Does tweaked girdle or edge to edge light return...

[strmrdr]

Under the rules the vendors arent allowed to comment on anothers diamonds so im going to answer the darkness under the table question.

It is caused by the very short LGF% that 8* uses.
Brian doesnt go to that extreme with the new line ACA's which is why you didnt notice it with them. It isnt there.
It has the girdle treatment without the very short LGF% 8* uses which to me makes them better looking diamonds than 8*.
I dont care for 8* because to my eye they look too dark under the table in some situations because of the overly short LGF%.

 

[Rhino]

Hi Mara,

Thanks for your response.

Date: 11/12/2005 5:51:40 PM
Author: Mara
Actually the edge to edge stones didn''t look brighter vs not to me and I didn''t recall seeing darkness under the table. But the above posts re Eightstar and the others may suggest that?

I want to be careful not to point any fingers Mara so let''s try to avoid using brand names. Let''s assume the pix I posted were of unbrandeds. I''m not sure of the rules for you but for me I can not say anything favorably or unfavorably towards any brand and I like that, even if I do want to give my personal opinion regarding a brand.

Keeping this generic however and to address your point ... the darkness seen within the diamond really depends on how much painting was actually done. I find direct corellations to painting and the actual upper girdle angles of a diamond. I address this in more detail our minor facet tutorial but if you think this through logically ... painted/shallow upper half angles are drawing more light from the hemisphere than they are from above. This can also be observed in ASET. Note the attached graphic is of 3 stones that have painted upper halves but to varying degrees with green increasing as you head towards the right. The more that weak light is being drawn from the hemisphere instead of bright light from above, the more this contributes to darkness within the stone. While we do know that painted girdles will take a hit in the new GIA system, at what point it will be determined is not yet known. Slight painting will not take a hit though. Only where it impacts the face up appearance and reduces brightness. I would imagine however that the examples I gave in the pictures above are and would be painted enough to take the hit.

In that image, you posted it DOES appear that the unpainted would appear a bit ''brighter'' from a white light perspective. Do you feel like that is the case in stones you have seen?

As in the examples I posted yes. Generally when I am making visual observations I like to always confirm with another member or 2 of my staff as well. The 2 examples I showed to 4 of my assistants and each of us could see the difference without knowing what the others saw. For the record, the first graphic I posted is identical to the lighting environment GIA used in their observation testing to determine their cut grading system.

For the purpose of this particular discussion it doesn''t matter to me what GIA or AGS considers ideal or not, I just want to know what the experts feel regarding white light return with painted/tweaked vs untouched and how it would look to the naked eye. Non-discernable differences to consumers?

Other experts? I''d like to hear from more than just one person who has seen thousands of stones.

Everyone is welcome to comment of course.

No sweat bout the GIA/AGS position. I just like to note the corellatoins for newbies who may also be reading and want to know where the labs stand on these issues.

All the best,

 

[Rhino]

oops.. forgot the graphic. Looking at this graphic it appears the 2nd and 3rd stones have just about equal painting.

 

[Mara]

Great thanks Rhino and Strm...

This is interesting. So it would almost seem as though between Rhino''s examples and Leila''s examples that the unpainted version with more light leakage would end up looking whiter/brighter/bigger?

Side by side when we viewed a few diamonds at WF...seriously I couldn''t pick out anything, at least not until I closed my mouth and wiped off the drool. I hadn''t thought of this question then but next visit I will have to spend some time trying to see if I can tell a difference with my eyes. Based on the images and Leilas where the diameters of the diamonds are the same average, it seems like the difference is there, but side by side slightly visible which may not necessarily correlate well to ''regular'' viewing...unless you have diamonds side by side on a ring.

 

[Rhino]

Date: 11/12/2005 6:09:45 PM
Author: Garry H (Cut Nut)
Good post Rhino.

Lets see if Leonid can host a video for this demo?

Thanks and good to cya here mate. If we''re gong to pursue video projects there may be more pressing matters folks may want to see in comparisons though this is certainly and already in my plans. We''ll talk more about this in email.

 

[Rhino]

I would also point out that this isn''t always about an either/or thing. A lot of this can boil down to personal preference as some people may indeed prefer the painted girdle appearance. My personal preference is for an unpainted to slightly painted girdle as this does not impact the face up appearance. I prefer the brightness of the unpainted just as you do Mara but we can''t fault folks if they did prefer the painted types. I know you''re not picking on Garry but if he did prefer the painted type that''s all good. Its the $$$ of the consumer who wins and their preference that matters most of course. My advice of course would be to see both and pick what you like best. In stones with painted girdles a positive is that the patterning may be more easily seen in certain other lighting conditions which will appeal to a certain audience.

Peace,

 

[Rhino]

Date: 11/12/2005 8:00:50 PM
Author: Leila
Here is the lightscope of the other diamond.

Thank you for this input Leila. This confirms what we're talking about here precisely as well. From the images you posted you can note the differences in around the upper girdle region. Thank you for this. I'd be curious to know what the upper half angles are on that stone.

 

[Rhino]

Date: 11/12/2005 9:43:48 PM
Author: Leila

Date: 11/12/2005 8:09:50 PM
Author: Garry H (Cut Nut)

Date: 11/12/2005 7:58:04 PM
Author: Leila
I just want to add my experience. I have a pair of diamond studs. One diamond always seems to be a tad brighter and bigger than the other despite both having the same diameter. This is only noticeable when comparing them side by side. And it is obvious to my eye. This is the lightscope of the brighter, bigger looking diamond.

Yes Leile - side by side photo''s - you probably need to do quite a few - and some with normal dirt and some with just cleaned and dry - that would be great.

Even better still - if you can video them?

Are they the exact same diameter?

You''re joking right?

Actually, I''ve tried taking pictures to capture the difference between them but it''s really tough. I don''t think any of the pictures are any good. And I took A LOT. The diamonds are either slightly tilted a certain way different from one another, maybe it''s the way I''m holding the diamonds or camera. But just for fun, I''ll post a couple anyway.

The diameters are 5.01-5.06 and 5.02-5.05.

Not a bad shot Leila.

Garry ...

... taking the shots are easier said than done. Having both diamonds angled in the same manner, holding the camera steady, having the right settings, lighting and keeping it all in focus can be a challenge.

 

[Mara]

Rhino I am definitely not picking on anyone here, that's kind of an odd terminology. I just wanted to know what people really thought. Mostly experts. Since they see so many stones on a daily basis. I know that Garry wants us to think outside of the box and not just be TIC lovers...preferences ARE what come into play with purchases. In a way this discussion is somewhat elitist as it is only considering 'super ideals' or 'ideals' that show that ecxeptional IS image. However, many people do prefer those cuts, and I just am trying to get all the information on the table for people to look it over and yes, make their own decisions.

Regarding painted vs unpainted. My stone now from WF is a painted ES that probably was meant to be ACA. Let me just reiterate once again that it's one of the most beautiful stones I have ever seen and it's better looking than my old 1.29 H SI for whatever reason...it just pops more. Almost the same numbers. John Q said it was probably the bottom girdle facets?

Anyway I would hands down buy a painted girdle stone again, but I have never owned an unpainted that is ideal cut. The ones we saw at WF were stunning with a bit of extra scintillation. So it'd be curious to check that out as well. Especially if there is a possibility it MAY look bigger and whiter especially if I stick with a larger J for my next upgrade.

I have gotten a few PM's from people who saw this thread and were like, what is a painted and unpainted girdle, and found this topic very interesting, and so I think that this thread and this type of education kept on a consumer level is very helpful to people who are just starting out and may be wondering what the slight differences are between 'ideals' out there. Branding can be confusing at times, I think that many times we need to keep things on a consumer level!

 

[Rhino]

Date: 11/12/2005 9:46:47 PM
Author: Mara
I thought it would be fun next upgrade to get a more classic looking stone rather than the tweaked ones which is what I have had up until this point, but at the mercy of inventory and my own impatience...!! The one thing I did notice when comparing stones side by side (without thinking about asking or comparing tweaked vs not...!) is that the classic type edge leakage stones have more visible scintillation. Both were really beautiful obviously, but that was what my naked eye noticed.

Let me make this note Mara which Mike Cowing had also emphasized in the past. The tiny bit of leakage that exists in classic girdles is so infintesimal that it is not notable to the naked eye. It''s too small. Only excessive leakage is notable to the eye as in the "ring of death" seen in steep/deep combos.

I know this may sound counter to logic ... ie. leakage = a brighter appearance, but when the leakage is so minimal, the eye doesn''t pick this up and interpolate this in a negative manner. Painting and digging on the other hand do impact face up appearance and brightness. Digging would be the opposite of painting.

 

[valeria101]

How come I missed this ??

Jonathan & All, great pictures and discussion... however, these two appear quite different and the least of that consists of some pinpoints in the IS around the girdle. The ASSET seems to do a much better job describing the looks (shape of internal reflections?) in the picture.

The ''painted'' one seems to have a less busy look (which makes sense, since two by two facets end up less angled catching light together).

Is this something obvious enough that someone might actually have strong preference for one kind over the other? Between two diamonds at least half the size of this picture... some difference might be pretty darn obvious. But how often does that happen!

 

[Rhino]

Date: 11/13/2005 2:08:36 PM
Author: Mara
Rhino I am definitely not picking on anyone here, that''s kind of an odd terminology. I just wanted to know what people really thought. Mostly experts. Since they see so many stones on a daily basis. I know that Garry wants us to think outside of the box and not just be TIC lovers...preferences ARE what come into play with purchases. In a way this discussion is somewhat elitist as it is only considering ''super ideals'' or ''ideals'' that show that ecxeptional IS image. However, many people do prefer those cuts, and I just am trying to get all the information on the table for people to look it over and yes, make their own decisions.

Haha... I know you''re not picking on him. I was just using Garry''s terminology. Amen to Garry wanting people to think outside the box!!! Also, this discussion doens''t necessarily petain to elitist types of stones Mara... ie. super ideals. There are tons of stones on the market that aren''t even ideal that have these painted and dug out girdles. This conversation actually applies to *all diamonds* and is not just limited to super ideals. Matter of fact it would probably apply less to super ideals and more towards regular ideals and standard type rounds. Factories looking to save weight in their cutting (which constitutes many) incorporate some of these techniques.

I have gotten a few PM''s from people who saw this thread and were like, what is a painted and unpainted girdle, and found this topic very interesting, and so I think that this thread and this type of education kept on a consumer level is very helpful to people who are just starting out and may be wondering what the slight differences are between ''ideals'' out there. Branding can be confusing at times, I think that many times we need to keep things on a consumer level!

I''ll drink to that! If any of my language is going over anyone''s head, please don''t hesitate to ask for clarification. In the near future you''ll see published an entire article on the subject including digging and side by side comparisons under GIA approved lighting conditions as well as what features to look out for in ASET images that indicate these features. I am happy to share my research & studies with whoever is interested in learning.

Regards,

 

[belle]

Date: 11/13/2005 2:06:31 PM
Author: Rhino

You're joking right?

Actually, I've tried taking pictures to capture the difference between them but it's really tough. I don't think any of the pictures are any good. And I took A LOT. The diamonds are either slightly tilted a certain way different from one another, maybe it's the way I'm holding the diamonds or camera. But just for fun, I'll post a couple anyway.

The diameters are 5.01-5.06 and 5.02-5.05.

Not a bad shot Leila.

Garry ...

... taking the shots are easier said than done. Having both diamonds angled in the same manner, holding the camera steady, having the right settings, lighting and keeping it all in focus can be a challenge.

i totally agree with this. i appreciate the efforts here but i think this is an area where diamcalc would be quite useful, if indeed you are interested in the effects of a painted girdle. having all of external factors controlled (exact same angles and lighting etc.) would make for a more scientific comparison. i also think it would be helpful if the two stones were modeled the exact same with only one having a painted girdle. again, if you only want to see the effects a painted girdle can have.
i think strm answered your question best about the color in his post here:

Date: 11/12/2005 8:09:17 AM
Author: strmrdr
Lets back track and consider a few things.


1> diamond color is graded by the color of the material itself, J colored diamond is J colored diamond no matter how well its cut, why?
Because color is graded from the bottom against a white background under specific lighting.

2> face up or apparent color is influenced by cut depending on the lighting conditions

3> Fire and white light return mask color which is why well cut stones look whiter because you are seeing the light return and not the diamond material iself.

4> under lighting conditions where you can see the diamond material itself not masked by returned light the graded color will be more apparent.

Number 4 is where well cut diamonds come into play, they return light over a wider range of lighting conditions therefore they mask the color more often than a lesser cut stone.

As too does the 'new line' mask color more often than the 'classic' line
the only way to tell for sure would be to line up a bunch of each the same color and view them in a wide range of light conditions.

My guess is that they would be pretty close to even overall but thats just a guess.
Both lines are very well cut diamonds and will be returning light under a wide range of conditions.
There may be some light conditions where one cutting style returns slightly more light masking color better but there is likely another where its reversed.

tweaked..painted..not painted..over hill and over dale, your answer is in lighting conditions.

 

[Rhino]

Date: 11/13/2005 2:33:54 PM
Author: valeria101
How come I missed this ??

Jonathan & All, great pictures and discussion... however, these two appear quite different and the least of that consists of some pinpoints in the IS around the girdle. The ASSET seems to do a much better job describing the looks (shape of internal reflections?) in the picture.

The ''painted'' one seems to have a less busy look (which makes sense, since two by two facets end up less angled catching light together).

Is this something obvious enough that someone might actually have strong preference for one kind over the other? Between two diamonds at least half the size of this picture... some difference might be pretty darn obvious. But how often does that happen!

Hi Ana!

Now ... how could you miss this?

We have sent out this exact comparison to many folks over the course of the years so I do have some idea of the statistical results.

The greater majority picked the unpainted. I''d say over 90%. The more pin flashes would also be accurate and is due not only to this girdle feature but also to lower half (lower girdle) cutting as well. Excellent observation!

 

[Mara]

personally i feel like saying it's all dependent on lighting conditions is a cop out to answering the questions...

i think we have gotten a pretty good explanation and the images are great as well, and i think that in general this thread has been pretty informative. if every answer was 'depends on lighting conditions' we'd never have any interesting discussions. obviously lighting conditions do come into play with any diamond, and i don't think this thread is the end all to be all answering this question but it did present some information that previously many did not know about.

i'm happy.

 

[Rhino]

Thank you for your kind response belle.

Date: 11/13/2005 2:39:59 PM
Author: belle

i totally agree with this. i appreciate the efforts here but i think this is an area where diamcalc would be quite useful, if indeed you are interested in the effects of a painted girdle. having all of external factors controlled (exact same angles and lighting etc.) would make for a more scientific comparison. i also think it would be helpful if the two stones were modeled the exact same with only one having a painted girdle. again, if you only want to see the effects a painted girdle can have.

I''ll 2nd the amen. One problem I have found in DiamCalc though is that I can''t tweak the upper girdles to produce this effect. At this point I can only do it with actual diamonds I''ve scanned that have this feature. If you''d like belle I would share with you some files of stones I''ve scanned in that feature this in case you''re running into the same problems I have.

Regarding the comments on color ...

In case I forgot to mention, the diamond in the ring shot is of a "K". Actually in all the shots I took here they were all "K". In many environments you would NEVER believe it was a K. Excellent point about the lighting conditions as some will emphasize color more than others.

Kind regards,

 

[Rhino]

Mara,

If I'm not mistaken, I think the content of strm's and belle's posts were lighting conditions that emphasize color issues instead of the content of your original intent which was darkness vs brightness.

 

[strmrdr]

Date: 11/13/2005 2:54:53 PM
Author: Mara
personally i feel like saying it''s all dependent on lighting conditions is a cop out to answering the questions...

i think we have gotten a pretty good explanation and the images are great as well, and i think that in general this thread has been pretty informative. if every answer was ''depends on lighting conditions'' we''d never have any interesting discussions. obviously lighting conditions do come into play with any diamond, and i don''t think this thread is the end all to be all answering this question but it did present some information that previously many did not know about.


i''m happy.

Yea we did didnt we.
I knew you knew that the lighting is the largest variable as far as color showing but there are a lot of people reading this that dont. hence going back to the basics.
From there the rest comes into play.

 

[belle]

Date: 11/13/2005 2:54:53 PM
Author: Mara
personally i feel like saying it''s all dependent on lighting conditions is a cop out to answering the questions...

i think we have gotten a pretty good explanation and the images are great as well, and i think that in general this thread has been pretty informative. if every answer was ''depends on lighting conditions'' we''d never have any interesting discussions. obviously lighting conditions do come into play with any diamond, and i don''t think this thread is the end all to be all answering this question but it did present some information that previously many did not know about.

i''m happy.

i''m not saying that the information is not useful, that is why i suggested having the stones modeled in diamcalc...if you are interested in the effects of a painted girdle. it is difficult, as rhino noted above, to have all the factors the same and the planets aligned while you snap a picture of 2 dynamic objects to note any meaningful differences. if the stones are modeled in dc, these external influences are removed and only the appropriate information is analyzed.
your original question was whether or not ''tweaked'' girdles could contribute to i/j/k/l stones looking more ''white'' to the casual viewer and whether you think it is a cop out or not, the answer still remains..it depends on the lighting conditions.

 

[valeria101]

Date: 11/13/2005 2:55:40 PM
Author: Rhino

One problem I have found in DiamCalc though is that I can''t tweak the upper girdles to produce this effect. At this point I can only do it with actual diamonds I''ve scanned that have this feature.

Gem adviser files can be uploaded here

If you ever find time. DC does allow some twist for upper girdle facets - is this something else?

On the side... could it be that OEC are mostly cut this way? It may be that I''ve got a small and biased sample, but I remember painted upper girdle facets on the 20% or so high crowns paired with corresponding twists of the pavilion mains so that the resulting girdle outline ends up knife-edge thin all the was and vaguely waved.

 

[Mara]

sorry bellisima...you know i love you but i dont think that the answer is based ENTIRELY on lighting conditions. sure it''s one component which i can agree with. but i think that two stones in the same lighting conditions like leila''s in the same size side by side still do present some sort of education that can be helpful. considering i don''t have a bunch of super ideal stones that i can just pull out of the vault to check out in person. YET!

 

[valeria101]

Date: 11/13/2005 2:54:53 PM
Author: Mara

if every answer was ''depends on lighting conditions'' we''d never have any interesting discussions.

Yeah...

as a matter of method:

Am I wrong to say that ''lighting conditions'' are not a variable of whatever simulation used to render diamond looks, but an assumption to be made (or avoided) before any discussion may begin?

After all, one can always reverse the problem and ask ''what lighting conditions makes one or another diamond model look great. And I am affraid that problem is also solvable, but just tremendously less interesting unless one wants to build some diamond display or photographic setup.

 

[belle]

Date: 11/13/2005 3:21:59 PM
Author: Mara
sorry bellisima...you know i love you but i dont think that the answer is based ENTIRELY on lighting conditions. sure it''s one component which i can agree with. but i think that two stones in the same lighting conditions like leila''s in the same size side by side still do present some sort of education that can be helpful. considering i don''t have a bunch of super ideal stones that i can just pull out of the vault to check out in person. YET!

agreed. the answer is not ENTIRELY dependent on lighting conditions, but my point is that we can''t make definitive observations on one example (or even two) where the conditions aren''t the same. by the same, i don''t just mean lighting!

 

[Mara]

I entirely agree! No definitive observations please.

 

[Garry H (Cut Nut)]

Rhino - the latest Beta DiamCalc lets you tweak all the facets to what ever is concievable.

But even before then it was possible to do it facet by facet.

Do we need another demo for the FAQ on how to use DiamCalc?

 

[Rhino]

Date: 11/13/2005 7:28:14 PM
Author: Garry H (Cut Nut)
Rhino - the latest Beta DiamCalc lets you tweak all the facets to what ever is concievable.

But even before then it was possible to do it facet by facet.

Do we need another demo for the FAQ on how to use DiamCalc?

Are you talking about the stl route? I forgot about that!

 

[aljdewey]

Date: 11/13/2005 7:28:14 PM
Author: Garry H (Cut Nut)

But even before then it was possible to do it facet by facet.

Do we need another demo for the FAQ on how to use DiamCalc?

 

[Garry H (Cut Nut)]

Date: 11/13/2005 7:53:45 PM
Author: Rhino

Date: 11/13/2005 7:28:14 PM
Author: Garry H (Cut Nut)
Rhino - the latest Beta DiamCalc lets you tweak all the facets to what ever is concievable.

But even before then it was possible to do it facet by facet.

Do we need another demo for the FAQ on how to use DiamCalc?

Are you talking about the stl route? I forgot about that!

1st eg is a normal stone with the changes under advanced tab 2 - indexing / painting by azimuth shift

2nd eg - no indexing / aximuth shift. Facet meet points suffered - but angle loweded by 1 1/2 degrees and facet not cut quite as deep. - this is done 1 facet at a time in '' advanced'' - lower left - only avaliable on imported real stones.

 

[Rhino]

Thanks for the clarifications Garry. It is much appreciated.

 

[Serg]

Rhino,

Please read
http://www.octonus.com/oct/products/3dcalc/standard/diamcalc_2-4.phtml