what is the difference btw "brilliance" and "fire?"

[bluepetal]

Anybody know? Thanks

 

[cflutist]

Brilliance is the total amount of light (excluding dispersion) reflected from within a faceted stone and from its surface

Fire (aka Dispersion) is the spreading of white light into its spectral hues, which creates multi-colored flashes in gems.

 

[Richard Sherwood]

yep

 

[Rhino]

Date: 3/21/2005 8:14:14 PM
Author:bluepetal
Anybody know? Thanks

When seperating the components of "brilliance" and "fire" I would say it depends on the light source that the diamond is being viewed under. A general rule of thumb you must bear in mind is

a. The stonger the light source the more the diamond should function in its role as a "prism" and conversely
b. The softer the light source the more you will be able to observe the *brightness* or strength of contrast that exists in the diamond. This *brightness* is and can also be referred to as *brilliance*. Both have completely different appearances which the graphic below demonstrates (taken from our site where we discuss these elements).
c. There is an inbetween source which is ambient light in which the diamond will either give off white light reflections and if the ambient light is strong enough a soft dispersion within diamond (I''m talking cherry picked goods here).

The expression *brilliance* or *brilliant* is used in many different ways and can also mean the overall *appearance* in all light conditions. Ie. if a person is observing a diamond in direct sunlight the primary observance in those conditions will be fire, however a person may say ... gosh that diamond is "very brilliant" to describe what they''re looking at. In this way *brilliance* is used in the more general sense of the term while the way I used it above is the more particular way.

Hope that helps.

 

[Rhino]

oops... forgot the pic.

 

[Mara]

in regular ole customer terms...

brilliance is more white sparkles

fire is more colored sparkles

usually you give up a bit of one to get the other...aka more brilliant stones usually lack some fire..and vice versa.

the ideal cut stones seem to have a nice blend, but some people prefer more brilliant stones vs fiery and vice versa.

LOVE that colored sparkle image Rhino!

i think my favorite over the two is fire but i would not want to give up too much of one to get the other..in diff lighting situations i get alot of white brilliance and in others i get alot of dark colored sparkles.

 

[mdx]

Expanding on Rhino,s fine explanation. In slightly geeky terms “fire” (dispersion) can be said to be a component of brilliance. We suggest that Brilliance is made up of a number of optical processes namely

External brilliance
The reflection of light on the facet surfaces (Lustre)

Internal brilliance
Reflection and refraction of light on the pavilion facets

Dispersive brilliance
The splitting of white light into its spectral colors.
The amount of dispersion or the degree of fanning is primarily dependent on the angle of incidence of light upon the facet surface when passing into air. Hence a steeper crown angle increases fire up to a piont

Scintillation brilliance
The sparkle produced when the diamond or light source moves usually caused by changes in light incidence.
Johan

 

[Rhino]

Thanks for that additional info Johan and especially the point about *lustre* as that is often neglected and is another important component comprising the total brilliance of a diamond.

Hi Mara!

Thanks for the kudo's on the fire image! I really like that one too and I always love the layman's explanation ... sometimes even more than the geeky ones.

I'd also like to address a point you've raised....

usually you give up a bit of one to get the other...aka more brilliant stones usually lack some fire..and vice versa.

While this statement is true, it is important for the researcher to understand that there are combinations of proportions, minor facet cutting & symmetry wherein you do not have to sacrifice ANY optical element to get the other. A person can attain a diamond that has superior fire as well as superior brilliance. Of course these are much harder finds but they do exist. There are seperate optical tests which can be performed for each to confirm and demonstrate these characteristics.

Peace,

 

[Garry H (Cut Nut)]

Rhino it is impossible for the firiest diamonds to be the most brilliant.
Impossible.

You are speaking of a good compromise, but you can never have the best of both worlds. (It is a bit like marriage)

 

[oldminer]

Brilliancy is the amount of light returned from a diamond. In my definition, it is all light return.

Fire is colored light return only. In theory one assumes the diamond is colorless and then any light not colorless has been broken into spectral colors by the diamond. This spectral light is fire.

The problem is that not all diamonds are colorless. Diamonds with some degree of color return virtually no colorless light, but light that is basically tinted the color of the diamond. It is then a mater of setting an accurate threshold to only measure light of other colors that the color of the diamond. I doubt anyone is doing that.........maybe I am wrong, but we''ll see who says they adjust for body color.

Secondly, fire is VERY dependent on the types of lighting used. Fire varies according to the kind of light source. Brilliancy is something that is much more measureable and constant. Fire is a component of total brilliancy, but it is a weak element that does not set the overall look of the diamond. It can be measured, but research indicates that fire is not a component which has a direct correlation to the actual beauty or performance of a diamond. I know this may not be a popular message, but it is what we believe to be true.

People want to mindlessly maximize every aspect of light return, when the prettiest diamonds actually have many levels of brilliancy and scintillation that work very well in combination. The attribute that most defines the looks of a diamond is intensity of pattern which shows itself to the max in highly symmetric stones that happen to have excellent combinations of light return and sparkle.

I suggest you concentrate on overall light return, sparkle, and intensity. Let fire happen in certain lighting, which it will, and diminish in other lighting, which it will, no matter what you are told.

 

[Rhino]

Date: 3/22/2005 5:39:54 PM
Author: Garry H (Cut Nut)
Rhino it is impossible for the firiest diamonds to be the most brilliant.
Impossible.

You are speaking of a good compromise, but you can never have the best of both worlds. (It is a bit like marriage)

Hey Gary,

I''ve read this comment from you before but it has never made total sense to me in the way you''re describing (reflecting Mara''s comment as well). At this point in time Gary it is my conviction that you can have max results in both metrics but with very limited sets of proportion cutting. However I am not so proud that I am not teachable either. You and I are on the same page on many issues so ... enlighten me. Show me an example of a diamond that you would consider has superior brilliance at the expense of fire and vice versa. I know what I believe and my convictions on the subjects I study, but I would like to see exactly what you mean. Please do this via DiamCalc and you can email me the models and we can post them here on this thread so all can benefit from this insight. I''ll post my agreements/disagreements with your assessment and see if we can''t come to a meeting of the minds (as we have done often in the past).

Of all the issues that have arised in the past there is only 1 I know of where we differ in opinion and it is that of *contrast* as examined via DiamCalc and this one. I look forward to the correspondence.

Best regards,
Jonathan

 

[strmrdr]

From playing around with diamcalc/gemcad and other ray tracing software and my own observations I think that where the light enters and exits and what it hits in the stone has the most to do with if its returned as white or colored light than anything else.
Usualy if it hits on or near a facet junction at some point it will get returned as colored light.
If it just hits the main reflectors its retuned as white light.

A diamond with high light return has a better chance of producing fire because it is returning light sourced from more angles.
This means there is a better chance the broken up light will be returned in a usable manner.
The also makes me wonder if meet point symetry isnt more important than its given credit for. A flatened or large meet point would be more likely to window than a sharp one that bounces the light back and forth before it hits one of the main mirrors and exits the diamond.

just my 2c :}

 

[strmrdr]

Here is what I call a GOG special.
It is cut to one of Jon's favorite combos and is very very tightly cut.

Look at the pictures ignore the score for now:
image 1 - white light return from the pavilian reflectors.

image 2 - white light return and colored light return with all the facets working. The white light drowns out the colored light return but you can see it at the edges.

image 3 - colored light return centered over the LGF and the other facet junctions.

image 4 - white light return and some fire from the table.

image 5 - blasts of fire from the facet junction areas again.

image 6 - awesome contrast.

This diamond has it all :}

 

[strmrdr]

srn file for that diamond.
http://www.goodoldgold.com/sarinfiles2005/BR102DIF-13257961.srn

.gem file

http://www.goodoldgold.com/gemfiles2005/BR102DIF-GEM.gem

The rest of the data.

http://www.goodoldgold.com/1_02ct_d_if_h&a.htm

 

[Regular Guy]

Ummmmm.........though i consider myself purely in the audience here, not only do I appreciate Jonathan''s challenge, but if I''ve read here correctly, his comment matches what Paul has written elsewhere here.

Interesting reading.

 

[Garry H (Cut Nut)]

To understand why the brillianscope is a poor instrument to use for thhis analysis use this link http://www.cutstudy.com/cut/english/comp/scint1.htm and imagine one of these for each eye http://www.cutstudy.com/cut/english/comp/scint2.htm so that you can see the differenc ebetween a human perception and a camera with pre set ring lighting. Line the lights up into one of those hot ring positions and view the resultant reversed light patterns from the Bscope camera, and you will see why such instruments favor high symmetry and certain very tight parameters.
If the stone has lessor symmetry there need not be less flashes - but they will be more spread out (especially if the stone is near a sweet spot like the center of the HCA chart).

I repeat.

It is not possible to achieve maximum light return and maximum fire in the same stone.

(this is true even aside from the other factor of brightness drowning out fire)

 

[strmrdr]

Garry those pages are broke for me it says failed to load appraiser data then hangs.

 

[diamondx]

Date: 3/23/2005 7:15:30 PM
Author: strmrdr
Garry those pages are broke for me it says failed to load appraiser data then hangs.

I had the same issue using firefox. But Internet Explorer loaded it.

 

[Garry H (Cut Nut)]

I do not know why this would be so Storm - but I can not even find the place where the orignal links are on the MSU website.

I have saved and used them since 1999.

If you have problems it is worth using another computer - it is realy cool.

 

[Regular Guy]

Gary, Strorm,

Gary, thanks for this cool thing. Storm, although mine didn''t load at first, we''re likely to have had different problems, with the Google bar blocking popups in my case initially, and then needing to load some software to allow this to run.

Gary...anywhere you have written out more in long hand, for those of us not quite with it, for the really several ideas here:

- what is going on with these demos on software
- what''s the connection with the Brilliancescope, exactly
- and how this speaks to the thread''s topic of brilliance & fire

Many thanks...

 

[moolman]

To view the links Gary gave, you must allow Active X controls, most likely you are using IE, so there will be a pale yellow bar coming out on top, right click and install Active X.

 

[Garry H (Cut Nut)]

Date: 3/23/2005 9:40:16 PM
Author: Regular Guy
Gary...anywhere you have written out more in long hand, for those of us not quite with it, for the really several ideas here:

- what is going on with these demos on software
- what''s the connection with the Brilliancescope, exactly
- and how this speaks to the thread''s topic of brilliance & fire

Many thanks...

imagine a ray shining straight on the diamond from directly above - the flashes are the little spots that are shining on an imaginary screen between you and the diamond.
Like when you are on a plane and sun shines thru window on diamond.


Now imagine the reversal - the light shines from the place where a speck is - and you are top dead center. You see something like the same flash of color (- except there are threads here discussing the fact that the reversal principle is not quite that simple.)

So now imagine you place a ring of light (like the Bscope little tubular ring light - or a round fluoro tube) so that the light from it will go straight back to your single eye (or the Bscope camera lens). But what if we change the proportions ever so slightly - still lots of wonderful flashes - but the circular type patterns fall in between the positions of the Bscope 5 or 6 lighting positions - bingo - this stone is as dead as a dodo (according to the Bscope) where as it is just as beautiful as the stone where a few of the circlar patterns line up very well.

So the point is that Storms example shows that the Bscope is a useless comparison for this purpose to show high LR and high Fire.

(BTW Sergey has dropped this approach - that GIA is very heavily reliant on - because the light used should be a radiating beam - only in the airplane and sunlight are the rays that illuminate a diamond parallel rays. And we know that looking at diamond in sunlight is stoopid - see many threads on the topic.
Sergey now uses "beams" for his very advanced ETAS technology - which will not be made freely available - it is for our private usage and our cut future grading systems. It will be used with the master stone study and only those participant companies will know about it. )

 

[Regular Guy]

Garry, thanks for your indulgence. I''m thinking I''ll get it in time. For better or worse, what may seem quite arbitrary to some will stick with me, from having heard it on this site.

You know what they say...the truth shall set you free.

Here''s to Pricescope, and freedom.

 

[Garry H (Cut Nut)]

leonid, i think he has cracked the code.
Drat, we will have to kill him.

 

[Paul-Antwerp]

Date: 3/22/2005 5:39:54 PM
Author: Garry H (Cut Nut)
Rhino it is impossible for the firiest diamonds to be the most brilliant.
Impossible.

You are speaking of a good compromise, but you can never have the best of both worlds. (It is a bit like marriage)

I beg to disagree, Garry.

The concept of a trade-off between white light return and coloured light return is an old basis of gemological training, and because so many of these old ideas have been proven wrong lately, I wonder whether this particular one remains true.

Let me revert to ''garden-and-kitchen-science'': If we take it to the extreme, white light does not exist. It is a combination of different rays of coloured light, combining into a white colour. As such, a stone returning a lot of white light does not exist either, it is a stone returning enormous rays of coloured light,which combines into a white colour.

What I am trying to say is that I think that brilliance is a type of fire, just like a square is a kind of rectangle.

Live long,

 

[Antwerpman]

I will have to provide `food for thought` as I do not have any answers which can add to what has already been said.

Firstly I can understand that maximum brilliance (light return) and maximum fire (dispersion in to colours) cannot exist at the same instant as you see either `white` light or coloured light, so on this I can see your point Gary, but as Paul says, white light is in fact a combination of coloured rays, so perhaps there is a possibility that this stone which is capable of returning the maximum amount of light can also provide maximum fire through a mechanism which has not yet been identified.

Also consider the issue of contrast, it is regularly said that a stone returning only white light is not so interesting, and in fact what the human eye/brain prefers is the contrast between light and dark (Sergy`s famous checkerboard). Perhaps a similar phenomena is experienced with fire, where the stone returning the most coloured light is actually percieved as less firey than the `brilliant` stone which has a sharper contrast between white light and coloured light. In this way a stone which is theoretically `brilliant` will be percieved more favourably than one which is theoretically `firey` as the contrast between white and coloured light will be greater.

Again, as with contrast, the perception of fire will probably depend upon the viewing distance, and hence what is attractive at close range may prove less so at a distance and visa-versa. This again raises the question of human perception, and is it the case that because a model says that the light is maximally dispersed does it mean that it is true for our perception and are we as humans `tuned in` to the optimal solution or, as is often the case, do our brains carry out some computing shortcuts and leave us thinking that a sub-optimal solution is the `best` one??

How also do you address the issue of intensity of light versus the breadth of dispersion? It can be the case that light is dispersed in to very intense beams of the individual colour, but that the seperation is not sufficient for us to distinguish it, or similarly that the light is dispersed in to very wide beams of individual colour but that these loose their intensity so as to be less appealing. How do you arrive at the decision of what is the `optimal` solution of people??

Finally there is the matter of sensitivity. What is the sensitivity of the human eye to the difference between the fire in a `brilliant` stone and the fire in a `firey` stone? Perhaps it is the case that the human eye can perceive little or no difference between the fire of the two (I am assuming a very well polished or `ultimate` exa;ple in each case)

 

[strmrdr]

Something else iv noticed thats relevant here:
The relative intensity of the light can affect how the color of the light is seen by the eye.
This can be shown with the modern high brightness high end white LED''s.
Because of how they work there is always a blue tint to the light.
Shine it on a white surface in a dark area.
With the led close to the object the light appears white but if you move the light farther away the blue tint becomes more apparent as the intensity is reduced by the distance.

Could it be that bright flashes of fire are more likely to be seen as white light return by the eye vs less bright fire?

 

[strmrdr]

Actually I just came up with another proof.
Take a uniform colored object in bright light.
Partially block the light to one part of the object the 2 parts of the object will have different apparent colors as seen by the eye with the brighter section looking lighter in color.
Bright light washes out perceived color.

 

[strmrdr]

Date: 3/23/2005 10

4:28 PM
Author: Garry H (Cut Nut)

Date: 3/23/2005 9:40:16 PM

So now imagine you place a ring of light (like the Bscope little tubular ring light - or a round fluoro tube) so that the light from it will go straight back to your single eye (or the Bscope camera lens). But what if we change the proportions ever so slightly - still lots of wonderful flashes - but the circular type patterns fall in between the positions of the Bscope 5 or 6 lighting positions - bingo - this stone is as dead as a dodo (according to the Bscope) where as it is just as beautiful as the stone where a few of the circlar patterns line up very well.

Isnt the difference between a high performance diamond and a lesser performance diamond in how well they return light in a usable manner regardless of the lighting position?
A lopsided princess cut diamond comes to mind.
With light from one side it might perform with the best with a lot of return but with the light on the other side it is dead looking.