When do we get fire? Why is it sometimes pastel?

[Rockdiamond]

Who defines "Ideal Optics"?

 

[Rockdiamond]

Interesting discussion Kenny. I think you have hit on many of the key aspects, but as Karl explains it is very complex and ever changing. I think that is what makes fire the most magical aspect of diamond light performance.

Here's a basic observation that I don't know if anyone has mentioned yet. In pictures taken in the real world, well cut diamonds are reflecting various things in the environment including contrasty areas as well as colorful areas. Therefore it is easy to mistake some colored reflections in these pictures (and sometimes in real life) for dispersive color (fire).

There are all kinds of things (light source(s), diamond, environment, observer) that can impact the appearance of fire, how likely it is to be observed, how big the colored sparkles are,and how saturated various hues appear. (An unsaturated hue is essentially a pastel). Color mixing is a possibility both in dispersion on top of reflected color, as well as (I believe) mixing of two dispersive colors on a virtual facet.

I completely agree with Bryan's statement.
In taking pictures- or in real life, the slightest movement will produce, or remove the prism effect we're referring to as fire.


I also feel that attributing it to "Ideal Optics" is an incorrect correlation- no matter who is declaring a stone has "ideal optics"

 

[Rhino]

Who defines "Ideal Optics"?

AGS

 

[MelisendeDiamonds]

a. ideal optics
c. since diamonds with ideal optics are the best at capturing and reflecting back the surrounding environment you are also seeing reflections of colors within that environment

'Ideal optics" in a round brilliant at least what is marketed on Pricescope as "Ideal H&A" as ideal is not optimized for fire not even close. 34.5/40.8/77 A "Tolk Ideal" is balanced with good brightness and fire, brightness is favoured over fire.

Other combinations can produce more fire at the expense of brightness.

Most fire from Round Brilliant is seen in the arrows, it is caused by clipping not by dispersion.
Part of white light is "clipped" making the arrows colored.

Larger VFs allow more chance for clipping and greater seperation of colors allowing the observance of more fire.

 

[Rockdiamond]

thanks Jon- since this an objective discussion, can we use the term "Ideal Optics as defined by AGSL".
It's a proprietary term- like a brand name, as opposed to some sort of scientific description.

Can we agree that other stones, not termed "Ideal" by AGSL will also exhibit fire- In fact, some large faceted shallow diamonds- clearly not termed "ideal" by AGSL may exhibit MORE fire if the facet placement, size and lighting sources are aligned.

I love AGSL Ideal stones- but I do think there's times that aspects attributed "Ideal" optics, as defined by AGSL are overstated.

 

[MelisendeDiamonds]

thanks Jon- since this an objective discussion, can we use the term "Ideal Optics as defined by AGSL

Since when was this ever an objective discussion when the term "ideal" is used.

Vendor A, I sell ideal H&A "Superideal" diamonds. Tolk says they are ideal so does AGSL. To get the best fire you need a "Superideal" cut.

Vendor B, I sell high spread diamonds with "Personality" and low contrast pattern to me these are "Ideal Cut" so don't you call AGSL diamond the only "Ideals" you have to specify its according to them, not a fact. What I sell is plenty beautiful and has great fire.

How many times does this same tired argument have to be repeated?

 

[diagem]

thanks Jon- since this an objective discussion, can we use the term "Ideal Optics as defined by AGSL".
It's a proprietary term- like a brand name, as opposed to some sort of scientific description.

Can we agree that other stones, not termed "Ideal" by AGSL will also exhibit fire- In fact, some large faceted shallow diamonds- clearly not termed "ideal" by AGSL may exhibit MORE fire if the facet placement, size and lighting sources are aligned.

I love AGSL Ideal stones- but I do think there's times that aspects attributed "Ideal" optics, as defined by AGSL are overstated.

David, AGSL is named here due to their system identified with the term "Ideal"
Do other cuts exhibit fire (e.g. Small,medium,large,X-Large etc..)? Sure they do, and they are potentially beautiful as well.

But...,

We are not talking "specifically" rounds are we...

When we cut to Ideal optics, we are able to control the sizes of the VF we design so we can control fire effect...

In random generic cuts, no matter how beautiful, the fire and other optical properties are not controlled as designed cuts are...

We attribute AGSL's "Ideal" term here because they are the authority on cut at the moment....

 

[Rockdiamond]

Interesting point Haroutioun.
Putting things in a slightly different perspective- I honestly believe that the ideas about each stone by many of the participants here are based on a belief in the stones and the way they "perform". I don't see the discussion about competing sales pitches. It's about different ways to look at, and judge diamonds.

But point well taken- it's very difficult for some of the most seasoned players to remove all commercial aspects from their statements.

 

[Rockdiamond]

thanks Jon- since this an objective discussion, can we use the term "Ideal Optics as defined by AGSL".
It's a proprietary term- like a brand name, as opposed to some sort of scientific description.

Can we agree that other stones, not termed "Ideal" by AGSL will also exhibit fire- In fact, some large faceted shallow diamonds- clearly not termed "ideal" by AGSL may exhibit MORE fire if the facet placement, size and lighting sources are aligned.

I love AGSL Ideal stones- but I do think there's times that aspects attributed "Ideal" optics, as defined by AGSL are overstated.

David, AGSL is named here due to their system identified with the term "Ideal"
Do other cuts exhibit fire (e.g. Small,medium,large,X-Large etc..)? Sure they do, and they are potentially beautiful as well.

But...,

We are not talking "specifically" rounds are we...

When we cut to Ideal optics, we are able to control the sizes of the VF we design so we can control fire effect...

In random generic cuts, no matter how beautiful, the fire and other optical properties are not controlled as designed cuts are...

We attribute AGSL's "Ideal" term here because they are the authority on cut at the moment....

Hi Yoram!
We do see a few aspects differently- and it's a subject we never tire of discussing.
Putting everything else aside- I strongly disagree with the part in bold.
The thread is about fire- no mention of fire in AGSL graded stones i the title.
If we are comparing GIA and AGSL, we'd have a discussion about which lab has more authority- and I can see a very good case for AGSL in that discussion.
Or if we limit discussion to only AGSL definitions, of course they are the authority.
But that's a very limited discussion as we have eliminated the vast majority of all stones available. Many of which will be considered the equivalent to "ideal" cut in terms of quality of cut by many knowledgeable observers
We only have to look at the AGSL Princess Cut grade to see dispel the notion AGSL is the ultimate cut authority. The AGS stones are consistently gorgeous- but there's plenty of other models which are equally well cut- and many would say more beautiful. I believe this is the reason the grade has never been widely embraced.
If one wants a diamond that looks exactly like the next one, and the look they want is the type of optics AGSL grades promote, then the consistently and control you speak of is a necessity.
However I'll never buy the notion that stones are somehow "better" cut simply because they fit a mold.

Getting back to fire, there's surely non ideal cut stones with more potential for fire than another given ideal cut stones

 

[Texas Leaguer]

Here are a couple of pics that show a variety of colored flashes. Some are reflections and some are actual dispersion.



I am always especially intrigued by looking at the fire projected onto the surface beneath the diamond. You can see various saturation levels (some pastels). The individual colors really pop against the dark background. I think that is also an illustration of why you need the proper contrast in the stone to exhibit fire.






Let's call this my attempt to decorate this thread with festive lights. Happy Holidays Everyone !

 

[MelisendeDiamonds]

We attribute AGSL's "Ideal" term here because they are the authority on cut at the moment....

They have some done some interesting research on fire but the last time I saw anything was in 2010.

I would say Peter Yantzer director of AGSL is an authority on Fire, but they don't really consider it a major part of their cut grading.
Sure it may weed out very shallow crown diamonds from getting their top grade as a result of the dispersion metric but they can't really differentiate cuts especially Fancy shapes on the basis of fire.

 

[MelisendeDiamonds]

Rhino, did you say something?

Hope you can contribute to this thread about what causes us to see pastels.
I really think it is unrelated to cut.
Rather, it is a function of lighting in the environment.

Seems plausible, pastels are washed out colors. Mix stronger colored light from narrow point sources with diffuse white light and I'd expect more pastels than saturated colors.

 

[diagem]

thanks Jon- since this an objective discussion, can we use the term "Ideal Optics as defined by AGSL".
It's a proprietary term- like a brand name, as opposed to some sort of scientific description.

Can we agree that other stones, not termed "Ideal" by AGSL will also exhibit fire- In fact, some large faceted shallow diamonds- clearly not termed "ideal" by AGSL may exhibit MORE fire if the facet placement, size and lighting sources are aligned.

I love AGSL Ideal stones- but I do think there's times that aspects attributed "Ideal" optics, as defined by AGSL are overstated.

David, AGSL is named here due to their system identified with the term "Ideal"
Do other cuts exhibit fire (e.g. Small,medium,large,X-Large etc..)? Sure they do, and they are potentially beautiful as well.

But...,

We are not talking "specifically" rounds are we...

When we cut to Ideal optics, we are able to control the sizes of the VF we design so we can control fire effect...

In random generic cuts, no matter how beautiful, the fire and other optical properties are not controlled as designed cuts are...

We attribute AGSL's "Ideal" term here because they are the authority on cut at the moment....

Hi Yoram!
We do see a few aspects differently- and it's a subject we never tire of discussing.
Putting everything else aside- I strongly disagree with the part in bold.
The thread is about fire- no mention of fire in AGSL graded stones i the title.
If we are comparing GIA and AGSL, we'd have a discussion about which lab has more authority- and I can see a very good case for AGSL in that discussion.
Or if we limit discussion to only AGSL definitions, of course they are the authority.
But that's a very limited discussion as we have eliminated the vast majority of all stones available. Many of which will be considered the equivalent to "ideal" cut in terms of quality of cut by many knowledgeable observers
We only have to look at the AGSL Princess Cut grade to see dispel the notion AGSL is the ultimate cut authority. The AGS stones are consistently gorgeous- but there's plenty of other models which are equally well cut- and many would say more beautiful. I believe this is the reason the grade has never been widely embraced.
If one wants a diamond that looks exactly like the next one, and the look they want is the type of optics AGSL grades promote, then the consistently and control you speak of is a necessity.
However I'll never buy the notion that stones are somehow "better" cut simply because they fit a mold.

Getting back to fire, there's surely non ideal cut stones with more potential for fire than another given ideal cut stones

Try to stay on focus, you are swaying and loosing the point of this thread..., or it's title...

We are speaking of facet size, VF size and the way they display the colors of the spectrum as flashes of colorful fire.
This directly relates to the design and the ability to complement crown and pavilion facets in such a manner which has the potential to display unobscured pavilion facets thus enabling controlled flash size and on-off events.
The more precise the cut within its design the more control in the sizes and speed of the fire flashes.

Not talking about "beauty or better" etc, it won't help steering it in that direction.
Generics cuts have random fire flashes vs. designed cuts which can potentially have planned flashes.

And yes, what can you do, currently AGSL holds the title to "cut grading" authority...., unfortunately they are limiting innovation but they are in their respected position the authority!! So when we want to talk optical symmetry and it's advantages we talk the "Ideal" language, it's simply more scientific.

Nothing to do with beauty of more/less or better...

 

[Rhino]

Greetings Harout,

A pleasure to make your acquaintance.

a. ideal optics
c. since diamonds with ideal optics are the best at capturing and reflecting back the surrounding environment you are also seeing reflections of colors within that environment

'Ideal optics" in a round brilliant at least what is marketed on Pricescope as "Ideal H&A" as ideal is not optimized for fire not even close. 34.5/40.8/77 A "Tolk Ideal" is balanced with good brightness and fire, brightness is favoured over fire.

Good point. GIA favors brightness over fire as well however this is for good reason as people observe brightness exponentially more than they do fire. Shallow angled combinations (which also score low on the HCA) can have great fire but the bit more fire at the expense of the brightness it sacrifices is, IMPO not worth it. UNLESS of course a person is in spot lighting conditions considerably more than they are diffuse.

Other combinations can produce more fire at the expense of brightness.

Most fire from Round Brilliant is seen in the arrows, it is caused by clipping not by dispersion.
Part of white light is "clipped" making the arrows colored.

Larger VFs allow more chance for clipping and greater seperation of colors allowing the observance of more fire.

Amen.

Peace,
Jon

 

[Serg]

Saturation of colour flashes depends from:
1) Light source Angular size
http://www.gemology.ru/cut/english/grading1/index.htm
2) pupil angular size ( depends from distance between observer and diamond, and surrounding brightness )
for more detail check http://www.gemology.ru/cut/english/rainbow/3.htm and next page
3) Cut geometry
4) position light source relative to ETAS spot from human pupil

and many other things

 

[Garry H (Cut Nut)]

Rhino, did you say something?

Hope you can contribute to this thread about what causes us to see pastels.
I really think it is unrelated to cut.
Rather, it is a function of lighting in the environment.

Seems plausible, pastels are washed out colors. Mix stronger colored light from narrow point sources with diffuse white light and I'd expect more pastels than saturated colors.

I do not see pastel colors in diamonds.
I see rainbow colors.

Colors are made up of 3 variables.
Hue – Imagine around the ‘equator’ - all fire is part of the most saturate hues from the rainbow.
Tone – lightness or darkness
Saturation - The intensity or saturation of color

I suppose it is possible that one eye can see bright or dark from a facet, where the other eye sees a rainbow hue with strong saturation, and this can get mixed up in our mind.
But the ordinary single lens photo's can not show that - they show rainbow colors.

 

[diagem]

Here are some images I took of an OMC attempting to bring out pastel colors.
With slight & slow tilting I was able to bring out some pastel colors.
We can clearly see the bleeding of the blue into a pastel blue hue...
Its easier when you attempt this on a rather large unobstructed facet like this OMC has.

 

[lknvrb4]

I noticed with my cushion brilliant that the pastels usually show up in the NSWE position only, weird.

 

[WinkHPD]

Who defines "Ideal Optics"?

AGS

This!

 

[Rockdiamond]

Try to stay on focus, you are swaying and loosing the point of this thread..., or it's title...

We are speaking of facet size, VF size and the way they display the colors of the spectrum as flashes of colorful fire.
This directly relates to the design and the ability to complement crown and pavilion facets in such a manner which has the potential to display unobscured pavilion facets thus enabling controlled flash size and on-off events.
The more precise the cut within its design the more control in the sizes and speed of the fire flashes.

Not talking about "beauty or better" etc, it won't help steering it in that direction.
Generics cuts have random fire flashes vs. designed cuts which can potentially have planned flashes.

And yes, what can you do, currently AGSL holds the title to "cut grading" authority...., unfortunately they are limiting innovation but they are in their respected position the authority!! So when we want to talk optical symmetry and it's advantages we talk the "Ideal" language, it's simply more scientific.

Nothing to do with beauty of more/less or better...

Yoram- to your point about AGSL cut grading being "scientific":
Taken in context with your statements about the science behind optical symmetry, precision in cutting and unobscured pavilion facets, the term makes perfect sense.
But AGSL cut grading is not "more scientific" than GIA cut grading. It may be more precisely calibrated in result- but there's no doubt GIA possess far grater resources for scientific testing than AGSL. If GIA wanted to narrow the EX cut grade to an even more finite window than AGSL, they certainly have the technology to do so.
The point is that the cut grades of both labs are subjective
This is not to imply there's anything "wrong" with AGSL Ideal cut grading. AGSL studies, and cut grading are a tremendous asset to our industry.
But it can't cure the common cold. And ideal optics, while they may produce lovely fire- are not the best recipe for "fire"

Sorry for the threadjack, but I did not bring ideal optics into the discussion- or beauty.

 

[MelisendeDiamonds]

But AGSL cut grading is not "more scientific" than GIA cut grading. It may be more precisely calibrated in result- but there's no doubt GIA possess far grater resources for scientific testing than AGSL. If GIA wanted to narrow the EX cut grade to an even more finite window than AGSL, they certainly have the technology to do so.

What technology would that be? Proof? Article References?

 

[Karl_K]

Who defines "Ideal Optics"?

AGS

This!

which is why the term has become useless.
The AGS concept of ideal is very narrow and based on their assumptions of diamond performance and lighting environment which do not always stand up in the real world.
For example the very topic of this thread it would be very easy for a diamond to get "ideal" and have subpar fire.

 

[diagem]

Try to stay on focus, you are swaying and loosing the point of this thread..., or it's title...

We are speaking of facet size, VF size and the way they display the colors of the spectrum as flashes of colorful fire.
This directly relates to the design and the ability to complement crown and pavilion facets in such a manner which has the potential to display unobscured pavilion facets thus enabling controlled flash size and on-off events.
The more precise the cut within its design the more control in the sizes and speed of the fire flashes.

Not talking about "beauty or better" etc, it won't help steering it in that direction.
Generics cuts have random fire flashes vs. designed cuts which can potentially have planned flashes.

And yes, what can you do, currently AGSL holds the title to "cut grading" authority...., unfortunately they are limiting innovation but they are in their respected position the authority!! So when we want to talk optical symmetry and it's advantages we talk the "Ideal" language, it's simply more scientific.

Nothing to do with beauty of more/less or better...

Yoram- to your point about AGSL cut grading being "scientific":
Taken in context with your statements about the science behind optical symmetry, precision in cutting and unobscured pavilion facets, the term makes perfect sense.
But AGSL cut grading is not "more scientific" than GIA cut grading. It may be more precisely calibrated in result- but there's no doubt GIA possess far grater resources for scientific testing than AGSL. If GIA wanted to narrow the EX cut grade to an even more finite window than AGSL, they certainly have the technology to do so.
The point is that the cut grades of both labs are subjective
This is not to imply there's anything "wrong" with AGSL Ideal cut grading. AGSL studies, and cut grading are a tremendous asset to our industry.
But it can't cure the common cold. And ideal optics, while they may produce lovely fire- are not the best recipe for "fire"

Sorry for the threadjack, but I did not bring ideal optics into the discussion- or beauty.

You keep mentioning best..., the difference is I don't!

 

[diagem]

....In fact, some large faceted shallow diamonds- clearly not termed "ideal" by AGSL may exhibit MORE fire if the facet placement, size and lighting sources are aligned...

I will answer you with your own words on this one....

Who and what determines how accurately and precisely these facet placements [and] size are aligned and then some...?
Actually you are right..., it doesn't matter but what does matter it the precision..., the more precise the more control we have as cutters to decide if we want the Diamond to display small/fast events..., or perhaps medium-large/slow events scattered around small/fast events etc...

As far as I know, AGSL's system force cutters to reach this level of cutting as opposed to GiA's wider top grade allowance.
AGS's system is no saint either, they are stuck in the first decade of the new millennium and are limiting cutters who have reached and conquered their system..., it's not all about rounds and princesses anymore!!!

But you have nailed the subject..., the more aligned the 3D cut of a Diamond the higher the possibilities for us cutters to design new and interesting cuts...

Emphasizing..., not best, better or more beautiful!!!!

 

[Garry H (Cut Nut)]

David Rockdiamond, please do not change the topic.
You surely have a lot to offer I am sure.
leave up. Everyone knows your opinion about 'ideal- cut' and blah blah blah.
It does not do it for me either, and AGSL outside some small clicks is pretty irrelevant anyway. So read the topic and give your views, or stop posting here please.

 

[Garry H (Cut Nut)]

I noticed with my cushion brilliant that the pastels usually show up in the NSWE position only, weird.

Are these pastels or pale rainbow hues? If the camera exposure was changed could they become regular fire?
What is the boaundary between what people are calling pastel and regular fire?

is it possible that there is simply a bright reflection off the facet that has some fire showing which reduces the apparent brightness of the fire.

 

[diagem]

I noticed with my cushion brilliant that the pastels usually show up in the NSWE position only, weird.

Are these pastels or pale rainbow hues? If the camera exposure was changed could they become regular fire?
What is the boaundary between what people are calling pastel and regular fire?

is it possible that there is simply a bright reflection off the facet that has some fire showing which reduces the apparent brightness of the fire.

Perhaps slight movements between spectral colors? But there goes the fire logic...

 

[Serg]

I noticed with my cushion brilliant that the pastels usually show up in the NSWE position only, weird.

Try take photos with different apertures. for smaller aperture you have to receive more saturated flashes

 

[MelisendeDiamonds]

I noticed with my cushion brilliant that the pastels usually show up in the NSWE position only, weird.

Try take photos with different apertures. for smaller aperture you have to receive more saturated flashes

This has been presented before.
"Chance of seeing only part of the color fan increases as your pupil becomes smaller"

 

[MelisendeDiamonds]

Simulating the clipping effect by narrowing the camera aperture and moving the camera to get different colors.