What determines brilliance vs. fire ???

[HughH]

I am in the market for a radiant cut diamond that I want to be cut as close to ideal as possible given availability and budget. Fortunately I have identified a number of stones through price scope which meet my general criteria. My challenge lies in understanding how depth and table will affect the stones brilliance, fire and dispersion.

Assuming that the stone I eventually purchase (1 to 1.5 carats) will have table and depth measurements within 5% of each other, any insight into the following questions is greatly appreciated.

1. Will a higher depth % (vs. table) result in a more brilliant stone or one with more fire/dispersion?

2. If well cut, will a higher color stone (e.g. – G/H) hold the same brilliance, fire and dispersion as a lower color stone (say D/E).

3. Why would someone prefer a brilliant stone to one with more fire or dispersion?

Thanks for your help.

 

[valeria101]

Good question!

About round brilliants, there is some sense that some sets of proportions yield more fiery or more brilliant stones, and that there is some sort of tradeoff between the two. There must be some details about this in the tutorial here and on Ideal-Scope.com (see 'BIC' and 'FIC' diamonds in these documents and a serach on the forum - there is allot to look at).

If you want to talk about other shapes, that needs taking a step back asking how 'fire' can be described as an optical effect. That, I don't think it has been touched upon much around here. I can't say I payd much attention to the interesting question because.... of a measurement problem. There are some ways to communicate brilliance online, but fire lags behind. There is some research and some models around, but overall even less mainstream than the 'technicals' about total light return.

By tradition, some cuts are more 'fiery' and there are some general observations you may find useful; you may hear that diamonds with high crown and small table show more fire or that more contrast shows more fire in one or another sort of lighting... But without much explanations behind. Of course, it is totally overkill to look at any technical research, but some find it fun and there isn't much else anyway aside looking at hundreds of diverse diamond cuts - which is basically impossible unless you work with them, as far as I can tell.

Also, the lighting conditions seem to have more to do with how fiery a stone looks than the cut itself. Of course, given the same lighting one set of proportions or shape will turn out to be consistently more fiery looking, but... the change of lighting conditions seems to have allot of impact on all shapes and, to some point, overwhelm the differences due to the optical designs of different cuts. As usual, there are extreme cases that keep their character across the usual range of lighting (from strong, uniform supermarket halogens to candle light, to patchy, multidirectional home lighting): I would expect traditional princess cuts with flat crown to be bright white and old mine cuts to be fiery whenever there is enough light to show any brilliance. But that may be just because I have't yet worked though the details or seen enough diamonds !

Just my 0.2, as usual

 

[Iceberg]

Valeria.

What''s your opinion to the fact that my newly bought diamond had a HCA score of 1.3. (excellent light return, excellent fire and excellent scintillation AND very good spread)

Would that combination offer the best of all worlds. FIRE, BRILLIANCE and SCINTILLATION ?? That is, instead of aiming strickly for Brilliance over Fire. Yes ! I know, it all depends on personnal preferences nevertheless, would it not be better to have flexibility in the visual appearance of one''s diamond. Thus the diamond reacting according to the lighting (office flood lights or dimly lit restaurant).

A penny for your thought !!

Paul

 

[HughH]

Thanks for the follow up. I am after a radiant cut which likely gets subjective as you indicate. Using the AGA charts accessed through this website as a guide, I am searching for a larger table perhaps to help position more the carat weight above the girdle vs. below thereby increasing the visual size? My uneducated assumption is that a deeper diamond within range will appear fierier than one with a larger table which I assume to be more brilliant.

 

[HughH]

Great point and I think I am open to a balance of these attributes. What I am trying to do is identify an online sourced stone that should (all things equal) should provide one or maybe all three. Sounds like you got an excellent stone. With a little luck and detective work, I hope to do the same.

Thanks

 

[valeria101]

Date: 9/12/2005 3:16:43 PM
Author:HughH

...for a radiant cut diamond

My challenge lies in understanding how depth and table will affect the stones brilliance, fire and dispersion.

Depth and table alone tell little - I would definitely not rely on just those to choose a diamond, especially if such fine details are a concern (i.e. the balance between fire / brilliance - that isn''t something table & depth will help with).



Assuming that the stone I eventually purchase (1 to 1.5 carats) will have table and depth measurements within 5% of each other

Heard that too, but I am not sure why it is important.

1. Will a higher depth % (vs. table) result in a more brilliant stone or one with more fire/dispersion?

Not sure table and depth are useful to detremine an answer here. It just so happens that this all that a GIA lab report has to say, but that does not mean that these two numbers are enough to give an answer to your question. Aside seeing the stones, I don''t know what could answer it - some cut grading tools could help, but I am not sure what amount of guess-timate is in those results. Fire is not evaluated all that well by any of the tolls I know of (IdealSCope, BrillianceScope, and computer models - for what that matters since precise measurememts of radiant cuts that such models require as input are not trivia to come by)

2. If well cut, will a higher color stone (e.g. – G/H) hold the same brilliance, fire and dispersion as a lower color stone (say D/E).

Definitely.

3. Why would someone prefer a brilliant stone to one with more fire or dispersion?

My fav color is blue, never knew why

! Same with diamonds... just a matter of taste, I guess...

Hope some of this helps.

 

[Iceberg]

Hugh ! It took me a month to find it.

Once you have established the Cut, Clarity and Colour, Finish you will want. Find the diamond form a reputable vendor. Then everytime you find one that meets YOUR criterias, passed it through the HCA grinder to see it''s score.

As Valeria indicated to you, go and read PS''s tutorials. They are very informative.

Learn before you start searching.

Kind regards,

paul

 

[valeria101]

Date: 9/12/2005 3:42:14 PM
Author: Iceberg

What's your opinion to the fact that my newly bought diamond had a HCA score of 1.3. (excellent light return, excellent fire and excellent scintillation AND very good spread)

Dunno... given that the measurements that enter into the HCA are as they are... chances are that another Sarin on the same stone will yield a HCA score of o.5 or 2.5. So, I would really not know what to say.

The various sets of 'ideal' proportions for round brilliants claim to ballance an dbrilliance. It is difficult enough to define these precisely enough to model and I don't think there is any consensus yet. Which means that the question reffers to a level of precission which I have no 'tools' to address. But that's just me and the question is probably more suitable for someone working on cut grading (Garry, Serghey, Marti Haske...). Actually, there has been some discussion about this on the forum way back leading to the conclusion that a narrow band of crown and pavilion combinations around the traditional Tolkowsky numbers give sort of balance. Takig the narrow definitions and conditions considered by the model at hand, this is correct. How realistic this is - well... No idea. There must be some truth to it, but how relevant these distinctions among H&A are and so forth are important questions that remain up to you, I am affraid.

Sorry for the confusing answer. I am not aware of any consensus beyond this.


Would that combination offer the best of all worlds. FIRE, BRILLIANCE and SCINTILLATION ?? That is, instead of aiming strickly for Brilliance over Fire.

Each diamond cut brand claims to have it!

Does it even matter? These measurements are complex enough to make 'the best' and illusive concept.

All in all, I don't think there is a 'best diamond' out there, because the appreciation of these things is basically aestethic, regardless of the technicals involved. There can be a precise quantitative description of any diamond, but the measures of 'brilliance' and 'fire' seem rather subjective. Perhaps not entirely so, just enough to make plain 'maximization' a subjective exercise too.Sorry for the simplistic approach, but asking for 'the best' leads me there - someone more experiences may have allot more interesting things to say here. This discussion reminds me of the recent british national poll for 'the best painting' out there...

Oddly enough, seeing mroe diamonds (and jewelry overall) sort of made these problem less important. In the end, it took time to develop prefferences and the technical 'best' remained a curiosity. A very entertaining curiosity (hence all these posts here) but still...

Jusy my 0.2, of course.

 

[RADIANTMAN]

Hi Hugh,

Unfortunately, there is no easy answer to your questions. Radiants are extremely complicated and cannot be judged on proportion factors alone. Ultimately, they must be seen live to be evaluated correctly. There is no substitute for your own eyes, once you have shopped around enough to know what to look for.

That being said, let me try to answer your specific questions as best I can:

1. The idea floated around pricescope that the table size on a radiant cut should be lower than the depth is an oversimplification. If you have no other information, using that formula can help you to weed out radiants with crowns that are too flat, but it is the flat crown which is the problem, not the relative size of the table and depth. There is nothing wrong with a radiant with a higher table% than depth%, as long as the crown height and angles are what they should be.

2. Lower color diamonds can sparkle just as much as higher colors, they just won't look as white. Most people think that looking whiter is better, that's why whiter diamonds cost more.

3. The only way to decide whether you prefer one kind of life to another is to look at both and let your eyes decide. There is no external standard for you to rely on. The universe of well cut radiants includes enough variation so as to accomodate differences in individual taste. Proportion factors can be employed to rule out the dogs, but they won't save you from having to see the diamonds either yourself or through the eyes of a reliable vendor. If you are relying on a vendor, remember that your taste may differ from theirs, so it still helps to look at as many live radiants as possible so you can communicate what your looking for more effectively.