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ImaGem Light Behavior scores for round diamonds

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oldminer

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Excellent Very Good Good Good to Fair Fair Commercial
Brilliancy 140 & up 120 to 139.9 110 to 119.9 100 to 109.9 80 to 99.9 0 to 79.9
Sparkle 60 & up 40 to 59.9 20 to 39.9 10 to 19.9 5 to 9.9 0 to 4.9
Intensity 145 & up 125 to 144.9 115 to 124.9 110 to 114.9 105 to 109.9 100 to 104.9

The numeric readouts are a result of Direct Measurement. The words we apply to them are interpretations based on appearance and a subject to future minor revision. The numbers are solid and no change is anticpated, so if you get a diamond that rates 150 brilliancy, 59 Sparkle and 210 Intensity it will always score relatively identical measurements regardless of any words gemologists may choose to attach to those numbers.


PLEASE SEE MY WEBSITE FOR ALREADY REVISED NUMBERS>>>>> We knew this might be necessary, and it was. 8/1/2005
 

Regular Guy

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Dave,

I'm anticipating this question will either not interest you, or you'll be ambivalent about the answer...but here goes...

I'm wondering what relationship may exist between your output of scores, and your otherwise developed cut classes (where, by the way, I think Pricescope has perhaps not cleaned up the data on depth for AGA 1A yet).

Just curious.
 

oldminer

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The 1A rounds will all have very good scores. I'd be surprised if those combinations fail to make very attractive diamonds. Beyond that, I think one would be better off with an ImaGem score and a newer AGA-DFS cut grade combination. The old AGA-Cut Classes are okay for screening but will be surpassed by Light Beharvior scoring measures, so long as one still keeps their eye on dangerous cut parameters and looks out for overly deep diamonds. If one is to get the best value and total appearance for their money, a diamond should be durable, look its weight and have no visible finish flaws.

Leonid has now fixed the small error that was on the Pricescope version of the AGA round Cut Class chart.....THANKS>
 

strmrdr

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Leaving aside the unknown light envirement and other problems for a second.

Where does a difference in score actualy become eye visible?
1 point? 10 points? 20?
 

oldminer

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"It would be great to see some of the proportion variants of stones that rate from each grade Dave"

If you would arrange for stones of your chosen variations to be sent to us for such a study, it would only take a day to run them and return them. We''d absorb all shipping costs both ways. We are totally ready and working for rounds and only about 30 stones away from being fully ready on princess cuts.

As far as where does eye visiblity of differences come into play, I don''t want to be evasive, but we all perceive differences differently. Diamonds are constantly graded and marketed by variations that are invisible to the unaided eye. This is mirrored in the Light Behavior of ImaGem measures. Stones which score very high are visibly better than average stones. Where the ability to see a difference occurs would be speculation. When one seeks the best, eye visiblity is hardly the deciding factor. Diamonds that score "GOOD" look very nice even to my own eyes. While they do not look like the best stones, they are not bad looking or ugly. These measures are quite precise and repeatable, but I would say that in the upper ranges the degree of eye visible difference is nominal and not readily visible with the difference of only 1 to 10 points of the index. At the very low end, the spaces are fewer and the grading is therefore coarser. Of course, at the low end, no one much cares about performance. Then it is size and price.

Although I can''t tell you the exact lighting model, I will assure you it is not very high tech or weird. It mimics actual lighting situations.

ImaGem has a large willingness to show how their tool grades diamonds predicted by other labs to be brilliant. I am willing to finance the shipping and to share the results so long as the predictive model results are provided to ImaGem. This is sharing to increase accuracy and knowledge, not to compete in some unfair way. Fairness is one of the main goals.
 

Garry H (Cut Nut)

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Have you checked the diamonds clean and dirty Dave?

e.g. does a very high scoring tolkowsky stone score Excellent and then drop to Good to Foor when dirty.
A slightly deep steep stone that scores Very Good when clean- does it drop to Fair when dirty
And a shallow stone that scores Very Good clean - does this stone drop to Good to Fair?

It would be a good test for a theory of mine
 

strmrdr

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Im not sure how to word this:
What is the relationship between Brilliancy, Sparkle and Intensity.
ie:
will a high scoring stone in brilliancy also score high in intensity or is it possible to have exellent in one and fair in another?
Same with sparkle vs brilliancy and intensity.

If a stone was strongly tuned for colored light return over white light return what would the expected relationship between Brilliancy, Sparkle and Intensity be?
Same for one tuned for white light return over all else?
 

Paul-Antwerp

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David,

I think that you have explained before, but could you repeat it here: What do the terms ''brilliancy'', ''sparkle'' and ''intensity'' exactly stand for in Imagem?

Live long,
 

oldminer

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The definitions of the terms are found in the reference section of the Pricescope Journal. Simple and more complex ones.

A dirty diamond will have a lower set of readings. Exactly how the relationship of the numbers changes I could not predict, but something that masks the stone will certainly alter the performance. That is part of the point in measuring rather than predicting the performance.

Strmdr: You ask the hardest ones. I will try to give you a responsive answer. 1. Remember, above all, this is diamonds we are discussing, not hypothetical situations of all materials. Diamonds with high brilliancy will probably have better sparkle and Intensity because they are well cut and working toward the goal of overall beauty. If you could make a diamond mirror with only 1 huge facet it could reflect a lot of light and be brilliant while having no sparkle and little intensity. Now, that wouldn''t be a normal diamond so I expect we won''t actually see it.

The numbers are related, but do not rise and fall in unison with every reading. We have seen diamonds that look good that have differing readings. High performance is clustered in certain relationships of Brilliancy, Sparkle and Intensity. Because diamondsa are faceted and generally cut in similar manners, the numbers work more or less together. In a hypothetical world, one might find high brilliancy and good sparkle with little intensity, but I doubt one would find that in a standard cut of diamond. Cutters are too skilled and too smart to make stones that way. I hope you find this a decent answer.
 

strmrdr

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Date: 5/3/2005 6:59:55 AM
Author: oldminer
The numbers are related, but do not rise and fall in unison with every reading. We have seen diamonds that look good that have differing readings. High performance is clustered in certain relationships of Brilliancy, Sparkle and Intensity.

Im trying to get a handle on how to properly apply the readings.
As with the other machines there are going to be diamonds that due to their personality
score in way different ways but some people may prefere them over one that scores off the top of the scale in different areas.

For example some people will prefere diamonds that tend to score H,VH,H on the b-scope over ones that score VH,VH,VH because they like the firey look.
While technicaly they dont produce more colored light return to the eye they do.
 

oldminer

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To ImaGem and to me, we do not intend to provide a colored light return score. All light return is brilliancy. It is possible to measure colored light return, but this is a factor which varies greatly in different lighting conditions. It is not a factor, we believe, in determining the overall beauty of a diamond. Sure, one can measure it. One can measure many things, but not every measure means anything or means much. Fire, colored light return, is one of the things that greatly varies in every diamond depending on the light environment, but does not control overall beauty judgement....so we believe.

One can love a diamond that does not score as well as another. We do not all select the most beautiful people based on what others judge, but upon our own set of values and personality. No one says a super high scoring diamond won''t be beutiful, but someone might well select a somewhat lesser performer simply because they like it better.....We may or may not agree...That''s okay.
 

strmrdr

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hmm im not sure I agree with dismissing colored light return as separate.
It plays a huge part in what makes one super-ideal look different from another and looks different to the eye than white light return.
Some people like the bright look some like the firey look.
The relationship of white light return and colored light return often defines a huge part of the personality of a diamond that makes one diamond "speak" to a person over another from what Iv seen myself and learned from others.

While I can agree that colored light return is defendant on the lighting the cut can affect under what conditions it is displayed and the amount of fire vs white light return.

From a technical standpoint I can see the position of light return is light return but im not sure how that will play visually.
It could be that the light conditions it measures under dont produce fire then measuring it will be irrelevant.
The more I try and wrap my head around what its doing and where it fits in, the more it keeps coming back to light conditions/light model.
 

oldminer

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I can accept that not revealing the exact lighting model has created both curiousity and questions from knowledgeable thinkers on this subject. What I have been told to offer is the opportunity to these folks so that they may test diamonds of their choice to satisfy themselves that the system grades properly and discriminates well.

Ultimately, the fact that a system works well is the proof one seeks. We can set up hypothetical situations from now to the end of time, but it gets us nowhere. Here we have a device, created by a team of experts in human perception and also in technology. Their claim is that it can give us direct measurement of the three most important and repeatably reliable charactertistics of Light Behvior in diamonds. From my perspective it is doing what they say it is supposed to do. The variations in readings are nominal and diamonds with visibly different levels of beauty are well discriminated. Although I can''t see it, the measurement of variables that can''t be seen with the unaided eye appear to be repeatably measured. This fits exactly along the lines of how we grade diamonds for color and clarity.

The testing of a few round diamonds is most welcome and will cost the source nothing. We''re glad to report the ImaGem results so long as any other major lab grading reports related to these diamonds are shared with us.
 

He Scores

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Gary,
I''m curious about your theory on the dirty diamonds. I think you''re on the right track. I''ve always said that it was a leap of faith to jump from a good "performance" grade equalling a good "cut" because there are several other factors that affect how a diamond "performs" other than cut.


Bill
 

oldminer

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The very first thing one does before beginning the process is to make sure the diamond is as clean as possible. Just as we already know with our eyes how a dirty pavilion hurts the light performance, the ImaGem device will also measure the same. While fine performing diamonds are less bothered by dirty build up, they are hampered in performance by it. We already know that. There is no reason to asssume that the ImaGem will see anything else. Again, we are MEASURING actual light performance, not calculating it based on cut parameters.
 

JohnQuixote

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Dave, how have you found repeatability to be on the machine in your lab when running the same diamond? Also, have you had a chance to run a diamond on your machine, then on a second unit to check repeatability?
 

oldminer

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The repeatability issue was addressed early on. It repeats and repeats on other machines at the home office of ImaGem. Without that repeatability, the process would not be valid. Of course, there is automatic calibration built into these devices and a morning check before we proceed with processing. I believe this part of the process is pretty much trouble free. There was great care taken in calibration and also in the selection of the light sources used.
 

JohnQuixote

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Dave, I recall those assertations and was hoping you could offer personal input, since you have been working with your own machine for some time now. It sounds like you''re saying that when calibration is good your own machine does well with repeatability, right?

The other curiosity I had was whether you have actually had the chance to compare test results between a single diamond on your machine as well as at the home office.

An aside re: measurements - the fact that it is able to measure to within 0.005 mm is terrific.
 

oldminer

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DIamonds have been measured in our office with total repeatability and then taken to the ImaGem office where they measure exactly the same....within the range of known machine error. The lighting is VERY precise and the light sources are a known commodity. This is not being left to chance.

Physical measurements of diamonds above .40ct are quite a bit more precise than .005mm. The device can reliably measure to 4 decimal points, but it seems terrible overkill to report such numbers on our grading documents. At 3 decimla points, there is no variation, or rarely any. I can''t remember a stone that varied in lenght or width when the normal calibration regimen was followed at the beginning of the day.

If one wanted to grade many diamonds below .40ct with the same degree of accuracy found for larger diamonds, some alteration of the camera lens would be in order to get more precise measurements. I think it is not as important on small diamonds as it is on larger ones and it does simplify the product. ImaGem can build a model with extremely high precision for small diamonds, if someone wanted it. There is no technical hurdle, just a mtter of someone needing it.

Light behavior measures for small diamonds seem to need no adjustment for size.
 

Regular Guy

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Dave, Rock Dock, Jonathan, and all,

Also, though this mostly follows up your related query today, Dave, I have a few questions here also intended to:

a) be associated with today’s discussion of branded options, and they’re also directed to:

b) Rock Doc, Jonathan, and anyone who will have had an opportunity to watch correlations between measuring devices that count success (or lack thereof), and the diamonds those numbers are associated with…

Setting up scales so that the change from one “level” to another is meaningful, is probably always, both a challenge, and an art. (I suppose, having a metric measure something that will helpfully differentiate is another). I presume, Dave, that you note at the top of this thread that you revised your numbers because such a change was thought to be necessary, based on the pattern of the groups of diamonds your numbers were describing.

So, for your scales, Dave, or for categories the Brilliancescope or ISEE come up with, any sense about what percentages these categories will factor into? At least, for those diamonds you yourself see.

Has anybody, either on the back of an envelope, or more formally, been watching the categories of numbers that branded options fall into? Perhaps my suggestion that appraisers keep these guys around will not be necessary, if their scores can stand in for them?

GIA’s assertion is simple enough to understand in principle…find variations in measurement for different diamonds, and then…don’t categorize those patterns, but categorize people’s reactions to the patterns. At least, that’s the idea. With respect to the data collected by these devices, whereas the capture is linear, are the reactions observed by those who seen them consistent with these scores, i.e. do people consistently prefer the higher numbers on the devices? Are the bands established consistent with these reactions, or with some ostensibly more objective measurement, which we should then discount, if the objective measurements don’t conform to the pattern of human observation?

Can a shopper reliably have an agenda to make a purchase based on finding a diamond that performs above a threshold. To you appraisers…do you see any of your customers coming to you with that sort of agenda?

Thanks for your indulgence, in the questions prompted for me in today’s discussion.
 

RockDoc

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Date: 8/16/2005 4:54:46 PM
Author: Regular Guy

Dave, Rock Dock, Jonathan, and all,

Also, though this mostly follows up your related query today, Dave, I have a few questions here also intended to:

a) be associated with today’s discussion of branded options, and they’re also directed to:

b) Rock Doc, Jonathan, and anyone who will have had an opportunity to watch correlations between measuring devices that count success (or lack thereof), and the diamonds those numbers are associated with…

Setting up scales so that the change from one “level” to another is meaningful, is probably always, both a challenge, and an art. (I suppose, having a metric measure something that will helpfully differentiate is another). I presume, Dave, that you note at the top of this thread that you revised your numbers because such a change was thought to be necessary, based on the pattern of the groups of diamonds your numbers were describing.

So, for your scales, Dave, or for categories the Brilliancescope or ISEE come up with, any sense about what percentages these categories will factor into? At least, for those diamonds you yourself see.

Has anybody, either on the back of an envelope, or more formally, been watching the categories of numbers that branded options fall into? Perhaps my suggestion that appraisers keep these guys around will not be necessary, if their scores can stand in for them?

GIA’s assertion is simple enough to understand in principle…find variations in measurement for different diamonds, and then…don’t categorize those patterns, but categorize people’s reactions to the patterns. At least, that’s the idea. With respect to the data collected by these devices, whereas the capture is linear, are the reactions observed by those who seen them consistent with these scores, i.e. do people consistently prefer the higher numbers on the devices? Are the bands established consistent with these reactions, or with some ostensibly more objective measurement, which we should then discount, if the objective measurements don’t conform to the pattern of human observation?

Can a shopper reliably have an agenda to make a purchase based on finding a diamond that performs above a threshold. To you appraisers…do you see any of your customers coming to you with that sort of agenda?

Thanks for your indulgence, in the questions prompted for me in today’s discussion.

Very intereting questions, Ira.

Unfortunately, it is one where we don''t have a 100% constantly occuring statistic to report.

I am not sure the correlation between measured light performance, calculated light performance and attractieness will ever be 100% reliable based on proportional numbers.

There are just too many other factors that can affect this, and to make statements that a consumer would think are conclusive is just hype.

Diamonds are ( as all gemstones ) little individual creations of Mother Nature. As I have written before - Mother Nature Fickle finger of Fate ( i.e. usually the middle finger with a long sharp fingernail) shows us that just when you think something is totally consistent, it turns out not to be.

Another factor in diamond light performance and calculation ray tracing predictions is the type of stone, the size of the stone, length to width ratios, light absortion, sight preferences, inclusions, graining, orientation and much more.

Now if some computer whiz can program all the factors in to some future kind of software, then maybe it will be possible, but as of now, basic assumptions, considerations of multiple testing, and very advanced examinations is the best I believe that is available.

There is not easy - automatic basis of comparison that is totally reliable without experienced human particpation along with the tech stuff.

Rockdoc
 

Regular Guy

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Not sure what to say.

Locally, the Realtors who get my attention are not the ones who have a picture of a house, and tell me: I'm selling this, you wanna see it? They're the ones who provide me analysis, telling me that these many houses in these zip codes sold for this amount, and wouldn't you like to know I crunched those numbers?

Dave, you've said:

"I know the black box objections by now pretty well as I have a black box. I won't argue that you and others are very right in being suspicious. It would be foolish for an uninformed person or group to jump on board without sufficient proof. Please let's dream for a moment, get hypothetical and ask if one did use such a black box to make accurate, reasonably narrow and visually meaningful categories out of what is already out there, wouldn't that be a practical and consumer friendly improvement? There are a lot of existing diamonds needing analysis."

In contrast to my friend Storm's contention, perhaps you've created this very device. Can't you bundle some data for us? Particularly regarding branded options, are there no patterns regarding performance that you can report on? Or are you just not doing that analysis?

And Rock Doc:




Date: 8/16/2005 5:52:08 PM
Author: RockDoc




Diamonds are ( as all gemstones ) little individual creations of Mother Nature. As I have written before - Mother Nature Fickle finger of Fate ( i.e. usually the middle finger with a long sharp fingernail) shows us that just when you think something is totally consistent, it turns out not to be.
Really, Rock, one is left with the impression that you may eat this sort of data for lunch; you report that you collect data on stones, whether or not your client asks you to do this or not. Your comment above about individuating per diamond is convenient, but does not serve someone who wants to take advantage of the very type of tools you offer. Is it simply unknown to you about bands of data, how they present, and the percentages they fall into? You say the questions are interesting; aren't the answers interesting, too. Mainly, the thing is...why bother to purport there is no 100% correlation, since we can guess as much. What patterns of data exist, and surely we can determine, if it is the case, that it is chaotic, or that instead there is a pattern to observe.

Well...true enough...were I shopping for a Realtor/appraiser, on the basis of data collection, there's just not a lot of appraisers to turn to that do any sort of this sort of data analysis to speak of, anyway. That the (mostly) gents on this board who appraise, and report to us about the results of this work, is appreciated. I guess, just like the kid in the story says: "I want some more."

Regards,

P.S. Just to follow up, and for any of those appraiser/doubting Thomases, whether or not you employ these measuring devices...would you find value in having in your possession not numbers, but actual branded options, that you could show to your clients, were they interested, to give them an idea of the options for performance that exist out there, should they not purchase option (a) they came in with, but might want to explore in option (b).

And, to an appraiser's customer...would such a feature be attractive to you...to have a branded option to look at, and compare your option to, that you've come in with?
 

oldminer

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We have been grading round, standard brilliant cuts. I believe we could compare these to branded, modified brilliant round cuts with little problem or delay. One never is totally sure until it is tried a few times. We have not done that testing, but have stuck with standard cut diamonds, so far.

I think we have lots of people more interested in having asked their favorite set of questions than really studying or researching possible answers. There are some notable exceptions to this comment and many good reasearchers are on pricescope and participating.
 

Regular Guy

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Date: 8/17/2005 12:42:59 PM
Author: oldminer
We have been grading round, standard brilliant cuts. I believe we could compare these to branded, modified brilliant round cuts with little problem or delay. One never is totally sure until it is tried a few times. We have not done that testing, but have stuck with standard cut diamonds, so far.

I think we have lots of people more interested in having asked their favorite set of questions than really studying or researching possible answers. There are some notable exceptions to this comment and many good reasearchers are on pricescope and participating.
Dave,

Sorry to have been unclear; I was using branded with the convention that was used yesterday (where you participated, too), to include, in fact, round, standard, brilliant cuts -- and particularly some of popular ones reviewed on this board, and with excitement, frequently, such as WF''s ACAs...you must surely get a number of these. And, also, similarly, options from Infinity, Eightstar, Superbcert, and such. Particularly on this board, it seems to me, although other options are also clearly available, I think many of us are interested to know how these will compare to what we could otherwise find, with what we could call a medium premium paid for the sort of "branding" associated with these named here.

Two other points...

on your survey yesterday, and with reference to the question of whether broad or more tightly titrated categories are most helpful...my feelings are similar to the GIA categories...with the data available, the categories really won''t matter that much. For example, GIA will now give crown & pavilion angles, so we can do our own categorization...at least inasmuch as such data will allow us to do this accurately (today, Rockdoc helpfully gave his opinion that such proportion data will tell 70% of the story, in his opinion). Likewise, it seems your Imagem and light performance based system gives numerical data as output, that you''ve assigned categories to. But, this data, I assume because of it''s linear presentation, you can, at least consultatively, infer grades within the categories (since, as you present initially in this thread, an intensity of 210 must surely be better than the 145 threshold you set out for excellent). But, to do this interpreting successfully, until we have some sort of comparative data, as could be available, we could only guess about optimal performance.

Or...how optimal is excellent, as we currently have it. On this board, frequent talk is how AGS has "got it down" for pedigree, and with GIA, excellent may be all over the place. Given your existing scale, is Imagem -- with respect to light performance, and the category of excellent -- closer in analysis to one of these two systems than the other?

Finally, though, re your last point, sorry, yes, I''m full of questions, and with no answers, at all. So, your indulgence is especially appreciated.

Regards,
 

oldminer

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I want to express that ImaGem and myself feel there are many potential sorts of beautiful configurations, none of which should be graded as superior to another, but all deemed pretty much equally worthy of the title "super performing" "among the most beautiful", "among the best for their shape", etc. While we do have overall light grades of EX+, EX, VG+, VG, GD, GF, FR and CM there are gping to be many of the finest cuts you mention in the EX+ and EX range and we won't really make that judgment of which one is BEST within each category. We will say that EX+ is a little bit better than EX, but probably people won't see the difference if they grade close to the borderline. All borderline cases are by nature sort of arbitrary. We'd like to make a borderline and stick with it for consistency's sake. We also want it to be correct and meaningful. It isn't just throwing dice.

I would hate to be a beauty contest judge where there is only going to be one winner. Everyone's taste is a little different when it comes to what is prettiest or which one looks the nicest. We can definitely agree on certain aspects of beauty, but we have no ability to agree on how to select the prettiest diamond as that is quite subjective to each viewer. You can judge by committee, but that is not going to make all the right choices for everyone. It is best for each person to decide for themselves once they know they are in the right range of performance and beauty in a diamond. However, if the top range is too broad, then the consumer is left unaided and the unscrupulous will say all of them are the same. We know the drill already and we'd like to do better. There is no point in making an obvious mistake in bringing forward a so-called improvement that may be no improvement at all.
 

michaelgem

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I agree with David''s well spoken ideas repeated here:


"My own comment is that modeling is very useful to cutters as it provides them choices and recipes for cutting and re-cutting diamonds to perform better. There is a huge need for cutters to learn about these changes and what to do with rough.
However, when it comes to GRADING diamonds, it just seems better are more reasonable to measure the actual performance than to estimate it through a huge process of measuring lengths, angles, facet ratios, etc.

My thoughts are that both methods, direct measurement and calculation of performance are highly useful tools, but for different parts of the trade. I don''t think it is logical to always calculate the light performance if one can measure it. It is very proper to calculate POTENTIAL light performance for instructing cutters on how to work rough or to recut diamonds. The end result should be measured, not calculated..........


I think my logic is way more solid than my ability to argue scientific details or technicalities with PHD''s and optical experts. I am just a guy with a deep interest in what is going on and have a degree of involvement in this ongoing process. Our industry will benefit the most from developing the best products. I have seen so many half-baked products come and go. This time, I sure would like to see our business make the best choices and use solid science, not smoke and mirrors." David S. Atlas


I add the following from my post to Bruce Harding:


"We believe most aspects of optical performance or diamond beauty may be more accurately observed, (or predicted), and evaluated from stationary images of a diamond , (face-up and tilted), under a representation of typical illumination and viewing circumstances." Michael D. Cowing


Re: Michael:
. Thanks for compliments.
. It sounds like your last paragraph, highlighted, is a quote from something. If so, what? Bruce L. Harding

This is my wording of the concept that I have been promoting for 6 plus years beginning in print in my 2000 Journal article and, among other ideas, elaborated upon in the 2005 Journal article: "Describing diamond beauty - assessing the optical performance of a diamond". A four page digest version, which you would better appreciate for its brevity, appears in the latest NY Diamonds Magazine and Israel Diamonds Magazine.


I have found a number of people that promote or are sympathetic to this idea or concept. I believe we can adequately handle the objections that have been posed concerning ''direct assessment'' from diamond imaging. For example, I have made the camera lens adequately ''see'' what my asymmetrically placed eye sees in typical illumination (including the diamond''s fire).


I like direct assessment from images of diamonds under a representation of typical viewing and illumination circumstances, because it can clear away for the consumer the mystery, smoke and mirrors, and allows for clear and easy-to-understand explanations of what constitutes the best, (or do I dare say Ideal?), diamond cutting.


Michael Cowing


 

He Scores

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RE: i.e. do people consistently prefer the higher numbers on the devices? Are the bands established consistent with these reactions, or with some ostensibly more objective measurement, which we should then discount, if the objective measurements don’t conform to the pattern of human observation?

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You will not find an absolute when your assessing human behavior. My own feeling is that this is why GIA did not release the actual results of their own observation tests. Also, cut measurements are only one of perhaps 5 or 6 elements that relate to how a diamond "performs".

In my own research regarding physical observations of stones that underwent BrayScore anaylysis, approximately 56% of the trial could put three stones in their correct order of BrayScore scores from lowest to highest. However, 95% of them could put them in the correct order or alternate the top two stones which had only a 60 point difference out of 1000.

I feel that this is a similar error rate when equated to clarity grading of trades people missing a flawless versus a VV1 or a VV1 versus a VV2. Color grading has a higher error rate I believe.

Incidentally, when the stones were presented to the observer, they were presented in such a way that they could loupe them or view them with their naked eye. 82% louped them first to judge cut quality. 18% chose to view them with their naked eyes first. 100% eventually louped them.

As far as assessing repeatability of linear measurements from stone and from machine to machine, BrayScore anaylysis can be used as a tool to test the accuracy of different machines since the scoring analysis of the measurements is totally objective.

BrayScore judges a stone in a similar way that the trade looks at them and certainly the way that a cutter looks at them.

Bill Bray
Diamond Cutter
BrayScore.com
 

michaelgem

Shiny_Rock
Trade
Joined
Feb 26, 2003
Messages
379
For more than 6 years I have been saying that if you want to define a best or ideal cut you should first spell out with respect to what criteria your cut is ideal, and then you need to justify that claim.

Is it with respect to craftsmanship criteria such as perfection of polish, facet meet points, facet alignment, symmetry, facet angles and proportions? Before performance became the buzzword, most grading of diamond cut made judgments that fell within the craftsmanship category. A Bill Bray score of close to 1000 is an example, as is the old AGS 0 grading system.

Today and increasingly, the savvy consumer, like strmrdr, is looking for proof of the extent to which all the various factors of craftsmanship have or have not actually resulted in the most beautiful diamond in realistic illumination and viewing circumstances. This category of ''direct assessment'' of performance aspects of diamond beauty such as brilliance, fire and scintillation has gone mainstream with the GIA cut grade and the performance oriented changes to the AGS cut grade.

So is your cut ideal with respect to the performance attributes of diamond beauty- brilliance, fire, and sparkle? If so your customer may want to know in what way you are maximizing these attributes of diamond beauty. I doubt the savvy consumer will be satisfied with you measuring diamond performance and beauty up to a point and then saying beyond that it is a matter of taste.

I doubt there is much interest in a diamond said to be a fiery ideal and only good on brilliance, or one said to be a brilliant ideal that is so-so on fire.

I suspect to convince the consumer that their cut is best or ideal the jeweler will need to make the case that his diamond has the comparatively best combination of the three established performance attributes of beauty - brilliance, fire and sparkle. These attributes must be present in typical viewing and illumination circumstances, not just in the jewelry store. And the jeweler will need to back that case with clear and understandable evidence, not just numbers from an impressive piece of equipment.

I temper these beliefs with the acknowledgment that the savvy consumer being discussed is still a small although growing segment of the buying public most of who buy on emotion, price, brand identity or numbers from an impressive piece of equipment. Most of the large jewelry stores I know are too busy making money with the majority to bother going after this growing minority.

That is fine, because there are plenty of dedicated companies who are filling or moving to fill this small and growing market niche.

Michael D. Cowing


 
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