AGS 000 and ImaGem results

[RockDoc]

I looked at the First Light Card

This report only shows numbers, but no relationship as to what the numbers mean. I think I''ve seen something that stated the limits of each number rating but it isn''t on the report. No grading as to Excellent to Commercial grade mentioned in this one.


I looked at the Light Performance Report on your site.

I see it reports numbers and it has a "rating" system at the bottom using letters.

Commercial is abbreviated CM. While for us in this discussion, we assume what that means, but would a consumer not familiar with the system.

Also I looked at the sample image which does not show much in the way of optical symmetry, yet it is rated Very Good.

I will grant you I''ve seen attractive stones that do not have the most "aligned" symmetrical patterns, so I find this confusiing as what this is reporting.

My opinion of this is that the report really needs to be more than just the credit card which explains the grading system IMAGEM is using. Constructively my take on this is that it needs a full page style report. Maybe the IMAGEM does that and I haven''t seen it.

Rockdoc

 

[oldminer]

RockDoc;

AGA does make full sized reports using ImaGem with numbers, words, explanations, etc. It seems the best choice for a complex subject, but we wanted to offer a compact product that could serve as a low cost add-on to any other lab report, therefore the smallish plastic card product.

The words and their abbreviations are explained in various places, such as on the back of the small card product. In India, where litigation is far more rare, we have much less in the way of disclaimers and therefore more space to explain.

While you and I probably would prefer numbers AND words, there are many dealers who will prefer only words to explain performance. Since higher performance is not necessarily a descriptor of more beauty, the words do suffice. Diamonds that score Excellent OR Excellent + will all be very lovely stones. Why kill them with a borderline number situation? We agree, and allow people to use the ImaGem information in a way that they prefer to use it.

Labs offering advice and data, like you and I, may well wish to provide the numbers and the word grades. This is how we differ from vendors as independent third parties. Beauty remains subjective, but just like with people''s faces, we all know when a person is not so pretty. Our human perception is a good guide. Meanwhile, engineer types probably like numbers more than words. We want them to be happy in their own little measured worlds, too. They will select diamonds exactly for numerical performance since to them performance is proof of beauty and the more beauty, the better. I don''t agree with that, but each personality type has its own flaws and pluses.

 

[oldminer]

"''ImaGem Diamond Spin"

Please look at the Video Gallery, upper left. See a new video of diamonds in motion from the ImaGem grading device. The first stone is a well cut round diamond, the second stone is a poorly cut CZ and the last stone is a well cut princess cut CZ. These are not photo-real simulations, but real videos, un-retouched.

 

[strmrdr]

Date: 6/16/2006 3:49:39 PM
Author: oldminer
''''ImaGem Diamond Spin''


Please look at the Video Gallery, upper left. See a new video of diamonds in motion from the ImaGem grading device. The first stone is a well cut round diamond, the second stone is a poorly cut CZ and the last stone is a well cut princess cut CZ. These are not photo-real simulations, but real videos, un-retouched.

kewl
in a couple places you can see the glare of the glass its sitting on.

 

[oldminer]

There is also a beam splitting mirror involved and a glass top plate either or both of which may creates a bit of secondary imaging. It can be totally eliminated, but I thought it sort of added interest to the presentation. Marketing of the "look" may be as important as the gemology aspect.

 

[pricescope]

Date: 6/16/2006 3:49:39 PM
Author: oldminer
''''ImaGem Diamond Spin''

Please look at the Video Gallery, upper left. See a new video of diamonds in motion from the ImaGem grading device. The first stone is a well cut round diamond, the second stone is a poorly cut CZ and the last stone is a well cut princess cut CZ. These are not photo-real simulations, but real videos, un-retouched.

embedded player: http://diamondscope.pricescope.com/?src=ImagemDiamondSpin01.wmv
or
stand-alone player: http://diamondscope.pricescope.com/files/ImagemDiamondSpin01.wmv

 

[Rhino]

Hi Dave,

Thanks for the response.

Date: 6/16/2006 2:10:55 PM
Author: oldminer
''As I have been accommodating in explaining to Dr. A what I mean by both direct or diffuse lighting, would he be so kind as to explain what he means when he says direct diffused lighting and perhaps provide an example as I have done? That would be appreciated.''


Direct, non-dffused light is where the light comes from the source and falls directly onto the object. (Gemex)
Direct, diffused is where light passes through a filter or softener screen and falls directly on the object (ImaGem)

Non-Direct light is when light is reflected off of a mirror or a surface, such as an integrating sphere before it contacts the object.
Non-Direct diffused light has a filter or softener screen between the light and the object in addition to its being reflected.
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Ok... I see how you''re breaking it down. One thing that may throw a little confusion into this explanation which you may want to alter slightly is the light reflected off of a mirror part. Becuase light that shines into a mirror and bounces onto an object (like diamond) can be just as intense as the direct light itself. I would assume you''re referring to reflected ambient light though. I''d leave the mirror part out for less confusion.

The definition of Direct, diffused is similar to what I refer to as diffused lighting but as I view your video it is clearly not exactly the same. As I view the video you posted it appears that the lighting is causing the bright flashes typically found in direct lighting environments, yet not strong enough to induce fire. I also see external reflections as well taken into account. I''ll put a video file together of what the BrillianceScope sees when its doing its analysis for a comparison. I greatly appreciate you doing that Dave. It''s a big help in learning how the Imagem does its anlaysis and I can see how it and the Bscope would corellate in their results.

When you seen the lighting ring move down in Gemex it is creating 5 differing angles of lighting. ImaGem simply uses quite the same total angles but makes it happen all at one time with a broad, direct-diffused light source at a distance that allows it to happen. This is a vital difference between the two units in spite of similar outputs. We also believe the use of diffusec light is crucial to being able to measure what needs to be measured in a meaningful way.

xxxxxxxxxxxxxxxxxxx

I understand your comments but at the same time one advantage to the analysis of the Bscope that I see, due to its direct light evaluation, is its ability to see fire and the literal breakdown of the spectral display from bright white flashes to the colors of the spectrum. By diffusing/filtering the direct light the Imagem is muting colored light return and only recording/reading the bright white flashes. There''s nothing wrong with this but it appears, as you have pointed out to be a fundamental difference between the 2 technologies. IMO both give meaningful results because there are environments in which both types of assessment''s can be drawn.

We believe the predictive tools are excellent for cutters to use as a guide, but for jewelers and consumers who want to know with certainty how their one unique diamond performs, then one must measure the performance on that stone versus predicting by measuring parameters.

Totally agree. A real assessment of performance by shining light directly onto the diamond being analyzed is always best IMO too. It''d be nice to know how big the hole in the cone is above the diamond being tested in the Imagem.

Parametric screening works. I have been providing a crude but useful tool for all shapes since the late 1980''s and have had my share of abuse from those who used to say ''Parameters don''t work.''. Now, muich of what we hear is ''Parameters work'', but of course we now measure more parameters with better precision. I have said they work all along, but are not the way to make a finalk judgment when there are better tools Whenever I have a diamond to weigh and have a scel, I put it on the scale. If I don''t have a scale I measure the stone and use a calculator, specific gravity and a formula to ESTIMATE the weight. Anyone knows which is preferred and most accurate.... What I see is a new style of scale that will quickly weight the performance of light with the confidence one gets from a digital scale when one needs a carat weight.

Well ... these are the attempts from the technological companies and there is good science to be found in them. As I''ve stated before I don''t think I''ve found one that I''d call "flawless" but I have to tell ya one thing that I like about the parametric approach, at least with what GIA has done is base their parametric approach on their observation testing and providing the details down to star and lower half length. If they''d have included upper half angles that would have made it more complete imo. With me, parametrics don''t work unless you have all facet set details. Not the basic minimums commonly reported on most Sarin/OGI''s.

Peace,

 

[Rhino]

Date: 6/16/2006 2:39:22 PM
Author: jasontb
Light from a source reflected off a mirror at an object is non-direct? Why? Isn''t it the same as if the light source were pointed directly at the object?

LOL... exactly my thoughts Jason. I requested Dave alter that in his definition to avoid confusion.

 

[oldminer]

Okay, I''ll try to give a better explanation.

1. The mirror is not directing light to the diamond but from the diamond to a camera. ALL the light falling on the diamond in the Verigem is direct lighting. ALL the light used to measure light behavior is direct, diffused lighting. The bright reflections off the crown facets and any glare, flare, etc are from non-diffused lighting that is being employed to create a useful and welcome sort of marketing tool for retailers and sales efforts. In measuring performance of diamonds, we don''t use glaring lights and too much brightness. How can one tell which part of a a diamond perform best, next best , next best, if too much lighting is pumped in and we can''t discriminate performance? Too much light and any diamond would look brilliant. Just the right amount is used to make these measures.

2. In the videos we did use some direct, non-diffused lighting to create some vestiges of fire, lively sparkle and some glare reflection. I think it is an effective sales gimmick, but not how the stone is measured. If we video taped the the measuring routine, it would be quite lifeless by comparison, although more useful for grading.

3. Rhino, I don''t know what you mean about the size of the "hole in the cone above the diamond"?

4. One of the most important efforts of all of this is for gemologists to accept and learn to communicate within the accepted existing norms of scientific language. Terms are very specific and thereby universally understood at great distances. One of our largest failings to date has been to adopt accepted definitions of terminology so that we begin each new lesson on a firm foundation of complete understanding. Even when we don''t agree, we must at the very least, know that our words will be understood in the proper context. I have been taken to school over the use of the following words: Accuracy, Precision, Consistency, Repeatability, Normal Lighting, Standard Deviation, Gray Scale, and several other words and terms to the point where I now use them more carefully . One of the tragedies of modern English is the loss of the nuances of meaning of slightly different words. Communication tends to be short and unclear as vocabulary size decreases. There are languages with a lot more variation in words and their meaning than what we have with modern English. We need to work as much on clear self expression as with the details of science. It really helps when we use the best terms in their most proper sense. This is not directed any anyone. Please don''t feel it is YOU that is being addressed. It is just an observation and a wish.

 

[jasontb]

Dave I think you are missing my point. My point is, you defined direct and diffuse as:

Date: 6/16/2006 2:10:55 PM
Author: oldminer

Direct, non-diffused light is where the light comes from the source and falls directly onto the object. (Gemex)
Direct, diffused is where light passes through a filter or softener screen and falls directly on the object (ImaGem)

Non-Direct light is when light is reflected off of a mirror or a surface, such as an integrating sphere before it contacts the object.
Non-Direct diffused light has a filter or softener screen between the light and the object in addition to its being reflected.

Or in other words: Direct = light --> object
Non-Direct = light ---> mirror --> object

As far as the light and the object are concerned, these scenarios are identical. Sure geometrically one is 'direct' and one is 'indirect', but seeing as how a mirror doesn't change the light, I don't see the point in differentiating between the two.

I guess we are just looking at it differently. In my mind, and I think Rhino's, light is either direct (no filter or screen) or diffuse (filter or screen). The use of a mirror is not an issue. Perhaps I am overlooking something that would make the use of the mirror significant?

 

[strmrdr]

Dave, no the problem is companies trying to change the meaning of words to suit them.

Lets look at some official definitions:

diffused:

Adjective
S: (adj) diffused ((of light rays) subjected to scattering by reflection from a rough surface or transmission through a translucent material) "diffused light"
S: (adj) soft, diffuse, diffused ((of light) transmitted from a broad light source or reflected)


direct:
Adjective
S: (adj) direct (direct in spatial dimensions; proceeding without deviation or interruption; straight and short) "a direct route"; "a direct flight"; "a direct hit"
S: (adj) direct, unmediated (having no intervening persons, agents, conditions) "in direct sunlight"; "in direct contact with the voters"; "direct exposure to the disease"; "a direct link"; "the direct cause of the accident"; "direct vote"
S: (adj) direct (extended senses; direct in means or manner or behavior or language or action) "a direct question"; "a direct response"; "a direct approach"
S: (adj) lineal, direct (in a straight unbroken line of descent from parent to child) "lineal ancestors"; "lineal heirs"; "a direct descendant of the king"; "direct heredity"
S: (adj) direct (moving from west to east on the celestial sphere; or--for planets--around the sun in the same direction as the Earth)
S: (adj) direct (similar in nature or effect or relation to another quantity) "a term is in direct proportion to another term if it increases (or decreases) as the other increases (or decreases)"
S: (adj) direct ((of a current) flowing in one direction only) "direct current"
S: (adj) direct (being an immediate result or consequence) "a direct result of the accident"
S: (adj) direct, verbatim (in precisely the same words used by a writer or speaker) "a direct quotation"; "repeated their dialog verbatim"
S: (adj) direct (lacking compromising or mitigating elements; exact) "the direct opposite"
Adverb
S: (adv) directly, straight, direct (without deviation) "the path leads directly to the lake"; "went direct to the office"

direct diffused light is a contradiction in terms.

 

[researcher]

Date: 6/15/2006 1:51:24 PM
Author: Rhino
Awesome ASET image researcher!

Thanks! I haven''t seen more than 2-3 ASET images of princess cuts and therefore don''t know exactly what a great one looks like, but I figured it had to be fairly good considering how much I love my stone

Date: 6/15/2006 5:34:14 AM

Author: Rhino

I do know the cherry sets though and that''s what''s important to me.

And to the consumers!

In fact, it is these 3d models that AGS generates (I believe they are using the Sarin for this, although they do own a Helium as well) and loads into their own ray trace software which basically generates the grade. This is how they are accurately grading performance and determing the light performance grades.

THANK YOU for making this clear to me. I figured they must use some sort of technology like the Helium scanner, but with all the debates regarding the reliability of various technologies on PS I was curious what they used--and what they measured.

There are certain limitations to reflector based technologies (including ASET) and ray trace software which have been adopted into the AGS system which some view as a weakness because not always do the results corellate to human observation. I would say they do in most circumstances but not all. No system, IMO is flawless.

I do enough performance measurement consulting to understand such standard deviations and not concern myself too much with them

Have an appraiser and/or AGS jeweler with the AGS PGS software run the model to determine AGS light performance score.

You (and others) have software that will tell you the light performance score? This is WONDERFUL!!! If, for instance, I find a GIA graded stone that I feel is a winner you could determine the AGS light performance score? This technology could really help me in choosing earrings as I care more about their performance matching than getting exact color or clarity.

It''s interesting you should ask this because we just recorded footage of this type of comparison comparing various flavors of AGS Ideal princess cuts. One of those comparisons being the difference in chevrons on the pavilion. I wasn''t going to publish this until I finished another project I''m currently working on covering the differences in appearance between GIA Ex vs GIA VG''s but later on when I get up to the store perhaps I can snap off a comparison shot for ya and show you how they look in a static position. Currently, within the realm of AGS Ideal princess cut there are more stones available of the 3/4 chevron type than there is the 2 chevron type. Both are beautiful yet vary in their appearance. The fewer chevrons contribute to a braoder flash look while the 3/4 chevron variety contribute to higher pin flash.

Please do share your findings! I''ve found in my own diamond searches that I prefer stones with more pinfire, so it''s good to know that I should look for stones with more pavilion facets.

Now, does the crown height affect just the amount of fire or does it also impact the type of fire? The reason I ask is my stone exhibits broad flashes along with pinfire when I tilt it at an angle, and I''m just curious if the crown height/facets are responsible in any way for the light performance when viewed at an angle.

Your post makes 100% sense researcher. I hope my answers are worded such that you can easily understand them. If you need clarification on anything don''t be afraid to ask.

I can''t thank you enough for taking the time to respond to me. I realize that most experts probably roll their eyes when a novice like me tries to participate. It means a lot to me that you not only took the time to read my posts but to respond in such a way that I could easily follow. I honestly can''t thank you enough for your consideration

 

[RockDoc]

Hi Reseacrher...


If you have or can get the .srm file or the .stl file, and email to me, I have the PGS software, and I can run the process for you to estimate the AGS cut grade.

The sort of "glitch" here is that it really requires a PERSON to evaluate the symmetry and polish.

If the GIA report says its excellent /excellent for polish and symmetry, I can ASSUME that it can be matched to an AGS rating for it.

It is very new software, and it is not supplied to the trade in general with the cut grading results. The trade version does not approximate the cut grade.

The "problem" here is if the polish and symmetry don''t equate to the AGS Ideal polish and symmetry grade the result will not be accurate, but I can enter in the data using Ideal and 1 or 2 and report the results for you.

As for participation, such as yours, I doubt the experts are rolling their eyes. At least I don''t roll my eyes at the posts you''ve made, if that counts for anything.

Rockdoc

 

[researcher]

Date: 6/16/2006 2:08:33 PM
Author: Rhino
In relation to the topic of this thread and inspired by ''researchers'' questions I thought I''d like to share what footage we have taken so far with regards to various AGS Ideal Princess cuts in the following video file. This video is not yet complete but 2 of the comparisons relate directly to questions researcher has asked with regards to


1. Differing appearances between AGS Ideal Princess cuts.

2. How the amount of chevrons on the pavilion alter the appearance.

3. How even stones with teh same amount of chevrons can be impacted by proportion combinations.


http://www.goodoldgold.com/videos/AGSIDEALPRINCESS.wmv


In this short clip the following comparisons are made.


1. The first comparison is of 2 Princess cuts that we have found differs in light performance yet both get the AGS Ideal grade for ''light performance''. The stone on the left is a GIA stone we hand selected but on the PGS software gets ideal for light performance. The stone on the right in the first comparison is an AGS graded Ideal. Both of these stones have the same number of chevrons on the pavilion (4 chevrons plus the mains), both have Ideal polish & symmetry. Here the BrillianceScope results concur with the eyes and since I''ve found corellations between Bscope and Imagem I would suspect would also rank accordingly on the Imagem as well. I''m pretty confident about that. In this post and the next are the Bscope results of each. In this post is the results of the stone on the left. Next post will be the stone on the right.


2. In the 2nd comparison we''re examining a 4 chevron princess alongside a 2 chevrong princess. Both ideal light performance yet differ in appearance.


Hope you enjoy this researcher and anyone else following along here. I am finishing another project but when that''s done plan on finishing up the completion of this princess comparisons of AGS ideals (for light performance).


Kind regards,

You''re the best!!! I LOVE this comparison video! It really shows EXACTLY what I have been wanting to know. This should be one of the first things shown to consumers looking at princess cuts. It''s SOOOOO helpful!

And, as an owner of a GIA stone, I love that fact that this GIA holds its own with the AGS graded stone!

I do have one question though that ties into my previous post. While I now know I tend to prefer stones with more chevrons on the pavilion (I''m all about the pinflashes), there is something that still affects the amount of brilliance and fire I see in these stones. I noticed with the stones in the first example that the GIA stone seems to have a smaller table (my guess is around 66%) while the AGS stone has a larger (possibly 74%) table. Is there a difference in the crown height as well? The reason I ask is I''m curious if there''s a trend with the overall look of the performance of the stone based on the crown and/or table when paired with a 3/4 chevron pavilion. I''m not trying to determine the "best" proportion combinations, but as a consumer I''m wondering how the various combinations affect the play of light in general. I mean, in comparing the ASETs of the two stones would the GIA stone have more red and blues and the AGS more green? While I do think both stones are extremely nice, my preference is definitely for the GIA graded stone and I''m therefore wondering if there are basic parameters I could look for to achieve a similar appearance.

Rhino, THANK YOU for making this video. It really makes the differences in appearance of AGS stones apparent and stresses the importance of working with a vendor who''s knowledgeable about this visual differences and has an eye for choosing the best of the best stones.

 

[researcher]

Date: 6/18/2006 4:46:30 AM
Author: RockDoc
Hi Reseacrher...



If you have or can get the .srm file or the .stl file, and email to me, I have the PGS software, and I can run the process for you to estimate the AGS cut grade.


The sort of 'glitch' here is that it really requires a PERSON to evaluate the symmetry and polish.


If the GIA report says its excellent /excellent for polish and symmetry, I can ASSUME that it can be matched to an AGS rating for it.


It is very new software, and it is not supplied to the trade in general with the cut grading results. The trade version does not approximate the cut grade.


The 'problem' here is if the polish and symmetry don't equate to the AGS Ideal polish and symmetry grade the result will not be accurate, but I can enter in the data using Ideal and 1 or 2 and report the results for you.


As for participation, such as yours, I doubt the experts are rolling their eyes. At least I don't roll my eyes at the posts you've made, if that counts for anything.


Rockdoc

You are too kind.

I'm actually just browsing for stones right now, but I will definitely take you up on your offer when it's time to choose the stones for my earrings

I do have a .srn file for my e-ring stone, but it scored only VG for both symmetry and polish. My local appraiser thinks it should be GIA EX for symmetry, but either way it wouldn't be AGS ideal for either

Now that there are more stones on the market I should be able to find some fantastic ones for earrings, and I will send them to you for appraisal (the local appraisers I've gone to (3 of them) aren't exactly knowledgeable when it comes to princess cuts)).

Thanks again for participating in this thread! It's my favorite in all the time I've been a member of PS!

 

[RockDoc]

Rhino

1. The first comparison is of 2 Princess cuts that we have found differs in light performance yet both get the AGS Ideal grade for ''light performance''. The stone on the left is a GIA stone we hand selected but on the PGS software gets ideal for light performance. The stone on the right in the first comparison is an AGS graded Ideal. Both of these stones have the same number of chevrons on the pavilion (4 chevrons plus the mains), both have Ideal polish & symmetry. Here the BrillianceScope results concur with the eyes and since I''ve found corellations between Bscope and Imagem I would suspect would also rank accordingly on the Imagem as well. I''m pretty confident about that. In this post and the next are the Bscope results of each. In this post is the results of the stone on the left. Next post will be the stone on the right.


Rhino

Do you have the PGS software? or is this a stone I ran the software based on your scan?

Rockdoc

 

[oldminer]

Date: 6/17/2006 8:02:36 PM
Author: jasontb

Dave I think you are missing my point. My point is, you defined direct and diffuse as:

Date: 6/16/2006 2:10:55 PM
Author: oldminer

Direct, non-diffused light is where the light comes from the source and falls directly onto the object. (Gemex)
Direct, diffused is where light passes through a filter or softener screen and falls directly on the object (ImaGem)



Non-Direct light is when light is reflected off of a mirror or a surface, such as an integrating sphere before it contacts the object.
Non-Direct diffused light has a filter or softener screen between the light and the object in addition to its being reflected.

Or in other words: Direct = light --> object
Non-Direct = light ---> mirror --> object

As far as the light and the object are concerned, these scenarios are identical. Sure geometrically one is 'direct' and one is 'indirect', but seeing as how a mirror doesn't change the light, I don't see the point in differentiating between the two.

I guess we are just looking at it differently. In my mind, and I think Rhino's, light is either direct (no filter or screen) or diffuse (filter or screen). The use of a mirror is not an issue. Perhaps I am overlooking something that would make the use of the mirror significant?

The light is NOT passing through a mirror on the way to the diamond. It is directly hitting the diamond, not passing through any mirror. Some of the light is diffused by a softening filter in the videos I made.

Light can be direct or non-direct, diffused or non-diffused. 4 different conditions are possible. ImaGem uses diffused direct light in all conditions EXCEPT for the videos where a little direct, non-diffused light was used. I hope this clears up the understanding.

 

[Rhino]

Good morning all.

Hi researcher,

I am glad my answers helped you. I''d like to answer the other questions you put forth in your response. Please forgive my delay in responding. We spend a wonderful father''s day at the Bronx zoo.

Date: 6/18/2006 4:00:01 AM
Author: researcher

Have an appraiser and/or AGS jeweler with the AGS PGS software run the model to determine AGS light performance score.

You (and others) have software that will tell you the light performance score? This is WONDERFUL!!! If, for instance, I find a GIA graded stone that I feel is a winner you could determine the AGS light performance score? This technology could really help me in choosing earrings as I care more about their performance matching than getting exact color or clarity.

Within the ways of determining AGS Light Performance Scores the most accurate (outside of sending it to AGS) is to run an accurately scanned model through the PGS software. At this moment only AGS accredited jewelers or appraisers who have purchased the software and own a scanner with the ability to produce the model can do it. Around these parts RockDoc is the only one I know of who owns the software although I know others who have it too.

I''ve been analyzing ideal princess cuts with the ASET since June of last year (wowza ... a year already!) so I am confident in my own ability to determine light performance in princess cuts without the PGS software. The other technologies we employ in our purchasing decisions really help make it all a no brainer for us as well.

Date: 6/18/2006 4:00:01 AM
Author: researcher

It''s interesting you should ask this because we just recorded footage of this type of comparison comparing various flavors of AGS Ideal princess cuts. One of those comparisons being the difference in chevrons on the pavilion. I wasn''t going to publish this until I finished another project I''m currently working on covering the differences in appearance between GIA Ex vs GIA VG''s but later on when I get up to the store perhaps I can snap off a comparison shot for ya and show you how they look in a static position. Currently, within the realm of AGS Ideal princess cut there are more stones available of the 3/4 chevron type than there is the 2 chevron type. Both are beautiful yet vary in their appearance. The fewer chevrons contribute to a braoder flash look while the 3/4 chevron variety contribute to higher pin flash.

Please do share your findings! I''ve found in my own diamond searches that I prefer stones with more pinfire, so it''s good to know that I should look for stones with more pavilion facets.

Now, does the crown height affect just the amount of fire or does it also impact the type of fire? The reason I ask is my stone exhibits broad flashes along with pinfire when I tilt it at an angle, and I''m just curious if the crown height/facets are responsible in any way for the light performance when viewed at an angle.

In case you haven''t read further down this thread I did share the footage I have captured so far regarding 3 flavors of AGS Ideal Princess cuts. I posted this especially for you.

And yes ... if you LOVE the pinfire found in princess cuts with super light performance then you should seek out princess cuts with at the very least 3 chevrons on the pavilion.

Crown height (generally dictated by crown angles) are very important but the difference between broadfire and pinfire flashes are primarily due to the way the mirrors are constructed on the pavilion. When you add more chevron facets to the pavilion you create more smaller mirrors as opposed to wider/broader ones. The presence of more smaller mirrors on the pavilion result in a display of awesome pinflash when combined with the magical proportion combos.

Both flavors are beautiful though.

Date: 6/18/2006 4:00:01 AM
Author: researcher

Your post makes 100% sense researcher. I hope my answers are worded such that you can easily understand them. If you need clarification on anything don''t be afraid to ask.

I can''t thank you enough for taking the time to respond to me. I realize that most experts probably roll their eyes when a novice like me tries to participate. It means a lot to me that you not only took the time to read my posts but to respond in such a way that I could easily follow. I honestly can''t thank you enough for your consideration

The pleasure is mine. Hope you saw and enjoyed the video file!

Kind regards,

 

[Rhino]

heh... I should have read further down the thread.

Date: 6/18/2006 4:58:21 AM
Author: researcher

You're the best!!! I LOVE this comparison video! It really sho

ws EXACTLY what I have been wanting to know. This should be one of the first things shown to consumers looking at princess cuts. It's SOOOOO helpful! And, as an owner of a GIA stone, I love that fact that this GIA holds its own with the AGS graded stone!

Awesome!

My feelings are the same researcher and I am ecstatic that you love em! I've had this video stuff on the backburner for way too long. It's something we've been wanting to do now for years and it is finally coming to fruition. Alot more to come which we'll eventually compile onto a DVD to help folks gain a better understanding of the things going on in the world of gemology which we often discuss here.

The AGS system helped tremendously insofar as finding stones with top light performance but even after a year now the companies that are cutting with AGS light performance are still in the greater minority. In fact I can count them on one hand. The greater majority of princess cuts are indeed accompanied with GIA & EGL Reports and we still call those in as well but finding the cherries are of course more challenging amongst the GIA stones since there is no grading of light performance on the GIA report.

Date: 6/18/2006 4:58:21 AM
Author: researcher

I do have one question though that ties into my previous post. While I now know I tend to prefer stones with more chevrons on the pavilion (I'm all about the pinflashes), there is something that still affects the amount of brilliance and fire I see in these stones. I noticed with the stones in the first example that the GIA stone seems to have a smaller table (my guess is around 66%) while the AGS stone has a larger (possibly 74%) table. Is there a difference in the crown height as well? The reason I ask is I'm curious if there's a trend with the overall look of the performance of the stone based on the crown and/or table when paired with a 3/4 chevron pavilion. I'm not trying to determine the 'best' proportion combinations, but as a consumer I'm wondering how the various combinations affect the play of light in general. I mean, in comparing the ASETs of the two stones would the GIA stone have more red and blues and the AGS more green? While I do think both stones are extremely nice, my preference is definitely for the GIA graded stone and I'm therefore wondering if there are basic parameters I could look for to achieve a similar appearance.

Here are ASET's and proportions of the first comparison. And I agree ... the GIA stone in that comparison beats the AGS Ideal.

You'll note a higher crown and smaller table on the brighter stone ... just as you speculated.

 

[He Scores]

Someone once showed me data on some princess cuts that were being submitted to Gcal to increase the performance factor.

I took one look at the improved stone data and noticed the bottom corners were corrected to 41 degrees.

Looking at the two stones above, I''d say there is a difference in this piece of important data between the two stones.


Bill Bray
Diamond Cutter

 

[JohnQuixote]

Date: 6/15/2006 4:35:51 AM
Author: researcher

Date: 6/15/2006 1:33:01 AM
Author: JohnQuixote

Researcher, I know you’re an experienced princess enthusiast. Do you feel different angles change the look of yours dramatically? If so, does your single, face-up view still represent the stone''s best qualities to you?

I love how you said ''enthusiast'' as a description for me--I am that!

I''m obviously not an expert, so please bear with me as I massacre the proper diamond terminology! Also, please remember that these are just my personal observations of my stone (I''ve included the virtual ASET as a reference).

Yes, different angles and different lighting does dramatically change the look of my stone. I can''t say for certain what I like best, but I can describe the differences.

When viewed straight on (hand held out straight at eye level in front of me) in bright overhead light I am literally blinded by the reflection off my table and can see lots of pinfire on the crown. When tilted, I get broad flashes of color and white light and my stone seems to reflect the light throughout the entire stone.

When viewed straight on indoors with more diffuse lighting, my stone shows more scintillation than when tilted. However, it appears more brilliant in this lighting when it''s tilted.

In candlelight my stone has lots of pinpoint fire when viewed straight on, and broader flashes of color in addition to the pinpoint fire when tilted just slightly.

Interestingly, the stones in my wedding band tend to look best straight on or with a very slight tilt, but when tilted at say 30 or more degrees I can see dead spots near the corners and the brilliance is not as good

Also, with the stones in my wedding band the fire does not seem to change from pinpoint to broad flashes for the most part. I have to tilt the band just right to catch the broad flashes of light whereas with my e-ring I can move my hand in any direction and get the broad flashes.

Finally, when I use the light that comes with the ideal scope to backlight my rings I think they look best head on, but just slightly (it may be because I like the optical symmetry and contrast in the stones though).

In sum, yes, I do notice differences in the performance of my stone(s) when viewed at different angles, but it''s hard to say if the head on view is best. I can say for certain my stone looks best to me when it''s moving instead of static, but it performs too differently when viewed straight on and tilted to say which is better--especially in different lighting.

I just asked my hubby his opinion and he said he prefers the stone when it''s tilted and we''re in bright light because he likes when I accidentally blind people with the reflection off the table

To each their own!

I''ve been on vacation since last posting in this thread - just returned from the Pacific Northwest today. I''m enjoying this discussion (breaking from digging out from under a week of mail).

Your descriptions make great sense, considering your diamond''s configurations. From memory I recall you have a 70% table or so - that is probably a factor in your husband''s ''blinding'' observation

 

[JohnQuixote]

Date: 6/15/2006 5:34:14 AM
Author: researcher

Now, I have a question. How is it that the cutters decide on the numbers/formula for their princess cuts (and the AGS charts) when, as a consumer, I'm told there's no way to judge a princess cut by the numbers? This question has plagued me from the start. I understand that our inability to go by the numbers is due in part to the limited knowledge we're given regarding the crown and pavilion angles, but that can be remedied by providing those numbers. If that's not enough information and there isn't a perfect tool for evaluating princess cuts, how can AGS accurately grade their performance? What are the employees at AGS being taught about princess cuts and their performance, and why can't we the consumers be given the same information?

I see your questions have been addressed since last week, but I hope you don't mind if I add a few comments.

To understand where we are with Princess cuts we should go back in time, and upstream, to determine how common parameters evolved. The upstream goal at most factories is to produce the most marketable diamond, balanced with saving the most weight. Diamond cutters have recognized attractive configurations in all of the traditional shapes for much longer than Sarin or Helium have been around. This means many diamonds are cut to configurations that have historically proven sellable in common markets, and are appropriate to the rough being cut. Downstream formulas for selecting princess cuts have been adopted previously (Dave’s AGA system is an excellent example), but – as this thread has discussed – you can’t fit fancy shapes into a round hole.

Now, AGS has applied modern science, optics and computer power to develop a diamond-specific ray-tracing engine showing light performance. This has opened some unexplored fancy territory, and caused some head scratching. “It’s the end of the world as we know it” has been Paul’s theme song as he’s worked outside the box to develop some stunning diamonds using new paradigms. Through the process, AGS is returning to the homeland of practical knowledge; handshaking with manufacturers and cutters to verify their findings. Brian met with Peter in Vegas to discuss observations regarding our manufacture and development of 0 princess cuts, from which we are learning a lot!

As with any new system, there will be adjustments over time. There is no doubt that the 0 princess cuts I’ve seen are stunning. Of course I have seen other princess cuts, equally stunning (in my eyes), that did not receive 0. I’ll say the same about AGS grading fancies as I do about GIA finally having a cut grade for rounds: Even if it needs refinement over time, establishing a system is better than having no system. It’s definitely got some iin the upstream world thinking about what they are doing.

The most intriguing thing is that these studies may assist upstream manufacture of fancy shapes that have not been conventionally considered. It could result in some very remarkable diamonds.

Date: 6/15/2006 5:34:14 AM
Author: researcher

Finally, is there a way to at least somewhat predict the light performance of various princess cuts? For instance, does the number of pavilion chevrons impact the brilliance of the stone? Does the number of facets impact the fire such that some stones will exhibit broader flashes while others will exhibit more pinfire in most lighting conditions? It would be extremely useful for consumers to have more information similar to the advice given on PS that, 'as table size increases, the chances of getting a good performer decrease'. Such helpful hints are desperately needed when considering stones on the internet, especially when we're told the tools available don't begin to tell the whole story.

I hope I'm making at least a little sense in this post. Not only is it really late, but my head always spins when these princess cut discussions arise. I can't tell you enough how much I enjoy them though--even when the discussions are way over my head

You’re making complete sense.

And yes, more chevrons on the pavilion, in an overall sense, means more abundant, smaller flashes. Of course, it also depends on table size and crown height… Oh, and the level of symmetry/contrast effects… Oh, and…

 

[JohnQuixote]

Date: 6/18/2006 4:58:21 AM
Author: researcher

I do have one question though that ties into my previous post. While I now know I tend to prefer stones with more chevrons on the pavilion (I'm all about the pinflashes), there is something that still affects the amount of brilliance and fire I see in these stones. I noticed with the stones in the first example that the GIA stone seems to have a smaller table (my guess is around 66%) while the AGS stone has a larger (possibly 74%) table. Is there a difference in the crown height as well? The reason I ask is I'm curious if there's a trend with the overall look of the performance of the stone based on the crown and/or table when paired with a 3/4 chevron pavilion. I'm not trying to determine the 'best' proportion combinations, but as a consumer I'm wondering how the various combinations affect the play of light in general. I mean, in comparing the ASETs of the two stones would the GIA stone have more red and blues and the AGS more green? While I do think both stones are extremely nice, my preference is definitely for the GIA graded stone and I'm therefore wondering if there are basic parameters I could look for to achieve a similar appearance.

Researcher - Did you guess both table % exactly just from viewing the video?

If so, that's amazing.

 

[researcher]

Date: 6/20/2006 8:02:42 PM
Author: JohnQuixote
I see your questions have been addressed since last week, but I hope you don''t mind if I add a few comments.Do I mind? Are you kidding?!?! I feel HONORED to be part of this thread and am grateful for all the feedback I can get!

John, you do have a way with words. Your descriptions are always entertaining and educational--although, as with this post, not always in that order

I have to agree that AGS is making great strides where princess cuts are concerned, but I am not 100% on board yet. I still think there are some great GIA stones out there for people who are willing to search. That being said, I''m sure there are cutters like Brian and Paul who are using the new parameters to cut truly spectacular stones!

I can''t wait to see such stones in person--as long as they don''t make my e-ring seem inferior!

And as for this comment:

And yes, more chevrons on the pavilion, in an overall sense, means more abundant, smaller flashes. Of course, it also depends on table size and crown height… Oh, and the level of symmetry/contrast effects… Oh, and…

 

[researcher]

Date: 6/20/2006 1:48:48 PM
Author: Rhino
My feelings are the same researcher and I am ecstatic that you love em! I''ve had this video stuff on the backburner for way too long. It''s something we''ve been wanting to do now for years and it is finally coming to fruition. Alot more to come which we''ll eventually compile onto a DVD to help folks gain a better understanding of the things going on in the world of gemology which we often discuss here.

A DVD would be FANTASTIC!!! I''d buy one! That visual comparison helped me to understand princess cuts and their nuances. And, it really shows the beauty of well cut princesses!


Here are ASET''s and proportions of the first comparison. And I agree ... the GIA stone in that comparison beats the AGS Ideal. You''ll note a higher crown and smaller table on the brighter stone ... just as you speculated.

I KNEW the one stone had to have a crown less than 10%! I almost said it looked like a 9% crown but then I questioned it because the pavilion is so different than the GIA stone that I thought I might be wrong. How cool is it that I guessed the tables of both stones spot on? It happens all the time when I go to the local jewelers; I can guess the table and crowns within 1-2% with almost 100% accuracy. Maybe that''s a sign that I''m too obsessed!

 

[researcher]

Author: JohnQuixote
Date: 6/18/2006 4:58:21 AM

Researcher - Did you guess both table % exactly just from viewing the video?

If so, that''s amazing.

Yes, I did guess the tables from looking at the videos. As I mentioned in my last post, I think it''s a sign that I''ve spent WAY too much time looking at princess cuts!

 

[JohnQuixote]

Date: 6/20/2006 11:56:26 PM
Author: researcher

John, you do have a way with words. Your descriptions are always entertaining and educational--although, as with this post, not always in that order

I have to agree that AGS is making great strides where princess cuts are concerned, but I am not 100% on board yet. I still think there are some great GIA stones out there for people who are willing to search. That being said, I'm sure there are cutters like Brian and Paul who are using the new parameters to cut truly spectacular stones!

I can't wait to see such stones in person--as long as they don't make my e-ring seem inferior!

Thanks for the gracious comments, Researcher. By the way, I don't think you need to worry about your diamond developing a case of performance envy.

I'd further your statement by noting that just because a diamond was sent to the GIA for grading doesn't mean it would not qualify for 0 light performance under the AGS system. Statistically most would not, but some would. The number of different looks that can receive top marks allows for a variety of tastes. Have you been able to see many 0s next to your own firecracker? I imagine you'd find some with a kindred spirit (side stones, anyone?)

Remember, only a fractional number of princess cuts are being sent to AGS right now, largely by fine-make cutters who have a very educated clientele: It will take time for this pedigree to make the 'rounds.' (pun intended). Speaking of which, consider that round ideal cuts have been around for over 10 years and you still have to search to find them in the mainstream. There are 2 primary reasons for this: (1) Most consumers are still not aware that cut grading exists so demand is limited. (2) Most rounds would not qualify for an ideal cut grade, so why send them to AGS labs when another lab will give the stone better, or no, marks in cut?

This is why I think GIA establishing a cut grade is a positive step on the whole: Consumer awareness about cut will at least be on the radar in conventional situations now, where it has not been before.

 

[JohnQuixote]

AGS has provided cutting guideline charts to manufacturers. Currently they cite 13,510 different ways to cut a princess to receive AGS 0 in light performance. Of course, not all are practical, but it represents the breadth of study. As long as they continue to interface with cutters to understand the theoretical vs. the practical the system will continue to evolve. Check this chart - if you like small, rapid scint look at the crown configuration on the right.

 

[JohnQuixote]

Date: 6/21/2006 12:16:14 AM
Author: researcher

Yes, I did guess the tables from looking at the videos. As I mentioned in my last post, I think it''s a sign that I''ve spent WAY too much time looking at princess cuts!

Wow. Approximating to 65/75 I can see, but to call them out at 66/74, precisely, from a video...

I''ll be watching for you on Jeopardy.

 

[Rhino]

Date: 6/21/2006 12:16:14 AM
Author: researcher

Author: JohnQuixote
Date: 6/18/2006 4:58:21 AM

Researcher - Did you guess both table % exactly just from viewing the video?

If so, that''s amazing.

Yes, I did guess the tables from looking at the videos. As I mentioned in my last post, I think it''s a sign that I''ve spent WAY too much time looking at princess cuts!

Haven''t been able to post in a few days but I also found that amazing researcher!