60:60 vs Ideal MRB proportions – Is beauty in the eye of the beholder? Can one cut fit all?

[Texas Leaguer]

David,
You are introducing confusion into the topic in a several ways. You are presenting a false-choice argument by suggesting that to make a fiery diamond you have to sacrifice scintillation.
What do you mean by "the 60/60 80lgf 'scintillation' stone"? What is your method for assessing scintillation? Are you suggesting that a fiery ideal cut cannot also have great scintillation?
Your last line suggests a sort of 2 for one exchange, as though if you want fire you have to give up scintillation and spread!
Lastly you talk as if there is a profound difference in spread, whereas in a 1ct stone the difference between most ideal cuts and most spready 60/60s would only be one tenth of a millimeter.

 

[flyingpig]

I was just wondering - if 60/60 gives more spread (within reason, ref: Garry's post above) but less fire, is it simply the case that the cut needs to be modified to give larger/shorter/fatter pavilion mains? which would increase dispersion and help balance any reduction in fire from the 60/60 proportions?

Great post shiny
Personal question......if I may.....have you seen fire in a diamond? If so, can you please describe your experience?
I ask because the point about actual facet size seems to get buried.
Plus, what we're speaking of is balance.
So if one does not have personal experience with fire, it could be easily given too much preference in the balance.
Put another way, the 60/60 80LGF "scintillatioin" stone might have less fire....but
1) what if fire is not the primary goal?
2) what if the additional spead and scintillation are more attractive as properties, as compared to fire.
Who says fire is better than scintillation and spread?

Why not?? It is amazing.

The last diamond. tb59.2/33.6ca/41.0pa with 76 lower.

https://www.goodoldgold.com/diamond...S-H-SI1-diamond-stock-14877-cert-104054933001

Too bad.. trade members cannot comment on this diamond..

 

[pyramid]

The stone on the right is a 2 and half carat whereas the others are smaller diamond weights. Need to see 60/60 next an ideal cut of the same weight because as David is saying larger facets give more fire.

 

[Rockdiamond]

David,
You are introducing confusion into the topic in a several ways. You are presenting a false-choice argument by suggesting that to make a fiery diamond you have to sacrifice scintillation.
What do you mean by "the 60/60 80lgf 'scintillation' stone"? What is your method for assessing scintillation? Are you suggesting that a fiery ideal cut cannot also have great scintillation?
Your last line suggests a sort of 2 for one exchange, as though if you want fire you have to give up scintillation and spread!
Lastly you talk as if there is a profound difference in spread, whereas in a 1ct stone the difference between most ideal cuts and most spready 60/60s would only be one tenth of a millimeter.

Hi Bryan,
Thanks for raising the points you have.
You're correct I was too vague.
I should not assume that the type of stone I'm thinking of "60/60 80LGF" is a good workable description.
To clarify: A longer LGF combined with other factors to produce less contrast. You won't see hearts and arrows patterning- instead, you a less organized sparkling effect.
Scintillation.
At this point in time, I do not believe there's an accurate method for measuring scintillation.
I would also bring up my oft repeated point about fire, and facet size.
That is to say, measuring fire independent of facet size- and not related to other diamond cuts- from my perspective, is confusing the issue.
What about a comparison of actual fire events in two diamonds cut to the same proportions , one 4 ct, the other .50ct.
Let's also measure fire for fire between an OMB and a RBC, same carat weight. If fire is a main goal.
I'm not denying that fire is amazing- or even that a super ideal is successfully cut to produce more fire than the type of stone I'm thinking of.
We're also in agreement that a percentage of buyers place a high priority on fire.
However, there's also many buyers that would choose that extra .1mm.
And many of them are also picking based on real life light performance- IOW, they are buying a well cut diamond based on how it looks.
I think we're really on the same page in many ways Bryan.
I've never argued that Super Ideal cuts are bad in any way- and I understand why they are worth the price.
Have you never had a buyer choose a slightly spreadier stone based on the way it looks?
The balance I find missing is that the vocal cut fanatics can sometimes drown out the more moderate, balanced views on this.
Cut is important- super important- but there's many more potential winners out there than the narrow guidelines we see here.

 

[flyingpig]

The stone on the right is a 2 and half carat whereas the others are smaller diamond weights. Need to see 60/60 next an ideal cut of the same weight because as David is saying larger facets give more fire.

Correct, larger diamonds have larger facets and give bigger fire. RD suggests 60/60 with 80 lgf for less fire, but for more spread and scintillation.
My response to that is 60/60 style with 76 lgf is beautiful and viable, as shiny suggested.
Larger diamond, larger facets, larger fire. Add shorter lgf to compensate any deduction in dispersion and fire due to large table. Add even broader fire. Fantastic.

I am posting this video to just show what a 60/60 with 76 lgf looks like.
The video just happens to compare a super ideal cut diamond and a 60/60 style diamond.

 

[pyramid]

To my eyes single cuts give off the best scintillation, these have only 16 facets. No or not much fire though. So is scintillation the opposite of fire really? Does scintillation come from brilliance which we all know is the opposite of fire with the fic and tic cuts being opposite in Garry Holloway's HCA?

 

[Karl_K]

Correct, larger diamonds have larger facets and give bigger fire.

It is far more complicated than that and the variable is lighting.
There is lighting where smaller VFs return far brighter and "better" fire than large facets. Look in the fire thread here on PS and see where the fire is at. In almost every case it will be from the crown facets not the table where the largest virtual facets live.
There is also a point of diminished returns where the fire events are large but to few.
Fire to even begin to talk in depth about it would take 10000 words there are just so many variables.

 

[Karl_K]

To my eyes single cuts give off the best scintillation, these have only 16 facets. No or not much fire though. So is scintillation the opposite of fire really? Does scintillation come from brilliance which we all know is the opposite of fire with the fic and tic cuts being opposite in Garry Holloway's HCA?

Fire is part of scintillation when the diamond, viewer or light source is moving.
In general the Davids "scintillation diamonds", which is really a silly term, with small virtual facets need bright small source light to produce fire.
Where for example a well cut oec can produce fire in much flatter lighting with large light sources.

 

[msop04]

A few questions...

I read that GIA rounds LGF to the nearest 5%... Is there any way to know what the actual LGF is without having AGS grade it? The reason I ask is because both of my diamonds had LGF listed as 80%, but my older diamond had more "splintery" arrows than my latest stone, which has noticeably fatter arrows (looks much more like 75% than 80% to me).

Can a diamond's LGF be recut to make the arrows fatter? For the cutters and those in the know about recutting... IF a recut for fatter arrows (70-75%) is possible, do you think my stone would my stone be a candidate for such recutting? Also, would there be any visual change to the stone besides thicker arrows? Forgive me if this has already been answered, as I couldn't find it in a search.

 

[Karl_K]

To even discuss fire without discussing lighting shows that the person talking lacks a fundamental basic understanding of fire in the first place.

Fire in diamonds in my opinion is best discussed in how often across a wide array of lighting and environments fire is observed.

 

[Karl_K]

A few questions...

I read that GIA rounds LGF to the nearest 5%... Is there any way to know what the actual LGF is without having AGS grade it? The reason I ask is because both of my diamonds had LGF listed as 80%, but my older diamond had more "splintery" arrows than my latest stone, which has noticeably fatter arrows (looks much more like 75% than 80% to me).

Can a diamond's LGF be recut to make the arrows fatter? For the cutters and those in the know about recutting... IF a recut for fatter arrows (70-75%) is possible, do you think my stone would my stone be a candidate for such recutting? Also, would there be any visual change to the stone besides thicker arrows? Forgive me if this has already been answered, as I couldn't find it in a search.

GIA rounding to the nearest 5% is totally ridiculous.
Different angle combinations react differently to different lgf%.
Some combos will show a large difference from lets say 77 to 80 where others will show little to no difference.
Recutting for a different lgf% is not practical.

edit: a scanner can be used to get the actual lgf%.

 

[msop04]

GIA rounding to the nearest 5% is totally ridiculous.
Different angle combinations react differently to different lgf%.
Some combos will show a large difference from lets say 77 to 80 where others will show little to no difference.
Recutting for a different lgf% is not practical.

Thanks for answering, Karl. That makes a lot of sense in regards to the big difference in the look of my diamonds. Any idea why GIA rounds that way??

 

[pyramid]

I see that fire colours move into the different arrays but they don't seem to go on and off as quickly as white sparkles do to me? I thought that was scintillation. Fire seems slower as it moves across different colours but sparkle seems to shut on and off from bright white to nothing in that space and then bright white from another area of the diamond, meaning it goes all over the diamond leaving largish spaces in between whereas we can't see that with fire it just takes over and comes out slowly like smoke kind off and when it shines from another area it doesn't seem as connected to the first as there may be some other colour or colour still there. I feel sparkle is like a string of lights which sparkle on and off but come back again to the same bulbs lighting them up in the same or near same places. Sparkle is like a star shape but fire is like a flame shape.

 

[pyramid]

So Kark_K, you reckon it is to do with lighting. Well maybe ALL OF cut has to do with lighting too then. There is never an ugly diamond when it shines in the sunlight. As long as the diamond has the correct depth so it does not have a fish eye or is a nail head, then they all are beautiful if cut to nice proportions and not too chunky on the crown with a table no more than 60.
Maybe it is just a case of fine tuning the different facets for different looks but the outline shape of the diamond as long as it is pleasant to the eye doesn't matter what it's angles are. Then we would get different looks like the old cuts give e.g. old mine cut and oec, and transitional, they all had different outlines but look beautiful in their own right. So diamonds maybe should not be cut to ideal but to shape in the same way fancy cuts are.

I often wonder why so many jewellers and diamond cutters do not worry about cut to the extent this board does, I now there are different price points but lots of diamonds especially in the Very Good cut range are good enough for most people. I always think this ideal cut is just to mask lower color diamonds in order to sell them. In antique cuts they don't do this but the larger chunky facets show more brilliance so hide colour and some even love them way down to the O color range to evoke an air of yesteryear. If those chunky facets show more white light, we are always being told that color does not show the same in older cuts, then maybe it does emit more colored light/fire as David has said. Well we certainly can see lots of colors in the Old European Cuts, where fire seems to cover the whole facet rather than just jump out like a flame in the Round Brilliants. The facets on OEC's with the colors look like a mosaic pattern of different colors.

Wouldn't it be great if there were lots of different artistic looks to choose from, like 100 looks instead of just something like 4 rounds. I know the extra facets on some of the cuts are said to just make them busier and some prefer this, there must be other looks not discovered yet. Like the OEC has a flower. Not just like geometric repeat shapes like flowers and petals but something like an oblong which is showing in different places of the diamond or a face even of your loved one. Can diamond laser cutting do things like this, engraving patterns would look good on diamonds or leaf patterns.

 

[Rockdiamond]

To my eyes single cuts give off the best scintillation, these have only 16 facets. No or not much fire though. So is scintillation the opposite of fire really? Does scintillation come from brilliance which we all know is the opposite of fire with the fic and tic cuts being opposite in Garry Holloway's HCA?

I think your post highlights an issue pyramid.
Sometimes we use terms that we understand- but other people have a different concept.
I love single cuts ( known as 8/8 in the trade).
But to my eye, they offer less scintillation than a brilliant cut diamonds.
This indicates to me that we are thinking of a different effect

 

[Rockdiamond]

To even discuss fire without discussing lighting shows that the person talking lacks a fundamental basic understanding of fire in the first place.

Fire in diamonds in my opinion is best discussed in how often across a wide array of lighting and environments fire is observed.

We're in total agreement on this Karl.
I find that fire is discussed here on PS as an absolute. But of course, it's not. So many factors go into how we perceive fire.
Spread, on the other hand, is a hard number.

I often wonder why so many jewellers and diamond cutters do not worry about cut to the extent this board does

Another excellent point.
In terms of sellers- at the point of sale, most sellers only want to close the sale.
This does lead to some of the bad stories we've heard. Using any sort of BS to close a sale.
But on the other side, sellers that are so committed to one particular "brand" they can't seem to enjoy or emphasize the advantages to other brands or styles.
Discussion of fire as it's own "thing" goes to that end IMO.

 

[Texas Leaguer]

To a couple of Karl's points:
It is important in this discussion to understand that fire is a component of scintillation, as Karl stated. Scintillation is the turning on and off of facets in response to motion of observer, diamond, or light source. It is composed of flash scintillation and fire scintillation.

While understanding fire is, on the one hand, complicated by the almost infinite number of lighting environments in real world scenarios, it is possible to mathematically model it for comparison purposes. Diamonds, depending on their cut parameters, will vary in their intrinsic potential to exhibit fire when viewed in a favorable lighting environment.

And it is possible to visually compare different makes for their ability to produce fire by capturing video taken in specially controlled lighting environments that accentuate fire. Such videos also display the overall scintillation pattern of the stones being compared.

 

[Texas Leaguer]

Too bad.. trade members cannot comment on this diamond..

Just to be clear about forum policy, trade members ARE allowed to comment on vendor stones for educational purposes. But cannot criticize or recommend them.

 

[Rockdiamond]

Bryan, we're combining "mathematical models" and "intrinsic potential"
To me, this means the mathematical model is just taking a stab at what might be. it will depend on lighting and other factors.
Even so, can you provide a comparison between two stones of same cut, different ct weights?

In terms of the rotating videos, I disagree.
They have value, without a doubt, but not so much for real world fire, and scintillation.
People never rotate diamonds in a perfectly symmetrical pattern and the lighting in the boxes taking the rotating video needs to be far more stable/ repeatable than real world lighting.
I view them as more "glamor" shots.

 

[Karl_K]

While understanding fire is, on the one hand, complicated by the almost infinite number of lighting environments in real world scenarios, it is possible to mathematically model it for comparison purposes. Diamonds, depending on their cut parameters, will vary in their intrinsic potential to exhibit fire when viewed in a favorable lighting environment.

And it is possible to visually compare different makes for their ability to produce fire by capturing video taken in specially controlled lighting environments that accentuate fire. Such videos also display the overall scintillation pattern of the stones being compared.

I must respectfully disagree.
Both video and math have the same problem.
To many variables.
There is no fire metric that works, there is no fire video method that is highly relevant to what someone will see in person.

Don't get me wrong, I love video done right it is the best way to remotely show at least something of the personality of a diamond.

 

[Texas Leaguer]

Intrinsic potential - think of two stones in a dark room, one well cut and one terribly cut. The well cut stone has intrinsic potential to be very brilliant. But until light is made available neither stone can exhibit its potential (or lack thereof).

With the right lighting environment, you can compare various aspects of performance between the two.

A rotating video puts the stones being compared through the exact same motion relative to a common lighting environment , so you can make apples to apples comparisons.

Such comparisons can be used as visual demonstrations of the computer modeling.

 

[Karl_K]

Spread, on the other hand, is a hard number.

Visual spread, how a diamonds spread appears to the eye is far from a hard number.
Some variables, lighting, distance, edge to edge brightness, contrast to the environment, viewing angle, lighting angle, 3d effect, relative size to a reference.
For example,
A diamond is going to look bigger on a size 2 finger than my size 14 fingers.

 

[Texas Leaguer]

There is no fire metric that works, there is no fire video method that is highly relevant to what someone will see in person.
Don't get me wrong, I love video done right it is the best way to remotely show at least something of the personality of a diamond.

I agree with the bolded, but with an important qualifier.
A 'fire video' is not actually what an observer is likely to see in the real world. That is, the fire has been dialed up and the brightness dialed down to be able to see the effect and compare the effect between to samples. It is a little like putting on polarized glasses to look down into the water to see the fish.
You have to extrapolate that to the real world, but the relative performance is what you are testing, and that has validity.
With regard to fire, differences are in the frequency and size of the chromatic flares. If you know that one stone is likely to trigger more and/or bigger fire events than another, you may prefer that stone depending on how it compares in other aspects. The key in all of this is to be able to understand the tradeoffs and choose the stone right for you.

 

[Rockdiamond]

Visual spread, how a diamonds spread appears to the eye is far from a hard number.
Some variables, lighting, distance, edge to edge brightness, contrast to the environment, viewing angle, lighting angle, 3d effect, relative size to a reference.
For example,
A diamond is going to look bigger on a size 2 finger than my size 14 fingers.

Look at it this way Karl- a well cut diamond measuring a 7mm is always going to look bigger than a 6mm well cut diamond when they're compared next to each other. No matter who's wearing them.
We can compare two 7mm diamonds, and debate which looks larger, due to differences in cut. But the physical measurements are the ONLY totally objective measurements of diamond.

That's why I have an issue with the scientific value of mathematical modeling of light performance.
It's theoretical- and open to interpretation.
MM measurements are hard cold facts- can't be interpreted differently.

PS- my ring finger is a 15- so there.

 

[Rockdiamond]

I agree with the bolded, but with an important qualifier.
A 'fire video' is not actually what an observer is likely to see in the real world. That is, the fire has been dialed up and the brightness dialed down to be able to see the effect and compare the effect between to samples. It is a little like putting on polarized glasses to look down into the water to see the fish.
You have to extrapolate that to the real world, but the relative performance is what you are testing, and that has validity.
With regard to fire, differences are in the frequency and size of the chromatic flares. If you know that one stone is likely to trigger more and/or bigger fire events than another, you may prefer that stone depending on how it compares in other aspects. The key in all of this is to be able to understand the tradeoffs and choose the stone right for you.

First- my compliments on your pics/videos- no criticism intended.
Any picture/video is far more realistic to the person who shot it, or was involved in the shooting and knows the subject.
My personal feeling is that fire videos are indeed useful. But not in a scientific comparison sort of way.
I'm proud of my pics for their ability to transmit what I see- but they're in no way scientific.
I can easily stimulate fire for a pic.
Then there's the magnification - of course, a necessity to show details.
But going back to my oft flogged point about the percieveable fire, and actual facet size.
The fire we can generate in a .50ct diamond, using macro photography is far more than would be easily visible to the naked eye.
But it would look similar to the fire in macro vid of a 5ct- which would have far greater fire potential in real life.

 

[gm89uk]

But not if they were recorded simultaneously next to each other at the same magnification

 

[pyramid]

Think I have confused sparkle with flash scintillation. I still think flash scintillation is more noticeable and faster than fire. I think larger spread diamonds have far more flash scintillation than fire scintillation but it is just as good in a different way. So their should be two flavours of diamonds, the 60/60 which is how we always had diamonds over in the UK. The ideal cut diamonds are more the American cut with the smaller table and it has taken over on the internet. A diamond which flashes white looks totally different from ideal cut diamonds showing lots of fire, narrower crowns as someone wrote in an article, pencil shaped crowns. It may be different when the diamonds are precision cut but buying smaller diamonds uncarted type from jewellers over here, the flash scintillation is preferrable I would say.

 

[pyramid]

In a previous job a woman and her boyfriend went to New York and got engaged there. The diamond was bezel set. I remember seeing the diamond from across the room and thinking it looks different from other stones but there was still something hypnotic about it to me. It was larger than average, maybe about 75 ponts, it was not G color maybe I would say now, an I color, but what I noticed most is we did not really see the light coming from within the diamond, the diamond had a large table and it was the glare that was coming off it and flashing around the room. I don't know if there was maybe some white light return from within but no fire (coloured light) at all. Yet there was another lady who wore an old cut diamond, I know that now but then I just knew it had a very tall crown, must have been an old mine cut as tall and steep much steeper than OEC. Her diamond showed off coloured light in large amounts especially with the sun coming in the window.

This other diamond though with no coloured light and what I would say was mostly glare off the surface looked different but just as good, in a way I liked it better. Now nobody commented on either of the rings but we are in the UK and people really only comment on a style of ring and not the diamond. I think people hear just prefer a twinkle or two so may prefer worse cut stones.

 

[Texas Leaguer]

A little electromagnetic levity for a Wednesday morning - a tweet today from Neil DeGrasse Tyson:

Geeky Humor: Photon checks into a hotel. Bellhop asks, "You have any luggage?" The Photon replies, "No, I'm traveling light!"

 

[Garry H (Cut Nut)]

Sorry - I left out Brian's quote

I must respectfully disagree.
Both video and math have the same problem.
To many variables.
There is no fire metric that works, there is no fire video method that is highly relevant to what someone will see in person.

Don't get me wrong, I love video done right it is the best way to remotely show at least something of the personality of a diamond.

I think you are both right, and Sergey et al are working on it and building an excellent model to test in the real world. Here is a summary of some of the content in our 2013 article:

Scintillation is quick bright flashes that appear and disappear quickly. It can only be seen as a diamond moves when lit by relatively small bright lights. Brilliance (and fire) can be seen in diamonds illuminated by large dim lights, and small bright ones.

Scintillating flashes (‘bloom’ and ‘star’ effects) can extend beyond facet edges or even past the edges of a diamond. Nearly twice as much scintillation is seen with both eyes than one, and in a 3D stereo diamond video rather than mono.


Fire is separate coloured flashes characterized by brightness, saturation, size, shape, lifetime (duration) and colour gradient. Coloured fire flashes can also have ‘bloom’ and ‘star’ optical effects. Fire flashes can be slower like brilliance flashes, need not be very bright, and can originate from both small bright lights as well as large relatively dim lights.