AGS 000 and ImaGem results

[oldminer]

We have seen a few AGS 000 princess cuts in past months and have found that ImaGem measures their light return and performance over a fairly wide range from as low as "Good" to Excellent+" A range of 5 grades in the system we use. One might choose to have a less disciminating system, but regardless of the system, there is some visible difference in performance of these AGS 000 princess cuts.

First and foremost, all of them looked quite lovely, so the news is not bad. However, as measured performance declines, the stones do appear to look somewhat different. Beauty is the choice of the consumer and dealer. A machine does not dictate what one might judge best for their own taste, but for engineer types performance with higher numbers must be handled. So many Internet shoppers are numbers people, we need to address the issue.

Garry Holloway spoke to me about what may be taking place with ImaGem and its measures on Princess cuts. He tells me that some of these AGS 000 diamonds require tilting to perform their best. In fact, the essence of what he said would indicate to me that they don''t perform as well face up as they do at some degree of tilt. I am simply amazed by this. My personal logic tells me that face-up is of utmost importance in grading diamonds. This is from years of experience, not just a traditional viewpoint. If some AGS 000 princess cuts look better when tilted than they do face-up, then they do deserve a lower resulting cut performance grade....At least that''s what I think is right.

Maybe someone with more experience with the AGS 000 princess cuts will have a differing point of view or different information they wish to share. I''d sure be glad to know why the light return is not judged face-up as the primary grading characteristic. All opinions appreciated.

 

[strmrdr]

Im not 100% sure why but your findings are also in agreement with the b-scope scores for them.
Jon found the same thing.

Whats interesting is that he found a lot of consumers prefered the one with the lower B-scope score.

My take is that maybe a technicaly less bright stone that is well balanced can have eye apeal because there are other factors than brightness that affect how the eye views a diamond.
What he did find is that when rocked back and forth the lower B-scope scored diamond actually looked better than the other diamond to him and consumers picked up on it.

My asscher studies shine some light on this because they are less bright than rounds but when you start moving them they put on a light show that very few rounds will ever come close too.
Combined with kewl patterns and the mile deep look that makes them appealing to a lot of people while if you just look at the various scope results they don''t score that well.

But in the real world well cut examples perform well beyond what their static appearance suggests as do some AGS0 princess cuts.

That is what Garry was getting at I think?

 

[Paul-Antwerp]

True, within the grade of AGS-0 princess-cuts, there are still different levels of light performance. We are going for increased symmetry in these stones, which should bring us in the top of the pops.

Untrue, this difference in appearance should not warrant a difference between ''Good'' and ''Excellent +''.

You probably are facing the same problem which many others (including Brilliancescope) have encountered. Since all cut-studies are based on round brilliants, and since most info on cut is readily available and most advanced in this field, machine design and model-design are based on rounds, and tested on rounds. Now, the resulting machine might work well on rounds, but suddenly, it does not seem to work on other shapes.

Actually, what Garry told you, was different:

In good rounds, the light returning to your eyes originates mainly from a very limited area. That is why a good round has so much red in the ASET-scope. In a princess, the light returning to your eyes comes from a much wider origin, hence more green in the ASET of a princess.

That is why:

- a Brilliancescope is hardly usable on Princess-cuts (if it is even useful on rounds)
- Imagem gives uncomfortable results on Princess-cuts
- the info of an Idealscope is limited on princess-cuts

We ourselves have learned more this last year on cut from studying princess-cuts than we ever could from studying rounds. I welcome others to join us in this field. You will quickly learn the limitations of your current knowledge.

Live long,

 

[strmrdr]

Date: 6/12/2006 11:56:16 AM
Author: Paul-Antwerp

We ourselves have learned more this last year on cut from studying princess-cuts than we ever could from studying rounds. I welcome others to join us in this field. You will quickly learn the limitations of your current knowledge.


Live long,

I wont claim to be close to your level of expertness but I did want to say that I found the same thing while studying Asschers.
Part of it is that the answers to most questions are out there for the asking/reading on rounds but with other shapes you have to figure it out for yourself.
The other part is that the 8 fold symmetry of the round design makes it easier than with other cuts.

 

[Garry H (Cut Nut)]

Hi, from internet cafe before dinner in Arezzo (italy).

Actually Dave my comments were really more about the ASET.

I do not like the idea of a fixed and single ASET view from table up (or down). And the same applies to the Imagem / Brillianscope etc too - to a lessor extent.

At this link http://www.ideal-scope.com/using_fancy.asp I wrote about 2 or 3 years ago - well before ASET was announced - I found that the best way to use ideal-scope with princess is to rotate the stone and look for the dead patches. ASET works much better - it is not easy, but not all that hard to master. I think we might need some good and bad CZ masters to help people get the idea?

So with ASET and a pair of tweezers we can really sort out the best stones.
AGS also use tilted ASET and other images in this way - and it helps to identify stones that you woulod ping because of large ugly leakage zones that look terrible. But still face up the stones should look great.

Bscope and Imagem do focus on the top veiw only - and because we have 2 eyes - we will always have the chance to prefer different stones to these machines - but that should not make a huge difference in 90% of stones.

Hope that helps Dave et al.

 

[firebirdgold]

As far as the tilt question goes and why some people prefer the princesses with the lower scope score, what owner actually looks at their diamond ring straight on? .. ok I''m sure plenty of PSer''s do, but some of them also clean their ring twice a day, travel with an ultrasonic/steam cleaner, and regularly examine their ring(s) with a loupe... not actually normal consumer behavior. (no offense!)

But during the course of the day, and also when the person trys on the ring in a store, she''ll be looking at it with a tilt.

(JMHO)

 

[strmrdr]

Date: 6/12/2006 12:22:54 PM
Author: IndieJones
As far as the tilt question goes and why some people prefer the princesses with the lower scope score, what owner actually looks at their diamond ring straight on? .. ok I''m sure plenty of PSer''s do, but some of them also clean their ring twice a day, travel with an ultrasonic/steam cleaner, and regularly examine their ring(s) with a loupe... not actually normal consumer behavior. (no offense!)

But during the course of the day, and also when the person trys on the ring in a store, she''ll be looking at it with a tilt.

(JMHO)

Agree to a large extent also even if the table is aligned with the eye the lighting is usually from above or at an angle which also makes a difference.
This is why AGS checks the diamonds at up to 45 degrees of tilt and to get the top score they have to have very good return at all angles.
It is one of the things I really like about the AGS grading system.
Its also one of the things I don''t like about imagem, b-scope, IS with the diamond in a tray, ditto ASET, isee2, all these technologies suffer from it in some way.
IS and ASET can be used while tilting the stone.

For rounds in the ideal range it don''t matter much because of the design of the cut but its critical with fancies.

 

[Paul-Antwerp]

I think that the overall conclusion is that we should realise that there is an over-concentration on rounds in the study of cut.

Devices, simple as well as complicated, are developed to measure or show light performance in rounds, and some of the rules of rounds seem to become overall law. Unfortunately, this does not work completely, when one goes on to look at other shapes.

In this way, it may be good marketing, but the obsession of some to get a H&A-pattern in squares seems incorrect from a scientific point of view.

In the same way, it is incorrect to aim for minimal light leakage in fancy shapes. And an idealscope only gives very limited info on a princess, for instance.

The difficult point is that because of their complexity, we cannot offer the simple assessment-tools that we are used to in rounds. For us, as sellers, that is a problem too, since it takes much longer time to get the message, that we are cutting truly superb fancies, across.

All in all, we should be thankful to AGS for the ground that they have covered, and although, we personally consider their top-grade as too broad, it is by far the best system available at this point in time.

Live long,

 

[WinkHPD]

RE: All in all, we should be thankful to AGS for the ground that they have covered, and although, we personally consider their top-grade as too broad, it is by far the best system available at this point in time.

LOL! I bet that they hate to hear that from you Paul. I think Peter might agree with you from a gemological point of view, but he has a board of directors to answer to that also have diamond cutters to answer to. I am exstatic that he has been able to bring so much to the table so far and look forward to coming developements!

Wink

 

[denverappraiser]

Paul,

Do you have a suggestion of a tool, or even an approach to a tool that would be more useful for analyzing or documenting princesses?

Neil Beaty
GG(GIA) ISA NAJA
Professional Appraisals in Denver

 

[oldminer]

Paul: I quote you, in part: "Untrue, this difference in appearance should not warrant a difference between ''Good'' and ''Excellent +''."


I''d respond by saying that the difference in ImaGem grading between Good, Very Good, Very Good+, Excellent and Excellent +, the five grades I mentioned, is fairly tight grading, not necessarily a wide range. Its that we can discriminate and we choose to do so. The human eye cannot see the difference from Excellent+ to Very Good+, but diamonds are commonly sold with discriminate grades of color and clarity well beyond what the human eye can detect. We want to keep grading sufficiently finely divided for perfomance as other important aspects of diamonds such as color and clarity grading.

xxxxxxxxxxxxxxx

My idea is that one can readily determine which diamonds generally look best without tilting them some undecided number of degrees. Finely cut diamonds look great face up and always allow some tilt without a badly negative effect happening. I''d think one can grade and separate diamonds by light performance based on simple face-up results without resorting to any tilt test at all. What we all want is a simple strategy for telling us when we have the best looking range of stones. I have never seen a diamond that looked only fair face up that looked far better when tilted. I doubt anyone would opt for such a stone or pay a premium for such a cut.

We definitely agree that consumers and dealers may prefer diamonds that don''t have the highest measures of light performance. Some people may prefer more contrast and less overall brilliancy. Different shape diamonds have different best measures of the characteristics, too. Not everything is being compared to round diamond performance standards. ImaGem was prgrammed separately for princess cuts without regard to round diamonds.
xxxxxxxxxxxxxxxx

Paul, I quote again: "Imagem gives uncomfortable results on Princess-cuts"

I truly believe on this you are ill informed or it may be a language problem. If you are uncomfortable with the results, it may be from lack of familiaritywith the ImaGem measures. These measures while elegant and simple, do describe light performance very well when it comes to diamonds. If we need to tilt diamonds to determine performance, then we do have an issue that is unresolved, but I''d contend that tilting is not the way to grade diamond performance. I believe more comfort with these results will arrive in short order. We recently processed several thousand princess cuts for a SightHolder and major US retailer. Now, these were not AGS 0 types, but more normal cut princess stones. The results made no one less than confident or uncomfortable. This kind of volume will have an impact on how diamonds will be graded for major retailers and SightHolders. Time will provide us more comfort, I hope.

 

[strmrdr]

This thread is giving me flashbacks.
When im feeling better I will hunt down the earlier princess thread where this was discussed with the b-scope.
Measuring light return in a fixed position doesnt mean as much with fancies.
When Jon stopped using the B-scope to select asschers is when he finaly got them and learned to select the best of the best.

From what Iv been hearing its the same with the new style princess cuts.
AGS threw out the rule book when they designed them.

 

[JulieN]

Date: 6/12/2006 5:27:03 PM
Author: strmrdr
...the earlier princess thread where this was discussed with the b-scope.

https://www.pricescope.com/community/threads/ags0-princess-cuts.34950/= ?

 

[strmrdr]

Date: 6/12/2006 5:32:46 PM
Author: JulieN

Date: 6/12/2006 5:27:03 PM

Author: strmrdr

...the earlier princess thread where this was discussed with the b-scope.

https://www.pricescope.com/community/threads/ags0-princess-cuts.34950/= ?

Thank you thats one of them :}
There is also another one that is more in depth I think but I could be remembering wrong.

 

[Paul-Antwerp]

Date: 6/12/2006 4:48:54 PM
Author: denverappraiser

Paul,

Do you have a suggestion of a tool, or even an approach to a tool that would be more useful for analyzing or documenting princesses?

Neil Beaty
GG(GIA) ISA NAJA
Professional Appraisals in Denver

I wished that we had a tool or even an idea about one tool. It would make education and resulting sales a lot easier.

At this point in time, one can only use a series of tools, while making sure not to put too much weight in one single tool:

1. As a start, getting stones with an AGS-grade on light performance is fantastic. One does not get these grades by accident. Therefore, do not expect to find them in non-AGS-graded stones. It will be like finding a needle in a haysteack (spelling?).

2. The H&A-view of a princess will show you its symmetry. Do not look for arrows, or hearts, look for a symmetrical built-up. Symmetry is always the key to light performance. I am sure that non-symmetrical light performance exists, but cutting planned asymmetry is extremely difficult and unlikely.

3. In the Idealscope, look for a nice contrast-pattern, without aiming for the total absence of light leakage.

4. In the ASET-scope, look for that same pattern, and a good division of reds, greens and blues.

5. When assessing a Sarin- or Helium-measurement, make sure to get all the figures, and forget about the averages. In princess-cuts, cutters are used to ''following the rough'' and ''cutting for weight''. A P1-angle of 64° might mean two angles of 66° and two of 62°. If possible, you should check all the angles, starting with the pavilion, since this is the foundation of light performance.

6. Do not forget the ultimate tool: your eyes.

Live long,

 

[RockDoc]

RE: Bscope analysis of princess cuts.


The software for different analysis by shape differs between the shapes "read" by the B Scope. Substanciation of this is readilly available to those of us who have the machine, by changing the shape, and looking at the "blue bar" rating, to see how the results vary. The largest volume of imaged stones are mostly rounds with princess being second in the number of imaged stones. Totally this is now over 1 million stones that have been imaged. Currently it does a fairly good job recognizing rectangular stones as well, but pears, marquises, ovals and other various shapes don''t have the depth of volume testing results they are present with rounds, square, and rectangles.



The results by using the "blue bars" differs, but what the machine "see" in its images, it really doesn''t care.

If you put in a dead elephant''s foot, it simply measure the return of white light, color light, and scintillation ( which does have a tilting factor built in the program). The machine does not Discriminate between materials or shape when you examine the graphical images.

You put in something that doesn''t return light, the Bscope picks that up.

Rockdoc

 

[Rhino]

Good thread Dave.

I''d like to add some input here and my experiences with the varying flavors of AGS Princess Cuts I''ve been seeing and the corellations I''m noting between our technologies (Imagem & BrillianceScope and also reflector types).

Date: 6/12/2006 8:39:42 AM
Author:oldminer
We have seen a few AGS 000 princess cuts in past months and have found that ImaGem measures their light return and performance over a fairly wide range from as low as ''Good'' to Excellent+'' A range of 5 grades in the system we use. One might choose to have a less disciminating system, but regardless of the system, there is some visible difference in performance of these AGS 000 princess cuts.

I''ve noted the same thing.

First and foremost, all of them looked quite lovely, so the news is not bad. However, as measured performance declines, the stones do appear to look somewhat different. Beauty is the choice of the consumer and dealer. A machine does not dictate what one might judge best for their own taste, but for engineer types performance with higher numbers must be handled. So many Internet shoppers are numbers people, we need to address the issue.

Garry Holloway spoke to me about what may be taking place with ImaGem and its measures on Princess cuts. He tells me that some of these AGS 000 diamonds require tilting to perform their best. In fact, the essence of what he said would indicate to me that they don''t perform as well face up as they do at some degree of tilt. I am simply amazed by this. My personal logic tells me that face-up is of utmost importance in grading diamonds. This is from years of experience, not just a traditional viewpoint. If some AGS 000 princess cuts look better when tilted than they do face-up, then they do deserve a lower resulting cut performance grade....At least that''s what I think is right.

I''m with ya on that. IMO, Face up appearance is key. Something I''ve been noting however is that these same stones that don''t face up as nice don''t appear to be any better when tilting it either.

Maybe someone with more experience with the AGS 000 princess cuts will have a differing point of view or different information they wish to share. I''d sure be glad to know why the light return is not judged face-up as the primary grading characteristic. All opinions appreciated.

I believe the face up appearance is definitely being considered as the primary element in the AGS system but I also believe with it being a. new and b. the first lab to implement cut grading for princess cuts, that the system isn''t as tight as some of us would like.

Regarding BrillianceScope and it''s relation to all of this I''d like to share a bit. I read strm''s response regarding some of the things we''ve found regarding BrillianceScope and how sometimes the coreallations to human observation didn''t line up but I''d like to expound on this a tad because we''ve discovered another little shortcoming regarding the Bscope which may or may not apply to the Imagem.

Firstly, with the princess cuts that I''ve sent to you for Imagem testing it appears the Imagem works most similarly to the Bscope than the other technologies we employ. Please correct me if I''m wrong Dave but it appears the Imagem is taking a measurement of light from the diamond based on direct light testing as opposed to diffuse light testing. I assume this becuase the stones we have sent in the past all corellated with BrillianceScope results so there are definitely similarities/corellations there.

Now ... in most circumstances BrillianceScope results do indeed corellate with human observation with regards to viewing diamonds in direct light environments. In the past (and even currently) our purchasing has primarily centered around stones with the rarest results. With the release of AGS cut grading for princess cuts and also GIA''s for rounds we''ve run into 2 instances so far where human observation ran counter to the technologies. With princess cuts it was a stone that got a low/medium/low vs a 2/3 VH''s (and the observation results were about 50/50). The 2nd instance with the rounds was a GIA Ex steep/deep vs an AGS Ideal that didn''t make GIA Ex grade (and the observation results in that instance was 90/10 in favor of the GIA Ex).

These results caused me to further investigate the *why''s* which caused me to discover this other lil shortcoming which turned out to be the angular spectrum range used by the Bscope to determine its scores. You see, the Bscope is drawing it''s light readings from an angular spectrum from 36 degrees off the horizon up to the perpendicular of 90 off the table.

To better visualize this ...

If you made an ASET demonstrating this, the green would be from 0-36 instead of 0-45. What this means is that the Bscope is measuring light return from a narrower angular spectrum. So, diamonds that may perhaps be drawing light from the 36-45 degree spectrum are taking a hit in the BrillianceScope *unduly*. Which leads me to this question Dave. From what angular spectrum is the Imagem drawing its readings from?

One other note ... while strm has pointed out that the AGS Princess cut we ran the observation testing on was favored equally in our survey, another recent acquirement doesn''t and is notably less bright and less fiery and the Bscope results corellate. Perhaps i can videotape the 2 stones I''m talking about for a demonstration. I look forward to hearing back from ya.

Peace,

 

[oldminer]

Dr. Aggarwal has replied as follows:

I am not sure what is the definition of "direct" and "diffused" light used by "Rhino".
The lighting environments used by ImaGem and Brillianscope are different in many ways. The angle of incidence of the light with respect to the table with ImaGem is as broad or more broad than the angles used in Gemex. To establish statistical correlation, one must have a representative and a large sample. A true study comparing the performance of different systems on light behavior has yet to be conducted.

What can be demonstrated using ImaGem's technology is that light performance
of AGS 0 stones varies significantly on the measures of light behavior
developed by ImaGem for Princess cut. Furthermore, the differences in the
light behavior of AGS 0 Princess cut are large enough that they can be
easily perceived in their images. These are important findings and require
careful review of the cut grading system developed by AGS and the impact
direct measurement of light behavior is likely to have on the cutting,
grading, selling and valuation of Princess cut stones. For example, are
there non-zero AGS stones which have better light performance than AGS 0 cut
stones? One might pose several other questons.
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

The direct, diffused lighting question is answered in this way.

ImaGem uses direct, diffused lighting.
Gemex uses direct, non-diffused lighting.

Lighting types may be indirect or direct. Each of these two types may be non-diffused or diffused.

If a question about this remains, please let me hear from you.

 

[Paul-Antwerp]

Date: 6/14/2006 12:58:11 PM
Author: oldminer

These are important findings and require
careful review of the cut grading system developed by AGS and the impact
direct measurement of light behavior is likely to have on the cutting,
grading, selling and valuation of Princess cut stones. For example, are
there non-zero AGS stones which have better light performance than AGS 0 cut
stones? One might pose several other questons.

These are important findings and require careful review of the grading based upon image-processing as being used in the Imagem-system.

First major question: Is this way of direct measurement of light behavior indeed a direct measurement of light behavior?

Live long,

 

[researcher]

I just wanted to say I'm learning a TON from this thread. Please keep up the discussion! It's nice to have the true experts considering the consumers' perspective and tools for performance measurement

 

[oldminer]

Paul, with no disrespect to you, the answer is that the image processing and the measure of light behavior derived from it is known in the scientific world as Imagestatistics. This is a discipline of science that Dr. Aggarwal brought to the scientific community some years ago. I believe he knows when he is measuring something with digital processing having his extensive background and expertise in digital imaging and statistics.

 

[Paul-Antwerp]

No disrespect here, either, Dave,

But a 10-inch ruler will work perfectly when measuring a line of 5 or 6 inches, but if you want to measure a mile, it will be ineffective.

Now, the ruler is perfect, and scientifically so, for measuring lengths, still it is not the adequate tool in this instance.

Live long,

 

[oldminer]

Paul: We have a high precision 12 inch ruler and are measuring nothing exceeding 10 inches. I think we have the tool for the job. The entire process has been controlled so that no diamond can possibly measure greater than the ability of the device to discriminate performance. Performance does not totally equate to every individual's human preference of what is most beautiful, but we believe that all the most beautifully performing stones will score in the upper category of the system proposed. Some consumers may select a diamond from a lower category, but this may be not only personal preference, but a budgetary or weight preference. Whatever they wish to purchase, knowing all the facts, is fine with all of us. I would think engineers will probably go for the highest performance numbers, but most people who are less number conscious will use their eyes, wallets and other faculties to make choices more in moderation yet still in the top two or three categories.

Nothing to date with thousands of test stones measured indicate any problem with this ability to measure brilliancy, sparkle and intensity as defined by ImaGem. I would further warn people reading our little discussion that we personally get along nicely and that this is a discussion of importance, not a minor fight.

I am far more concerned about the world of diamonds being upset with utilizing measuring devices that don't measure all that well, then rounding off these somewhat faulty results and then giving total reliance on a final prediction based on poor science, poor measures and quasi-visual results to confirm the whole mess.

 

[Rhino]

Date: 6/12/2006 11:56:16 AM
Author: Paul-Antwerp

We ourselves have learned more this last year on cut from studying princess-cuts than we ever could from studying rounds. I welcome others to join us in this field. You will quickly learn the limitations of your current knowledge.

Ain''t that the truth. In the above comparison that strm talks about, one other element was the fact we were not only comparing 2 stones of AGS Ideal status with varying BrillianceScope results but also the amount of chevrons on the pavilion. One was a 2 chevron stone and I believe the other was a 3 which alters the appearance of the stones as well. In that comparison we found the fewer chevrons contribute to a different appearance regarding brightness/contrast. An element the Bscope meters do not see in their scores, yet can be assessed in light view 6.

 

[Rhino]

Date: 6/12/2006 4:43:40 PM
Author: Wink
RE: All in all, we should be thankful to AGS for the ground that they have covered, and although, we personally consider their top-grade as too broad, it is by far the best system available at this point in time.

LOL! I bet that they hate to hear that from you Paul. I think Peter might agree with you from a gemological point of view, but he has a board of directors to answer to that also have diamond cutters to answer to. I am exstatic that he has been able to bring so much to the table so far and look forward to coming developements!

Wink

Haha... amen and amen!

 

[He Scores]

RE: Light study of face up views.

It''s been my contention all along regarding "look grades" that the diamond is a piece of sculpture. Name me one other piece of sculpture in the world of art that is viewed in only one position, in a certain lighting environment.

Diamonds of all shapes are viewed by the wearer in all sorts of directions.

Frankly, I felt most of the studies limiting the observer or observing instrument to the "face up" view was.....limiting.


Bill Bray
Diamond Cutter

 

[strmrdr]

Date: 6/12/2006 6:30:31 PM
Author: Rhino

One other note ... while strm has pointed out that the AGS Princess cut we ran the observation testing on was favored equally in our survey, another recent acquirement doesn't and is notably less bright and less fiery and the Bscope results corellate. Perhaps i can videotape the 2 stones I'm talking about for a demonstration. I look forward to hearing back from ya.


Peace,

That supports my 2c that pixel counters no matter the light type aren't reliable indicators of princess cut beauty.
I will state for a fact that that is true with asschers that they arent.

 

[strmrdr]

Date: 6/14/2006 8:40:39 PM
Author: He Scores


RE: Light study of face up views.


It''s been my contention all along regarding ''look grades'' that the diamond is a piece of sculpture. Name me one other piece of sculpture in the world of art that is viewed in only one position, in a certain lighting environment.


Diamonds of all shapes are viewed by the wearer in all sorts of directions.


Frankly, I felt most of the studies limiting the observer or observing instrument to the ''face up'' view was.....limiting.



Bill Bray

Diamond Cutter

AGS agrees with you, they grade from 0 to 45 degrees tilt relative to the light source.

 

[JohnQuixote]

Date: 6/12/2006 8:39:42 AM
Author:oldminer

Maybe someone with more experience with the AGS 000 princess cuts will have a differing point of view or different information they wish to share. I'd sure be glad to know why the light return is not judged face-up as the primary grading characteristic. All opinions appreciated.

Great thread Dave.

Rounds are the most optimized shape for light return. As such the static view is appropriate. On the other hand, in fancies the look changes more in dynamic situations.

IndieJones voiced this nicely from a consumer perspective.

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?

 

[JohnQuixote]

Date: 6/12/2006 11:56:16 AM
Author: Paul-Antwerp

We ourselves have learned more this last year on cut from studying princess-cuts than we ever could from studying rounds. I welcome others to join us in this field. You will quickly learn the limitations of your current knowledge.

Ditto that. Our own AGS0 princess has taken time to develop because so many combinations are possible. It’s like a treasure hunt for gold, but when you ‘struck it rich’ you don’t find just gold, you find it and other, different kinds of treasure… Of course you can’t weigh it all as if it were just gold.

What we have learned (some old, some new):

1. A narrow range of performance expectations cannot be applied to princess or other fancy cuts as we do for round stones.

2. When dynamic (in motion) each cut takes on a different personality that can’t be evaluated in the static view.

3. Greater opportunity exists for different tastes, especially within varieties of configurations like the ones AGS has worked with us on (different chevrons, crown faceting, etc.).

4. Humans see differences in top-performing cuts and find several ‘looks’ equally attractive.

…Oh, and there is also this little thing called ‘lighting.’

Mechanical and other approaches can make valid interpretations, but each is equipped to handle measurements in just one way. Using Paul’s ruler comparison, we have several rulers available to help us.

+ AGA and similar charts are good guides.
+ The Ideal-scope view is wonderful.
+ The ASET view is even better.
+ BS and Imagem are developing measurement technologies that are adaptable.
+ DiamCalc is invaluable.

But only human cognition can reconcile so much, and juxtapose it with taste.

No doubt we’ll continue to work to build a better mousetrap.