Diamond fire vs spectra colour

[Texas Leaguer]

@Texas Leaguer
P.S. I don’t expect you to comment, I just found it to be an “interesting” post

Probably a case of someone running their social media taking liberties with the actual messaging around the GIA cut research. It seems everyone is susceptible to engaging in hyperbole!

 

[Malha777]

Great article John. But note that the green is almost totally absent in all your real life photos. You might need to explain that.

Is there a reason why?

Thanks everyone! Lots of very interesting posts

 

[yssie]

Is there a reason why?

Thanks everyone! Lots of very interesting posts

http://www.gemology.ru/cut/english/rainbow/3.htm
http://www.gemology.ru/cut/english/grading1/6.htm
https://www.pricescope.com/articles/fractioning_color_gem
https://www.pricescope.com/communit...to-capture-green-flashes-on-a-diamond.246342/

 

[Garry H (Cut Nut)]

Is there a reason why?

Thanks everyone! Lots of very interesting posts

Thanks Yssie. There is an image somewhere on the old MSU OctoNus site that explains the abscence of green.
If you could see green it is usual that you will see some blue and some yellow and orange which equals white.
Experiment.
Get a big sparkly diamond. A spot light not flood light. Find a flash and move the stone very slowly so that you explore the flash.
It starts blue, goes white and then red as you move the stone the tinest bit.
or vice a versa.

Most of the green you see in photos is flare which is usually a camera artefact.

 

[Garry H (Cut Nut)]

Read around about page 91 and 92.

http://www.gem.org.au/ckfinder/userfiles/files/GAA_Journal_V25_No3_web2(1).pdf

 

[Malha777]

In terms of conversation and definitions, I'd add this:

• Dispersion occurs physically, within the diamond.
• Absorption (when relevant) occurs physically, within the diamond.
• "Seeing" Fire occurs physiologically, at the human eye.

So what you "see" isn't just about the illumination scenario and cut-geometry (or absorption spectroscopy - which is another can of gummis). It's also about your pupil constriction or dilation, your specific physiology - people see color differently - whether you're wearing glasses, etc.

I wrote an article for IGI on the topic a couple of months ago, with graphics and photos, in case it's interesting.

Linked here: Dispersion & Fire are not the same thing.

I very much enjoyed reading the article and I was wondering if this part

“If a dispersive-fan passes over your eye and is wider than your pupil’s diameter you will see a colored flash. If a dispersive fan passes over your eye but is smaller than your pupil’s diameter the light recombines and you see a white flash. If the fan is too small or weak you see nothing. In optimal cases a single, wide dispersive-fan passing across your pupil may cause you to see a full suite of shifting chromatic colors.”

Is the reason why RBC having ideal cut with a lower half percentage of 75 have usually more fire than other with 85% that will show more white flashes instead?

 

[John P]

Great article John. But note that the green is almost totally absent in all your real life photos. You might need to explain that.

Thank you for the opportunity @Garry H (Cut Nut). And you are spot-on.

In essence, green is situated between the IR (infra-red) and visible red and UV (ultra-violet) and visible violet. So it becomes the stepchild of the extremes. Rarely seen compared to visible flashes of red,yellow, blue and purple.

Here's a better look at the real-life situation via video. Thanks to the magic of "steady hands" you can see the green there, in the middle of the dispersive-fan. But, physiologically, it's indeed the most difficult to capture with your pupil.

 

[John P]

I very much enjoyed reading the article and I was wondering if this part

“If a dispersive-fan passes over your eye and is wider than your pupil’s diameter you will see a colored flash. If a dispersive fan passes over your eye but is smaller than your pupil’s diameter the light recombines and you see a white flash. If the fan is too small or weak you see nothing. In optimal cases a single, wide dispersive-fan passing across your pupil may cause you to see a full suite of shifting chromatic colors.”

Is the reason why RBC having ideal cut with a lower half percentage of 75 have usually more fire than other with 85% that will show more white flashes instead?

I'm glad you enjoyed the overview @Malha777.

Yes to your question. The pavilion mains are the primary drivers of light return. When the lower halves are shorter the pavilion mains are wider. Greater surface area means a larger starting-point for the dispersive-fans. This is why antique cuts, with their insanely wide pavilion mains and high crowns promoted such big flashes of perceived fire.

There is another component: Compound mirror integrity. Essentially, increasing the size of the reflective surfaces within the diamond.

It's past my bedtime, but here is a thread touching on that which may be interesting.

CBI fire

So, I bought a CBI diamond with the following dimensions: Table 57% Crown Angle 34.5 degrees Crown Percentage 14.8% Pavilion Angle 40.8 degrees Pavilion Percentage 43.1% Depth 61.5% Star 51 Lower Girdle Facet 77 It’s beautiful, of course, but I still wonder about FIRE. When I was initially...

www.pricescope.com

Fun thread!

 

[AV_]

@John Pollard Several of your latest posts argue for historical features of the round brilliant - as if there were a few half-cut on your mind

 

[matt_k]

G colored EC.
Indirect sunlight, at sunset.



OEC (Nancy) G-I color range.
Indirect sunlight, mid-day at the beach.


Vintage Cut Asschers by Yoram at GemConcepts. F-H color range.
Indirect Sunlight at sunset.

re: video clip, in the background: let the pigeon drive the bus!!!

 

[Serg]

John,
re:Shallow or Deep geometries cause light to exit through the pavilion, suppressing brightness and dispersion.

I would like to know a sample of "Shallow" proportions that creates leakage considerably higher than "Proportionate" diamonds.

 

[Serg]

Thank you for the opportunity @Garry H (Cut Nut). And you are spot-on.

In essence, green is situated between the IR (infra-red) and visible red and UV (ultra-violet) and visible violet. So it becomes the stepchild of the extremes. Rarely seen compared to visible flashes of red,yellow, blue and purple.

Here's a better look at the real-life situation via video. Thanks to the magic of "steady hands" you can see the green there, in the middle of the dispersive-fan. But, physiologically, it's indeed the most difficult to capture with your pupil.

To see a green flash you need use a light source with less divergence angle than dispersion angle. Most typical lights source( except the sun) have much bigger divergence angle than typical diamond dispersion angle that will mix green color with red and blue color's.


see detail explanation here http://www.gemology.ru/cut/english/grading1/4.htm

 

[AV_]

I would like to know a sample of "Shallow"

WWW - shallows with point or line culets, various crown constructions & outright flat windows too

 

[Matthews1127]

re: video clip, in the background: let the pigeon drive the bus!!!

Showing my mom side....lol!!

 

[John P]

John,
re:Shallow or Deep geometries cause light to exit through the pavilion, suppressing brightness and dispersion.

I would like to know a sample of "Shallow" proportions that creates leakage considerably higher than "Proportionate" diamonds.

Hi Sergey. First, thank you for reading the article.

Second, you raise a good point of order. We know brightness suppression in shallow sets is due to obstruction through tilt, and potential girdle-reflection. We know traditional light-path diagrams seen in teachings and stores are folly. Garry has crusaded about that for years.

The challenge is the KISS principal: In live classes I can explain how those traditional models are wrong. I've done it many times. On average, 20% of the jewelers in the room are with me and super-excited to get the information. But 60% struggle with the idea that the diagrams posted in every store in the USA are wrong, and the other 20% just want the techno-babble to be over.



It's a matter of choosing a battle: For the article in question the goal is illustrating that dispersion occurs physically, within the diamond, whereas perception of fire occurs physiologically, at the human eye.

Meanwhile I've changed the comment you highlighted to this: "Shallow or Deep geometries cause light behavior deficits which can suppress brightness and dispersion." I appreciate the opportunity to improve the piece.

The world's millions (tens of millions?) of incorrect diagrams on every store counter should be changed. So should the one I used, ultimately.

That's another battle entirely. But this exchange convinces me to carry it forward. So thank you for that. And thanks again for spending time reading it. Traditional folly aside, I hope you enjoyed the topic.

 

[Serg]

Hi Sergey. First, thank you for reading the article.

Second, you raise a good point of order. We know brightness suppression in shallow sets is due to obstruction through tilt, and potential girdle-reflection. We know traditional light-path diagrams seen in teachings and stores are folly. Garry has crusaded about that for years.

The challenge is the KISS principal: In live classes I can explain how those traditional models are wrong. I've done it many times. On average, 20% of the jewelers in the room are with me and super-excited to get the information. But 60% struggle with the idea that the diagrams posted in every store in the USA are wrong, and the other 20% just want the techno-babble to be over.



It's a matter of choosing a battle: For the article in question the goal is illustrating that dispersion occurs physically, within the diamond, whereas perception of fire occurs physiologically, at the human eye.

John,
I believe, working KISS solutions can not be established on Wrong statements.
When you use wrong statements you just simplify your job but you do not achieve real KISS solution.

 

[cflutist]

@John Pollard

This is all too technical for my aging brain.
So what are we seeing here?
Dispersion and/or fire?
3 CBIs
E-VS1 center
F-VS1 and VS2 side stones

 

[John P]

John, I believe, working KISS solutions can not be established on Wrong statements. When you use wrong statements you just simplify your job but you do not achieve real KISS solution.

Sergey,

Truth. I already agreed and made the edit. Thanks for the perspective.

Larger questions -

• Have you image-Googled "diamond cut diagram shallow deep" ?
• If so, what are you doing to address this at a more meaningful level?

Pricescope is easily convinced. Is there a way to convince the rest of the world? And how can we help?

 

[Serg]

Sergey,

Truth. I already agreed and made the edit. Thanks for the perspective.

Larger questions -

• Have you image-Googled "diamond cut diagram shallow deep" ?

In first 15th images I see 3 with correct ray tracing. So now 20% such diagrams are not completely wrong that is much better result than several years ago. Unfortunately even these 20% have unreal proportions for shallow and steep diamonds because the real goal was is to create scare instead to give education , knowledge .

Until now most companies push consumers to buy "Ideal cut" then by using unreal "diamond cut diagrams steep-shallow". Scare marketing is very destructive approach for diamond business

 

[Serg]

Sergey,

• If so, what are you doing to address this at a more meaningful level?

We publish articles, educational information with correct information


and also we are developing work shop about diamond beauty.
here You can see small part that we are doing to save diamond business .
I hope we are not scare consumers

 

[matt_k]

Showing my mom side....lol!!

Love it! I read all of those Mo Willems books to my son a few years ago( knuffle Bunny, all the pigeon books, all the piggie and elephant books).

 

[matt_k]

Thank you for the opportunity @Garry H (Cut Nut). And you are spot-on.

In essence, green is situated between the IR (infra-red) and visible red and UV (ultra-violet) and visible violet. So it becomes the stepchild of the extremes. Rarely seen compared to visible flashes of red,yellow, blue and purple.

Here's a better look at the real-life situation via video. Thanks to the magic of "steady hands" you can see the green there, in the middle of the dispersive-fan. But, physiologically, it's indeed the most difficult to capture with your pupil.

My CBI put out the same little colored spots(including the tiny green bits) in the exact same way not long ago--- but over a smaller space, and while sitting in my car on a VERY sunny day.

 

[Garry H (Cut Nut)]

Here is a video explaining my frustration

 

[AV_]

This should be possible to tell at a glance - the charts do not have this quality, the correct & the incorrect are a tough muddle to read & look identical until one has understood them.

 

[Malha777]

Here is a video explaining my frustration

That’s absolutely amazing!! Thanks so much for sharing

 

[Garry H (Cut Nut)]

In first 15th images I see 3 with correct ray tracing. So now 20% such diagrams are not completely wrong that is much better result than several years ago. Unfortunately even these 20% have unreal proportions for shallow and steep diamonds because the real goal was is to create scare instead to give education , knowledge .

Until now most companies push consumers to buy "Ideal cut" then by using unreal "diamond cut diagrams steep-shallow". Scare marketing is very destructive approach for diamond business

Sergey the first one that is correct has 2 diamonds that do not exist. The others are stolen from me and used online. What is used instores are never that complex.

There is an error in your graphic with the deep 43.6 degree pavilion

 

[Serg]

Sergey the first one that is correct has 2 diamonds that do not exist. The others are stolen from me and used online. What is used instores are never that complex.

There is an error in your graphic with the deep 43.6 degree pavilion

Garry,
It is not an error, it is KISS.
Please check ray path for pavilion halves that create neailhead for diamond with Pavilion angle 43.6

 

[John P]

Garry, It is not an error, it is KISS.

LOL

In first 15th images I see 3 with correct ray tracing. So now 20% such diagrams are not completely wrong that is much better result than several years ago. Unfortunately, even these 20% have unreal proportions for shallow and steep diamonds because the real goal was is to create scare instead to give education , knowledge

20% sounds right. You're seeing a reflection of what I told you above. 20% are willing to adapt - even if they don't "get it" quite correctly. 60% resist changing their erroneous KISS diagrams and 20% don't want to discuss the topic.

Until now most companies push consumers to buy "Ideal cut" then by using unreal "diamond cut diagrams steep-shallow". Scare marketing is very destructive approach for diamond business

It's why I prefer using the word 'proportionate' in my training materials.

 

[John P]

We publish articles, educational information with correct information

I was there for your oral and poster in 2006, with enthusiasm (was it really 14 years ago?). All of those materials are a great resource for those of us who know how to find them. But how are you reaching others?

I've trained jewelry pros around the USA for a dozen years. During corona I've done a series of diamond and gemstone webinars with average attendance of 100+ pros per session. Candidly, topics like those we're discussing remain completely unknown until I introduce them. To career jewelers.

How can that change? As Garry Einstein demonstrates above, those incorrect diagrams are folly. Surely the industry can agree to that. Have you approached a gemological entity with global reach and extended the opportunity to issue a worldwide correction - potentially replacing those diagrams with accurate ones under their masthead? Do you want help doing that?

and also we are developing work shop about diamond beauty here. You can see small part that we are doing to save diamond business. I hope we are not scare consumers

That's a useful page. Following the 20-60-20 rule I believe many pros would be interested, if they were exposed to it. RE average consumers (away from PS), it's a lot to swallow, but I can see ways to frame the material in smaller bites. We have a saying in education: Small bites keep the students hungry.

 

[Diamond Girl 21]

In terms of conversation and definitions, I'd add this:

• Dispersion occurs physically, within the diamond.
• Absorption (when relevant) occurs physically, within the diamond.
• "Seeing" Fire occurs physiologically, at the human eye.

So what you "see" isn't just about the illumination scenario and cut-geometry (or absorption spectroscopy - which is another can of gummis). It's also about your pupil constriction or dilation, your specific physiology - people see color differently - whether you're wearing glasses, etc.

I wrote an article for IGI on the topic a couple of months ago, with graphics and photos, in case it's interesting.

Linked here: Dispersion & Fire are not the same thing.

Great article. Thanks for sharing.