Brilliance vs. Fire Larger Tables/Smaller Tables

[Colored Gemstone Nut]

Hello to the cut nuts,

I am working my way through understanding cut and the differences in crown/pavillion angle vs. different table sizes and the affect it has on brilliance vs. fire.

As I understand it a stone with a larger table will have more brilliance, but less fire...

Question Number #1:

Does the stone have more fire with a smaller table because the crown facets are optimized and larger vs. a stone with a larger table and smaller crown facets. Is this one of the main factors that affects the way fire is observed by the viewer as seen through the crown facets being that the table is smaller so the crown facets are bigger?

Question #2:
In understanding brilliance in a stone with a larger table does the larger table minimize the fire observed because the crown facets are smaller?

Question #3:
Is brilliance increased because it is defined by the light being shot through the table of the diamond as reflected off the pavillion facets and since the table is bigger more of that light gets through?.

I know people prefer different looks, but was wondering if the crown and pavillion facets measured the same in 2 seperate diamonds with one having a small table and one having a large table is my reasoning correct in understanding why brilliance is increased in diamonds with larger tables and why fire is increased with diamonds with smaller tables.

I know there is much more that might affect these factors in the balance of light being returned to the viewers eye but was wondering if my conclusions to what I have read are right as far as how the larger and smaller tables play on fire and brilliance and why being the crown and pav angles were the same in both diamonds...??

-Josh Rioux
Sitka, Alaska

 

[Garry H (Cut Nut)]

It is not too hard Scorpion.

Light entering a diamond at very oblique angles is more dispersed than light entering at 90 degrees. But most is reflected (62% is reflected at 5 degrees or 85 degrees angle of incidence).
If you have the Dark Side of the Moon from pink floyd then look at the cover.

Light exiting a diamond can only escape (partially - not all the light ever escapes) if the angle of incidence (from the perpendicular) is less than 24.5 degrees. The closer it is to this CRITICAL ANGLE the more the light rays will be dispersed into their individual wave lengths. Therefore the light exits close to parallel to the diamonds surface.

So in order to see the fire emerging from the table you need to look side on to the diamond. Not much value!
But the crown facets can direct that light back toward a face up viewer. so it is not that the table does not produce fire - it just produces use-less fire.

So more crown = more fire.
So steeper crown = more fire.
It really is not just that simple though, because there are ideal optimums for reducing leakage etc.

Sergey where is link to your www.cutstudy.com explanation as to why we do not see green and other more advanced issues about fire - i could not find it?
The more

 

[Colored Gemstone Nut]

Sergey/Garry-
In understanding the way critical angles and a diamond handles light I have been wondering about a visual representation of how a stone might look if the ray of light is traced. The light entering the stone and then graphed where it is reflected and exits based on measurements. Does the Diamoncalc program show the path of light rays entering and exiting a diamond based on the sarin measurements entered. I think a way to learn to is to enter different data and see how it effects how the light enters and exits the stones based on a visual representation. I was just wondering if diamond calc did this too...

-Josh

 

[Garry H (Cut Nut)]

Yes it does.
And you should at least download the free version (www.ideal-scope.com or links on pricescope etc) - really if you are buying books etc - this program at $280 is far more instructive and usefull.

The other part of your request has been availabvle free for 4 years at http://www.cutstudy.com/cut/english/comp/scint1.htm

 

[Colored Gemstone Nut]

----------------
On 9/3/2003 10:18:26 PM Cut Nut wrote:

Yes it does.
And you should at least download the free version (www.ideal-scope.com or links on pricescope etc) - really if you are buying books etc - this program at $280 is far more instructive and usefull.

The other part of your request has been availabvle free for 4 years at http://www.cutstudy.com/cut/english/comp/scint1.htm
----------------

As always Garry..Thank You...and for referencing the article...

Warm Regards...

-Josh

 

[Rhino]

Hey bossman,

My kind of question.

Scroll on down.


----------------
On 9/3/2003 12:28:50 AM scorpion wrote:
Hello to the cut nuts,

I am working my way through understanding cut and the differences in crown/pavillion angle vs. different table sizes and the affect it has on brilliance vs. fire.

As I understand it a stone with a larger table will have more brilliance, but less fire...

Question Number #1:

Does the stone have more fire with a smaller table because the crown facets are optimized and larger vs. a stone with a larger table and smaller crown facets. Is this one of the main factors that affects the way fire is observed by the viewer as seen through the crown facets being that the table is smaller so the crown facets are bigger?

Yes. Also you have to consider that overall brilliance includes not only refracted light from within but also reflected light off the facet surfaces. Larger tables add a big splash (if you will) of reflected light which is generally ONLY white light return. Fire and dispersion happens from within and are primarily observed under direct light and ambient light conditions (moreso or stronger in direct). When tables are smaller there is less of an emphasis of any reflected light while there is more in refracted light. That is of course assuming a cherry combination of crown and pavilion angles and further tweaking of overall brilliance, fire and scintillation can also be acheived by tweaking the minor facets in a certain manner too.

Question #2:
In understanding brilliance in a stone with a larger table does the larger table minimize the fire observed because the crown facets are smaller?

You can have strong fire in a diamond with a larger table as long as the crown pavilion combo is right on. A larger table can contribute to more leakage though. If you review some of the Regent diamonds their crown/pavilion combo's are right on but some have rather large tables (though smaller than the Queen of Hearts) and the result of the larger table is a ring of leakage under the table. Even at that though Regent cut diamonds transmit more light at the high angle than any other fancy cut which is why they are one of the only fancy diamonds on the market that have brilliance comparable to the best rounds.

Question #3:
Is brilliance increased because it is defined by the light being shot through the table of the diamond as reflected off the pavillion facets and since the table is bigger more of that light gets through?.

Not necessarily. Gary covered this in his answer.

I know people prefer different looks, but was wondering if the crown and pavillion facets measured the same in 2 seperate diamonds with one having a small table and one having a large table is my reasoning correct in understanding why brilliance is increased in diamonds with larger tables and why fire is increased with diamonds with smaller tables.

There is both a negative and positive aspect to the larger table thing.

The negative aspect is that the larger table will produce that "ring" of leakage otherwise known as the ring of death.

In rounds it is dreadful and can make the stone look dull under the table.

The positive aspect (if you wanted to consider this positive) is the larger table will produce that larger area of reflected "flash" off of the table when light is bouncing off the facet surfaces (particularly the table).

I'll tell ya something funny (well it isn't so funny when you think about it) but people I knew who worked in a dept store used to find the light reflecting off the table as they aimed the diamond at the prospective clients and when they talked about how "sparkly" their diamonds were would aim that bright white reflection RIGHT INTO THE CUSTOMER'S EYESb which of course led them to believe it was one of the most brilliant diamonds they ever laid eyes on. A deceptive trick but having a large table on the diamond made it easy to find the large reflection off the table to shine in their faces.

Another thought to the "more fire" aspect of larger crown facets/smaller tables. Diamonds with shallow crowns and larger tables have less distance to travel for it to exit the diamond. Less distance = less time for the light to break up into it's spectrum. More crown, more substance for the light to travel through, the more time and distance it has to break down into it's spectral colors thus returning more FIRE to the observer.

BTW ... Gary we just purchased the Dark Side of the Moon DVD (the making of it) and got a kick out of your example. Floyd ROCKS!

Rhino

I know there is much more that might affect these factors in the balance of light being returned to the viewers eye but was wondering if my conclusions to what I have read are right as far as how the larger and smaller tables play on fire and brilliance and why being the crown and pav angles were the same in both diamonds...??

-Josh Rioux
Sitka, Alaska

----------------

 

[Rhino]

Josh,

I'm in the process of updating our BrillianceScope tutorial. You may want to check that out as it covers some new and interesting stuff concerning the breakup of light within a diamond into it's spectrum.

Rhino

 

[Serg]

----------------
On 9/3/2003 3:56:39 PM Cut Nut wrote:



Sergey where is link to your www.cutstudy.com explanation as to why we do not see green and other more advanced issues about fire - i could not find it?
The more
----------------

https://www.cutstudy.com/cut/english/grading1/fig3.htm

https://www.cutstudy.com/cut/english/grading1/4.htm

https://www.cutstudy.com/cut/english/grading1/5.htm
https://www.cutstudy.com/cut/english/grading1/6.htm
----- Original Message -----