amount might be invisible to our eyes and very minute, but it can theoretically be measured.
For this reason, I have often stated that attempting to grade diamond performance with a ''fire'' metric is a poor strategy.
I don''t know about that Dave.. A fire metric can tell you about the potential to create fire. You are correct that the overall bodycolor will result in the internal absorption of light starting at the blue end of the spectrum, and depending on how the color is concentrated in the diamond, you will get different ''fire'' results , even though the face up color will appear to be the same. The higher the ooptical symmetry the more broad flash type of fire.

Fire is very much related to lighting environment. And so is any measurement of total light return.

Certain lighting will create more fire and other types of light will diminish fire. The amount of fire also will rise and fall depending on body color.Yup color mixing and internal absorption effect your perception of fire.

One chooses a good looking diamond based on other components first. A secondary component is how well fire is seen in the environment you wish to view it in. Every well cut diamond will have sufficient fire in lighting which promotes its occurrence. Again, just as total light return is subject to lighting environment and spectrum.

This is an old unretouched photo of my Y color master stone in my prototype fire performance scope. The ''grey'' background you see is actually pure white. The lighting envirionment is about 10000 points sources of white light, so the results aren''t aliiased, like if you tried to use the 12 Kittydock(TM) LEDS to show fire. BTW, this color master stone is an OLD AGS 3 cut.
Prooer photos certainly can give you a qualitative idea of the ability to generate fire..

I need some clarification on brilliance vs. fire. I thought brilliance is primarily reflection of white light while fire is the separation of the white light into the different color spectrum, similar to the prism effects. Therefore, diamonds cut with smaller tables exhibit more fire while those with larger talbes exhibit more brilliance. A stone can''t achieve optimum fire and brilliance at the same time.

I am trying to understand your attached fire performance image. It is hard to distinguish what is fire vs. brilliance in the picture since the white and color reflection seems to co-mingle. For someone who doesn''t know too much about the technical aspects of the brilliance/fire measurement, I am guessing that the kittydock is some kind of GIA lighting setup which utlizes the LED (light emitting diode??) as sthe source.

Also, for comparison purposes, do you have a similar fire performance scope on a white diamond? This would help to illustrate if there is measurable differences in the fire display (intensity vs. weaker color in some sprectrum). Just like it was stated earlier, the yellowish body color is the result of the absorption of other colors, leaving the yellow as the remaining color to be reflected back to the viewer. However, since the refraction and other properties of diamond remains the same, the light entering the stone will be split into various spectrum color.

 

[maxspinel]

Date: 9/5/2006 9:03:22 PM
Author: Cehrabehra
For a RHR there are a lot of things I''d do that I wouldn''t for a LHR. Color kinda scares me for a ring I''ll wear 24/7. I''m weird about things matching or at least being neutral. I''ve pretty much decided I need one of every color stone eventually but for my LHR if I were to go yellow it would have to be pretty light... now I *do* like the warm stones... J and K for sure, pretty sure I''d like L & M as well. But I''m wondering... if I *wanted* there to be contrast but yet not have a super yellow stone... would getting an ''M'' stone and putting it with ''H'' stones bring enough contrast for it to look intentional or would it just look weirdly off?

Thanks for the info on the refraction! It''s hard for me to picture it... in my head the yellow tints the other colors so you mostly see orange and yellow and green... hard to picture purple coming off of it but it must be really spectacular!

I have both a fancy yellow and a very light yellow (L, M) range diamond. For the fancy yellow, since the color is more intense, pairing it with G color side stones make pretty good contrast.

As for the L/M very light yellow diamond, the color is very subtle; sometimes it looks tinted while in some other lighting it looks white. I originally put a G color diamond pave halo around it and there is not too much contrast. The only effect is making the center stone looks off white. I then put a 24kt gold basket underneath the diamond to bring out the color. I tried the 18kt gold basket but it didn''t work too well since the yellowish color is too light. The 24kt gold basket improved the contrast but the basket kinda of makes the center center look champagnish at some lighting. Overall, I was not satisfied with the results. I ended up junking the halo setting/basket and wearing the very light yellow pear shape diamond solo as a pendant. The stone is very bright with a lot of brillance/fire and it is very pretty in its own right. However, it is neither white or yellow so picking side stones to for complement or contrast will not be easy.

 

[adamasgem]

Date: 9/7/2006 2:07:27 AM
Author: maxspinel

I need some clarification on brilliance vs. fire. I thought brilliance is primarily reflection of white light while fire is the separation of the white light into the different color spectrum, similar to the prism effects. Therefore, diamonds cut with smaller tables exhibit more fire while those with larger talbes exhibit more brilliance. A stone can''t achieve optimum fire and brilliance at the same time.

I am trying to understand your attached fire performance image. It is hard to distinguish what is fire vs. brilliance in the picture since the white and color reflection seems to co-mingle. For someone who doesn''t know too much about the technical aspects of the brilliance/fire measurement, I am guessing that the kittydock is some kind of GIA lighting setup which utlizes the LED (light emitting diode??) as sthe source.

Also, for comparison purposes, do you have a similar fire performance scope on a white diamond? This would help to illustrate if there is measurable differences in the fire display (intensity vs. weaker color in some sprectrum). Just like it was stated earlier, the yellowish body color is the result of the absorption of other colors, leaving the yellow as the remaining color to be reflected back to the viewer. However, since the refraction and other properties of diamond remains the same, the light entering the stone will be split into various spectrum color.

This is my E master stone under the same envirionment..

Any measurement of "brilliance" (or light return) is, by its very nature, going to have "fire" inherent in the measurement.

The KittyDock(TM) is the GIA new box to cut grade diamonds, incorporating 12 LEDs to try to show off fire. I use 10000light sources... Just a little more chance of aliasing results in GIA''s scheme..

 

[maxspinel]

Date: 9/7/2006 3:06:54 AM
Author: adamasgem

This is my E master stone under the same envirionment..

Any measurement of ''brilliance'' (or light return) is, by its very nature, going to have ''fire'' inherent in the measurement.

The KittyDock(TM) is the GIA new box to cut grade diamonds, incorporating 12 LEDs to try to show off fire. I use 10000light sources... Just a little more chance of aliasing results in GIA''s scheme..

I am trying to compare the image of the Y vs. E master stone side by side. The Y color master stone exhibits more and brighter yet narrower flashes/fire while the E color one has broader flashes. Based on the comparison, it seems cut instead of color is the main factor affecting the pattern and the amount of fire.

I am still confused about the difference between the brilliancescope and the fire scope. How different is the setup and if the brilliancescope is devised to measure brillance (white light return) and the fire acope is for the internal fire display (color light return).

Thanks

 

[adamasgem]

Date: 9/8/2006 2:39:20 AM
Author: maxspinel

Date: 9/7/2006 3:06:54 AM
Author: adamasgem

This is my E master stone under the same envirionment..

Any measurement of ''brilliance'' (or light return) is, by its very nature, going to have ''fire'' inherent in the measurement.

The KittyDock(TM) is the GIA new box to cut grade diamonds, incorporating 12 LEDs to try to show off fire. I use 10000light sources... Just a little more chance of aliasing results in GIA''s scheme..

I am trying to compare the image of the Y vs. E master stone side by side. The Y color master stone exhibits more and brighter yet narrower flashes/fire while the E color one has broader flashes. Based on the comparison, it seems cut instead of color is the main factor affecting the pattern and the amount of fire. Your observations are entirely correct, in my opinion. The smaller patterning (virtual facets) in not so well cut stones becomes evident in my Fire Performance Scope. The better the optical symmetry, the larger the areas of apparent facets of one color appear.

I am still confused about the difference between the brilliancescope and the fire scope. How different is the setup and if the brilliancescope is devised to measure brillance (white light return) and the fire acope is for the internal fire display (color light return).

I can''t speak directly to the brilliance scope methodologies, but it appears to offer a reasonably valid assessment vis-a-vie fire potential under a set of envirionments.

The photos in my Fire Performance Scope certainly tell a different type of story, and may be able to be used (at least the research I have done seems to indicate so), for a very good categorization of fire.
The photos, when compared with the old AGS cut grade, correlated extremely well from a visual perspective. The photos told you whether you had a well cut stone or not. Garbage was really evident.
When I get a chance I''ll dig up and post a photo of real bad cutting.

Thanks

 

[oldminer]

When we measure Brilliancy any fire present is included. Since Brilliancy is defined as the average gray scale value of the diamond in our lighting environment, then all the spectral colors become shades of gray and are included in Brilliancy. For this reason, we say Fire is a secondary measure. It is a variable component of total Brilliancy. Fire is more associated with lighting environment choice than a Brilliancy measure is.

I know, any lighting choice is arbitrary, and I fully expect no one to ever agree on a standard lighting environment for grading diamond light behavior. However, I am making the effort to use one of many possible standard environments across the board to measure all diamond light behavior. It seems a decent strategy although many people want to know about the environment, mostly for the sake of saying they have a superior one or just to be critical. If there was a lot of constructive criticism out there, things would be more pleasant sometimes. I just have adopted a hard nosed mentality when facing non-constructive criticism.

 

[adamasgem]

Date: 9/8/2006 2:13:42 PM
Author: oldminer
When we measure Brilliancy any fire present is included. Since Brilliancy is defined as the average gray scale value of the diamond in our lighting environment, then all the spectral colors become shades of gray and are included in Brilliancy. For this reason, we say Fire is a secondary measure. It is a variable component of total Brilliancy. Fire is more associated with lighting environment choice than a Brilliancy measure is.

In a manner of speaking, the ability to see fire depends on how much the total light is masking the pure spectral hues. I''ll disagree regarding a Brilliance measure, as it is HIGHLY dependent on the lighting envirionment..

I know, any lighting choice is arbitrary (not necessarily so), and I fully expect no one to ever agree on a standard lighting environment for grading diamond light behavior. KittyDock(TM)

However, I am making the effort to use one of many possible standard environments across the board to measure all diamond light behavior. It seems a decent strategy although many people want to know about the environment, mostly for the sake of saying they have a superior one or just to be critical. If there was a lot of constructive criticism out there, things would be more pleasant sometimes. I just have adopted a hard nosed mentality when facing non-constructive criticism.

Dave, constructively, there is a difference between an envirionment which RESULTS in the highest apparent discrimination between stones (e.g High angle lighting, which appears to have the highest efficiency of light return to a face up viewer) and an fixed unknown, undefined one, trying to be used for a qualitative (or quantitative) measure of the overall "goodness" of light return.

As long as the basis for the "magic" measure is unknown, no one in their right mind should accept that measure, except if you are a seller, and the "number" works for you.

A number without a paradigm for comparison is just a number..

Sorry, that is the way I feel it should be.

 

[adamasgem]

Here is what a particularly bad cut would look like... OLD AGS 7 cut class

 

[Garry H (Cut Nut)]

Interesting discussion.

Marty can you draw a direct correlation tto the fire in a given diamond in various lighting effects and the display of colors in your new scope?

I am worried that the gren could be counted as fire if you were going to use a pixel counter - as we know green is rarely ever seen.

I am writting this for the Cut Group for another purpose, which I will publish after the journal using it has been published - but it is relevant here too:

A good explanation of dispersion by Anton Vasiliev is paraphrased here (published 12 years ago in a work available in full at www.gemology.ru/cut/english/rainbow/5.htm )

Consider the observer, (which GIA did not in their published studies): A pupil diameter of 3 mm at a viewing distance of 25 cm creates an angular size of 0.7° for the possibility of light to enter the eye. For an observer to see a ‘pure’ spectral colour, a gem must have a high fan of angular dispersion. But because green is in the central region of the spectrum, there is a high chance that green will be mixed with other colours, and appear whiter. For this reason the greater the distance between the gem and the observer, the more pure the fire one can see. Alternatively less fire, but brighter flashes, can be seen in lower illumination conditions because our pupil opens wider.

Now consider the illumination type (which GIA did not in their published studies): To create a full spectrum a prism should be illuminated with a light that has a very small angular size, such as that from the sun, a fiber optic source through a pin hole, or a small lamp at a very great distance. When a light is larger and closer, as in most indoor situations, colors mix on the retina, degrading the purity of the observed color. Hence, good green fire requires illumination of the gem from a light source of small angular size. The source’s angular size affects the color purity in the same way that the observer's eye pupil size does.

The 15ct diamond on the left has been photographed in office lighting and shows predominantly blue coloured flashes, with some red and yellow, but green will rarely be seen for two reasons. Because the lights in the office are large in size and relatively close to a diamond, we can not see green flashes. The 9ct diamond on the right shows some green; it was photographed in partly shaded direct sunlight, effectively parallel rays of light (which is what i beleive you are modelling in your set up Marty). In addition both pupil and camera apertures’ are small because we are outdoors in very bright daylight. Our narrow pupil aperture allows us to see some green flashes without the merging of yellow & green or blue & green. An additional explanation can be found here www.gemology.ru/cut/english/grading1/4.htm. Both photographs were taken with the same Canon Ixus camera set to auto mode on author GH’s fingers.

 

[Cehrabehra]

what does that mean green is rarely ever seen, I see it all the time! I probably see yellow and blue more, but with these big facets I see all the colors all the time with ease. Why is green ''rarely seen''? What does that mean?

 

[Garry H (Cut Nut)]

Hey C, it is probably night time now where you are - so do this - go to different room / lighting types and count how many of each color flash you can see at each of a few glances.


Everyone else can try it too

 

[Cehrabehra]

Date: 9/8/2006 7:33:06 PM
Author: Garry H (Cut Nut)
Hey C, it is probably night time now where you are - so do this - go to different room / lighting types and count how many of each color flash you can see at each of a few glances.


Everyone else can try it too

well, just sitting here at my desk (it is not dark) and sticking the stone (dirty) into a beam from the window I would say the most predominant color is aqua (which really is "blue" if you consider the darker shade indigo) and then red and then blue and then green and then yellow. I didn''t see much purple though... I actually saw a fair amount of green, more than yellow. Blue and red were pretty tied but I saw more aqua than blue. It was all fairly even though for the most part. I suppose if you are being statistical about it green could be considered "rare" but I saw at least 10 flashes of it in about 30 seconds. I''m admitedly too lazy to try it in another room LOL ;D

 

[Garry H (Cut Nut)]

Date: 9/8/2006 7:39:35 PM
Author: Cehrabehra

Date: 9/8/2006 7:33:06 PM
Author: Garry H (Cut Nut)
Hey C, it is probably night time now where you are - so do this - go to different room / lighting types and count how many of each color flash you can see at each of a few glances.


Everyone else can try it too

well, just sitting here at my desk (it is not dark) and sticking the stone (dirty) into a beam from the window I would say the most predominant color is aqua (which really is ''blue'' if you consider the darker shade indigo) and then red and then blue and then green and then yellow. I didn''t see much purple though... I actually saw a fair amount of green, more than yellow. Blue and red were pretty tied but I saw more aqua than blue. It was all fairly even though for the most part. I suppose if you are being statistical about it green could be considered ''rare'' but I saw at least 10 flashes of it in about 30 seconds. I''m admitedly too lazy to try it in another room LOL ;D

OK, but you are using parallel rays from a light source that is effectively very very small - the sun.
Try the artificial light - you should expect a different result.

Also try to not look for 3 seconds at hunderds of flashes - it would be good to say do 3 fixed positions with maybe 5 flashes each time. Then you can quanitify the %''s of each color for each room / lighting type.

 

[Cehrabehra]

Date: 9/8/2006 7:46:09 PM
Author: Garry H (Cut Nut)

OK, but you are using parallel rays from a light source that is effectively very very small - the sun.
Try the artificial light - you should expect a different result.

Also try to not look for 3 seconds at hunderds of flashes - it would be good to say do 3 fixed positions with maybe 5 flashes each time. Then you can quanitify the %''s of each color for each room / lighting type.

one of the problems I incurred during this experiment was how the heck do you tally them? I mean you''ve got like 5 going off at once and changing colors mid flicker sometimes, you see so many, how are you to keep track? I couldn''t keep numbers I just went off of what I saw and that was biased every time by, "Okay I''m looking for blues, I see blues... okay I''m looking for yellows okay I see some yellows... Okay I''m looking for reds, yep there are the reds..." and just sitting there waiting for them to pop in general was like okay I''m seeing them all LOL

statistically green might be the least common color, but I have no trouble finding green flashes and even catching them on film.

Here is a full sized picture (not shrunk or enlarged) of pinfire in my stone... if anyone is interested they could count the incidence of color LOL

 

[adamasgem]

Date: 9/8/2006 7:07:07 PM
Author: Garry H (Cut Nut)


Interesting discussion.

Marty can you draw a direct correlation tto the fire in a given diamond in various lighting effects and the display of colors in your new scope? Can't honestly answer that question, that is what simulations are for. I have about 10,000 point sources of white light illuminating the chamber, so the photos illustrate the ability to produce fire.

I am worried that the gren could be counted as fire if you were going to use a pixel counter - as we know green is rarely ever seen. Well, green is part of the spectral dispersion produced, why shouldn't it be counted. True, that color mixing comes into play, and that my scope probably has better "resolution" than the eye, with regard to being able to "see" what is happening.

I am writting this for the Cut Group for another purpose, which I will publish after the journal using it has been published - but it is relevant here too:

A good explanation of dispersion by Anton Vasiliev is paraphrased here (published 12 years ago in a work available in full at www.gemology.ru/cut/english/rainbow/5.htm )

Consider the observer, (which GIA did not in their published studies): A pupil diameter of 3 mm at a viewing distance of 25 cm creates an angular size of 0.7° for the possibility of light to enter the eye. For an observer to see a ‘pure’ spectral colour, a gem must have a high fan of angular dispersion. But because green is in the central region of the spectrum, there is a high chance that green will be mixed with other colours, and appear whiter. I would say amybe appear as a different color, not necessarily whiter, becuase whiter implies that you are picking up the entire spectrum at once. For this reason the greater the distance between the gem and the observer, the more pure the fire one can see. In optically symmetric stones. Stones with "pinfire" get mushed together and what you see is white, the Opal analogy. Alternatively less fire, but brighter flashes, can be seen in lower illumination conditions because our pupil opens wider. I think that may be an incorrect statement. You can't necesarily "resolve" fire because it is being comingled with glare.

Now consider the illumination type (which GIA did not in their published studies): To create a full spectrum a prism should be illuminated with a light that has a very small angular size, such as that from the sun, a fiber optic source through a pin hole, or a small lamp at a very great distance. When a light is larger and closer, as in most indoor situations, colors mix on the retina, degrading the purity of the observed color. Hence, good green fire requires illumination of the gem from a light source of small angular size. The source’s angular size affects the color purity in the same way that the observer's eye pupil size does. The angular size of my prototype sources differ depending on the elevation from the stone, back of the envelope range from about 0.75 to 1.4 degrees solid angle. System can be built to give a tighter range of angular source sizes. I have other "source baffles" and could make each "source" uniform of any size I wan't to.

The 15ct diamond on the left has been photographed in office lighting and shows predominantly blue coloured flashes, with some red and yellow, but green will rarely be seen for two reasons. Because the lights in the office are large in size and relatively close to a diamond, we can not see green flashes. I don't think that is necessarily the reason. The 9ct diamond on the right shows some green; it was photographed in partly shaded direct sunlight, effectively parallel rays of light (which is what i beleive you are modelling in your set up Marty). Paritially true. In addition both pupil and camera apertures’ are small because we are outdoors in very bright daylight. Our narrow pupil aperture allows us to see some green flashes without the merging of yellow & green or blue & green. An additional explanation can be found here www.gemology.ru/cut/english/grading1/4.htm. Both photographs were taken with the same Canon Ixus camera set to auto mode on author GH’s fingers.

 

[Cehrabehra]

here''s another pic... seems like green is more common!

 

[Cehrabehra]

One more, sorry its so huge, wanted to be accurate... none of this is broad fire just pinfire, but as such I think it''s fairly good cross section, no? Does digital photography tend to pick up more green than the eye does? if yes, can that be proven?

because it is in the middle of the spectrum, like any good bell curve, you''d likely find MORE of it, not less of it... but I could see how it is easily drowned out by blue and yellow just as orange can be. But in the spectrum orange has a fairly short span I think where as green is one of the longer whatevers, isn''t it? whatever is the unscientific term for what I''m forgetting... the bandwidth so to speak of the spectral color lol

 

[Cehrabehra]

Okay this is from that last pic, just a little piece of it toward the middle left... and it describes what I think garry was saying about white drowning out green?