Light Performance vs Color

[kenny]

A D is more clear and will absorb less light than a G, which will absorb less light than a J, etc.

So yes, if cut identically and of identical clarity a D will be brighter than a J or even an E.
That is a physical fact that is beyond dispute!
But whether the human eye could detect it is another matter.

Next, even if the human eye could detect the difference, whether the difference is worth X dollars is another matter, still.
You pay tons more money for a very slight change of appearance when it comes to color grades.

But if you absolutely MUST have the brightest diamond [even if it is just 0.1% brighter for 3 times the price - these numbers are made up] get a D.

But IMHO when it comes to getting a bright diamond cut is more important than color.
Put a well-cut J next to a poorly cut D and I'll bet almost everyone will say the J looks brighter.
This is because the D could let tons of light leak out the bottom, while the well-cut J will be returning almost all of the light back out the top.

Cut is king.

 

[Regular Guy]

Date: 10/13/2009 1:21:25 PM
Author: AshNZ

Good to know I can save my money on color.

Ash

Sounds like you get the principle of lowest hanging fruit...which is the main point.

You might value John Pollard's last post here.

Hard to know exactly what to point you to...as to what might make the most difference.

That's why I was motivated to direct you to a local expert, vs. one thing or another. You can read here lots about appropriate uses of technology, many of which trump HCA, but none of which, taken by themselves, may get you to the "perfect cut."

 

[AshNZ]

Date: 10/13/2009 4:02:47 PM
Author: Regular Guy

Date: 10/13/2009 1:21:25 PM
Author: AshNZ

Good to know I can save my money on color.

Ash

Sounds like you get the principle of lowest hanging fruit...which is the main point.

You might value John Pollard''s last post here.

Hard to know exactly what to point you for...as to what might make the most difference.

That''s why I was motivated to direct you to a local expert, vs. one thing or another. You can read here lots about appropriate uses of technology, many of which trump HCA, but none of which, taken by themselves, may get you to the ''perfect cut.''

Hmmm, perhaps I never explained myself clearly enough - the entire point of this thread is to ''Science for Science sake''. I want to explore the theoretical limits. When I understand our current limitations I can accurately position myself as a consumer to purchase. When that time comes, I will incorporate all of the ''Human'' elements to buying a diamond, ie:

Human optics (G vs D)
Human emotion (Tiffanys etc)

And make the best purchase possible within my budget.

Don''t worry about that now! Let''s continue to delve into the theory - we''ll all learn a little

Ash

 

[Rockdiamond]

Date: 10/13/2009 2:36:47 PM
Author: kenny
RD, yes perhaps when cutting to optimize color strength you may occasionally happen to end up with good light performance too.

But I think the following principle is sound:
With fancy colored rough there is MUCH more financial reward in cutting to achieve a higher color grade than in cutting to achieve better light performance.

The term "light performance" never comes out of the mouth of a large percentage of the world''s best diamond cutters.
In fact, the best cutters of Fancy Colored Diamonds are VERY interested in how bright the stones appear, in addition to maximizing perceived color.
It''s not an either or situation. You need both to be successful in this highly competitive marketplace.

Again we''re discussing subjective qualities, and putting objective values to them.

 

[Regular Guy]

Date: 10/13/2009 4:10:14 PM
Author: AshNZ

Hmmm, perhaps I never explained myself clearly enough - the entire point of this thread is to 'Science for Science sake'. I want to explore the theoretical limits.

I don't think I ever really presumed anything else, per se.

The question could be...what variables make a difference for light performance.

Follow the ball as to what makes a difference, and how it can be measured, hierarchically, and relative value can be assessed that way.

For example, you could try to measure how much light and heat is increased in a house, when you bring a candle into the house. But...if the house is on fire, this become more incidental in the scheme of things.

Regards,

P.S. Likewise, you'll see a fair amount of excitement on the board about H&A and optical patterning, but experts will know that the crown & pavilion relationships will overall trump that...despite the fact that the patterning, independent of those relationships, will make its own difference.

 

[Rockdiamond]

I really love the basis of your example Ira.
Say we lit a match in the basement of a three story home.
Without question there would be a measurable increase in the temperature of the house ( with some sort of "super thermometer").
There''s absolutely no way a human could "feel" the difference on the third floor, but it surely exists.

My position is that , unlike the incremental increase in temperature in the example above which is objective, the entire concept of "light performance" and how it affects the visual aspects of a diamond is NOT accepted science.

Commercial science, maybe. There is every bit as much Human emotion in judging reflector images as there is in Tiffany''s showcases.

Are reflector images broadly accepted physics? No.
Which calls into question the "science for science sake" aspect..... if we can''t "quantify" the results of reflector tests with meaningful data, we can''t explore the "theoretical limits"

 

[kenny]

Here is a fascinating read about cutting fancy-colored diamonds for top light performance.

A few surprises here.

It says that only 10% could be recut for optimum light performance without going down a color grade.

 

[Rockdiamond]

Not a whole lot surprising there Kenny.
It''s a "puff peice" for 8star.
A nine year old ad- for a product that still does not exist on the market.
I strongly disagree with some of the advertising "facts"- as it seems they are putting words in Langerman''s mouth.

I just saw an incredible carat and a quarter Fancy Blue Emerald Cut- VS1, that was cut both for beauty, color, AND yeild. there was no "fat" on this $300,000 diamond. The cut was amazing.
I can''t recall seeing a colorless emerald cut that I would say is "better" cut.

It''s the successful act of balancing these three aspects that separates the world''s best cutters of Fancy colors from a larger group that does cut only for yeild and color.
I agree, there''s a lot of crappy makes you''ll see in fancy colors. But by no means all.

 

[Allison D.]

To the extent there were some ridiculously minute measureable differences due to absorption, any differences would be imperceptible in a practical sense. Measureable, maybe....but perceptible? I don''t believe so.

 

[Todd Gray]

Date: 10/13/2009 4:11:10 PM
Author: Rockdiamond
The term ''light performance'' never comes out of the mouth of a large percentage of the world''s best diamond cutters.

This is an interesting statement...

What is the defining factor which determines which diamond cutters are the world''s best?

Are they the diamond cutters with the highest annual volume? The diamond cutters who produce the ''best cut diamonds'' in terms of visual performance? The diamond cutters who produce the best colorless diamonds? The diamond cutters who produce the best fancy color diamonds?

The basis of the statement needs to be clarified in order to be valid and I mention this because I know that the cutters who many of us work with frequently think and talk about ways to improve visual performance in order to maximize the value of their production and continue to raise the bar pertaining to beauty and visual performance - so perhaps I''m not working with the world''s best diamond cutters

and need to hang out with a new crowd

I''m going to go out on a limb here and guess that you''re referring to the world''s best diamond cutters who produce fancy colors because the discussions I''ve had with those guys usually revolve around cutting the rough to maximize intensity of color and they look at me like I''m an alien devoid of mental capacity when I talk about visual performance.

 

[kenny]

RD has been fighting against good cut since he joined.

His interests are obvious.

 

[Rockdiamond]

Date: 10/13/2009 7:05:37 PM
Author: Todd Gray

Date: 10/13/2009 4:11:10 PM
Author: Rockdiamond
The term 'light performance' never comes out of the mouth of a large percentage of the world's best diamond cutters.

This is an interesting statement...

What is the defining factor which determines which diamond cutters are the world's best?

Are they the diamond cutters with the highest annual volume? The diamond cutters who produce the 'best cut diamonds' in terms of visual performance? The diamond cutters who produce the best colorless diamonds? The diamond cutters who produce the best fancy color diamonds?

The basis of the statement needs to be clarified in order to be valid and I mention this because I know that the cutters who many of us work with frequently think and talk about ways to improve visual performance in order to maximize the value of their production and continue to raise the bar pertaining to beauty and visual performance - so perhaps I'm not working with the world's best diamond cutters

and need to hang out with a new crowd

I'm going to go out on a limb here and guess that you're referring to the world's best diamond cutters who produce fancy colors because the discussions I've had with those guys usually revolve around cutting the rough to maximize intensity of color and they look at me like I'm an alien devoid of mental capacity when I talk about visual performance.

Good point Todd. my statement could be ambiguous, if the context is not made clear.
Some of the world's finest cutters DO discuss "Light Performance" as is discussed here on PS- and they post here as well.

As a percentage of how many fine cutters exist in the world, the fine cutters represented here are a tiny number.

Today, it only makes sense that if we're talking about "fine make" and round diamonds, cutters have to be able to achieve AGS0 or GIA EX to compete.
That could easily be taken to mean "light performance" as it's talked about here on PS- but not in all cases either. As regular readers know there are some GIA EX cut grades ("Steep Deep") that are frowned upon here on PS.
There are many excellent cutters that do not post here, who do not use the term "light performance" nor cut using ASET.

It's also true that many exotic natural fancy colors have "funky" makes- and even true that such funkiness does not necessarily reduce their value or desirability.
I agree that many cutters of fancy colors don't produce diamonds we'd call "well cut"

It's taken a lot of work, but over the years I've found cutters of Fancy Colors that strive for incredibly fine makes- even by colorless diamond standards.
Like anything else, it's specialty. There are cutters specializing in fancy Colors and Fine make.
Lucky for me, because I value a great make ( well cut diamond) as much as anyone.

I might have different ideas of exactly what constitutes a great make than the prevailing attitude here on PS- but I can honestly say that in the diamond industry- looked at in the broader sense- there are different ideas about what constitutes the "best" make.

 

[Dancing Fire]

Date: 10/13/2009 8:28:54 PM
Author: Rockdiamond

I might have different ideas of exactly what constitutes a great make than the prevailing attitude here on PS- but I can honestly say that in the diamond industry- looked at in the broader sense- there are different ideas about what constitutes the ''best'' make.

yup,this has been going on for many yrs. RD''s pair of eyes VS the world.

 

[adamasgem]

Date: 10/13/2009 1:13:25 PM
Author: oldminer
Dr. Aggarwal, the principal of ImaGem, Inc., www.imageminc.com has advised me as follows: The light return from a D color identical in all respects to a G color would vary so little due to the color difference that it would be less than any machine error of the tool used to measure such a difference. So, in spite of what makes sense about absorption, there is no measure of less light return based on such minor color differences.

Dave.. Please correct me if I am wrong, but didn''t you quote your elite Dr Aggarwal in effect saying that you couldn''t differentiate the color grade between a D and a G with a machine, or at least, his machine?????

 

[Karl_K]

like anything else with diamonds there are no easy answers.
For example longer light paths == less performance is not correct.
Octavia has the longish light paths and is super-bright.
The highest performance a princess cut can achieve will be in a stone with longer light paths compared to other high performance princess cuts but shorter than most low performance ones.
The higher performance can easily make up for any absorption loses.

As to where the PS advise comes from it comes from this same topic reaching the same conclusions years ago.
There is not a real world difference in the higher color grades H and up and very very little J and up.
Not enough to matter much anyway.

 

[AshNZ]

Date: 10/14/2009 11:30:31 AM
Author: Karl_K
like anything else with diamonds there are no easy answers.
For example longer light paths == less performance is not correct.
Octavia has the longish light paths and is super-bright.
The highest performance a princess cut can achieve will be in a stone with longer light paths compared to other high performance princess cuts but shorter than most low performance ones.
The higher performance can easily make up for any absorption loses.

As to where the PS advise comes from it comes from this same topic reaching the same conclusions years ago.
There is not a real world difference in the higher color grades H and up and very very little J and up.
Not enough to matter much anyway.

Just to be clear - what you suggest isnt true.

Ray path length is always detrimental to light performance. The longer the ray path within the diamond, the more absorbtion occurs, the less light performance.
Therefore, color, and ray path length affect light performance. But, What you say about real world light performance does appear to be true - any performance lost from absorbtion is incredibly small (according to an earlier answer in this thread) and not a real factor.

The high performance cut you refer to will be a high performer because of reflection angles. Any potential performance lost to absorbtion is infintessimally small when compared to light performance from reflections.

Ash

 

[Karl_K]

Date: 10/14/2009 11:50:47 AM
Author: AshNZ


Just to be clear - what you suggest isnt true.


Ray path length is always detrimental to light performance. The longer the ray path within the diamond, the more absorbtion occurs, the less light performance.

I was 100% correct, the angles and how the light behaves in the diamond are far more important than absorption loses.
For example a diamond with longer light paths that returns 10% more light and gives up .05% to absorption is still 9.95% brighter.

 

[glitterata]

Ash, what is your definition of "light performance"?

Unless you have a solid definition that corresponds to some meaningful and desirable visual property of diamonds, optimizing it won''t do you a lick of good.

 

[Karl_K]

Date: 10/14/2009 11:50:47 AM
Author: AshNZ

The high performance cut you refer to will be a high performer because of reflection angles. Any potential performance lost to absorbtion is infintessimally small when compared to light performance gain from more efficient reflections to the eye.


Ash

Does that help?

 

[kenny]

There are two separate things:

1. Whether a human can detect it or not, diamond body color attenuates light . . .
a. More body color means more attenuation
b. A longer a light path means more attenuation (unless it is a D)

2. Well cut diamonds return more light back out the crown, poorly cut diamonds let some leak out the back

And good cut is MUCH more important than body color when it comes to getting a bright-looking diamond.

 

[glitterata]

Also, Ash, why do you assume that if you see a difference between what you think and what someone else has said, they''re wrong? Why not consider the possibility that YOU''RE the one who''s wrong?

Instead of announcing that people (like Karl) who know far more about the subject than you do are wrong, try pointing out the discrepancy and asking for help understanding it. Then you will be better liked around here and less annoying.

 

[Karl_K]

Date: 10/14/2009 12:02:02 PM
Author: kenny
There are two separate things:


1. Whether a human can detect it or not, diamond body color attenuates light . . .

a. More body color means more attenuation

b. A longer a light path means more attenuation


2. Well cut diamonds return more light back out the crown, poorly cut diamonds let some leak out the back

1b: a diamond with a longer light path can have superior light return due to how it handles light.

 

[AshNZ]

Kark_K, to quote

"For example longer light paths == less performance is not correct."

Sorry Karl, on it''s own (which is how you made the statement), this is incorrect. Longer ray length DOES equal less performance.
I don''t know how to make it clearer than that. Unless you want to prove to me that there is no such things absorbtion...
Perhaps jump on Wikipedia...

Now, I agree with you when you combine it with other elements, but in every case longer ray paths is bad (due to absorbtion), it is just completely outweighted by other factors.

Date: 10/14/2009 11:56:44 AM
Author: glitterata
Ash, what is your definition of ''light performance''?

Unless you have a solid definition that corresponds to some meaningful and desirable visual property of diamonds, optimizing it won''t do you a lick of good.

Good question. Firstly, is there an ''Industry Standard''?
My definition (simplistically) was the ''inverse of leakage'' Truth be told, I don''t have the knowledge to have a strong grasp on this just yet.

Ash

 

[AshNZ]

Date: 10/14/2009 12:05:26 PM
Author: glitterata
Also, Ash, why do you assume that if you see a difference between what you think and what someone else has said, they''re wrong? Why not consider the possibility that YOU''RE the one who''s wrong?

Instead of announcing that people (like Karl) who know far more about the subject than you do are wrong, try pointing out the discrepancy and asking for help understanding it. Then you will be better liked around here and less annoying.

I am a physicist glitterata. What Karl is stating is incorrect. This is not opinion based, it is literature based. Feel free to research it yourself. I am sure Karl is hugely knowledgable about a great deal of things I know little or nothing about, but when it comes to physics, I have signicant training and work in the industry. I don''t see what the fuss is about - we are here to learn, if people get their feathers ruffled by simply being challenged or corrected we''d never get anywhere.

Are you annoyed at learning something new?

Ash

 

[Karl_K]

Date: 10/14/2009 12:08:09 PM
Author: AshNZ
Kark_K, to quote


'For example longer light paths == less performance is not correct.'


Sorry Karl, on it's own (which is how you made the statement), this is incorrect. Longer ray length DOES equal less performance.

What your are missing is:
absorption is tiny compared to gains from more efficient reflectors.

For example the light path is about 2x a super-ideal RB(which are around .98 on this light return scale) but the light return is ~10% higher face up, even if you lose .5% from absorption which I feel is a lot higher than real world you gain 9.5%

edit: Thinking about it, I think DC may already take absorption into account in which case you will gain the entire 10%. I am checking on it.

 

[elle_chris]

Date: 10/13/2009 2:13:16 PM
Author: adamasgem

Date: 10/13/2009 11:45:02 AM
Author: elle_chris
Light performance and color don''t have anything to do with eachother until you get to the fancy color grades. It''s all about how the stone is cut. A D, if not well cut will look like a dud compared to a well cut J.

Unfortunately, you are dead wrong in your statement about light performance and color in your opening statement and then you correct yourself in the second and third sentances.

Ypu will always absorb some light entering and within a stone, but the cutting can either minimize or accentuate the effect.

Two examples, Richard Von Sternberg of Eightstar wears a K color EightStar which faces up like an H-I, and others here on the forum may have seen it and can verify what I say.

Optical symmetry, when combined with the proper set of crown and pavilion angles, can MINIMIZE the light path though the diamond, and therefore minimize internal absorption, such that the exiting rays are whiter than a poorer sut stone.

Conversely, manufacturers of yellow Radiant cuts, in particular, have learned how to MAXIMIZE internal absorption, and get an unusual amount of ''Lucky Vivids'' by just a little tweek in the angles.

Oops!

Will keep my mouth shut next time. But from everything I''ve read here, I never got the impression that it would affect what you''re seeing.

 

[AshNZ]

 

[Todd Gray]

Date: 10/14/2009 12:15:05 PM
Author: AshNZ
Are you annoyed at learning something new?
Ash

Actually, I''m excited. However I tend to learn better visually, can you post some examples which demonstrate the principles which you are attempting to get us to understand? The forum is not only about open discussion, but learning and teaching. Perhaps this is an opportunity for you to teach - but with a class full of people who think out loud and have lots of questions...

 

[kenny]

Also, if a ray path is longer but results in the light exiting the top of the diamond instead of going to waste by exiting out the bottom the positive far outweighs the negative.

 

[AshNZ]

Date: 10/14/2009 12:37:16 PM
Author: kenny
Also, if a ray path is longer but results in the light exiting the top of the diamond instead of going to waste by exiting out the bottom the positive far outweighs the negative.

Agreed. Which is where Karl is coming from. Just to make sure we aren''t confusing anyone though, in this case it is the reflection angles that lead to longer ray paths (bad) but position the light to exit in the correct position (very good). A case where longer ray path absorbtion is outweighed by correct light positioning

Ash