Brilliance Scope Question...

[sjr]

First off, sorry if this has been beaten to death and I just missed an old thread. I appreciate any links to them if possible- thanks!

From my brief experience with photospectrometers (what GOG says the B-scope is a version of) I thought the recordings are measured by either the absorbance or transmission/reflection of a substance that are calibrated from a constant (in my case, light was passed through solutions with water being the calibrated zero). The wavelengths being measured come from a 400-700 nm light source.

1. First question- What is the machine calibrated with- a mirror with 100 % wavelength return? Or is the machine calibrated to a database of previous stones or parameters? If the latter, are using different scales for different cuts portraying that b-scopes should only be used as a measure of relevance and not actual light return (otherwise the same scale should be used for all stones to remove any bias of how much is being returned- right?)


2. How does the machine differentiate between ''colored light'' and ''white light'' - when I assume the machine simply measures the magnitude or intesnity of each wavelength being returned? Or are ''clusters'' of light return measured and the ratio of differing wavelengths the determiner of white light (all wavelengths) or colored light (lets say less than 50 % of all wavelengths with equal intesity for hypothetical example)? And would not the overlap of white light return on colored light unfairly boost the actual amount of lets say blue light at 500 nm and give it too high a mark for fire?

I don''t have access to great stones where I live nor would I ever trust my own eyes with so little experience (I, instead, use you all Thus, I have to live by the numbers and get a great stone over the net- which I am most comfortable with. As such, I can''t thank pricescope members enough for your most beneficial information and willingness- and also giving me yet another excuse to sit at my computer whenever I can and do some more research

. I think my addiction is getting out of control- Thanks, SJR

 

[Rhino]

Hi sjr,

I''ll do my best to answer your questions based on my knowledge of the subject however I don''t lay claim to "knowing it all" but do have pretty extensive experience working with the equipment. I''ll forward this response and your questions to Gemex for clarification as well.

1. First question- What is the machine calibrated with- a mirror with 100 % wavelength return? Or is the machine calibrated to a database of previous stones or parameters?

The machine is calibrated with with a square and on the square is 4 different shades of contrast divied up from white, light gray, dark gray and black. It runs through the 5 primary light positions as it is calibrating and records large strings of numbers that it stores in its calibration files. It would be my educated guess that when it scans a diamond it compares the metrics/numbers of that diamond with the calibration standard. Now ... I do know that once a diamond is scanned the results are compared with their database in which thousands of other round brilliant cuts have been scanned, compared and saved. Everytime a Gemex user updates their software the most recent database results are included.

If the latter, are using different scales for different cuts portraying that b-scopes should only be used as a measure of relevance and not actual light return (otherwise the same scale should be used for all stones to remove any bias of how much is being returned- right?)

The approach Gemex has taken on this is to compare each shape within its own category instead of using a linear scale for all shapes. To my knowledge both GIA and AGS are also taking this approach as well. Having said that however any Gemex user can easily compare any shapes results to that of the round, thus incorporating the linear scale. I show this in some of my tutorials, particularly on super ideal cut squares comparing their results to both squares (their respective shape) and also to that of rounds. That is one of the beauties of the technology is we can compare results of any diamond to any scale we choose to. There are times clients do want to compare the results of a fancy they are considering to that of the round and we are happy to oblige.

2. How does the machine differentiate between ''colored light'' and ''white light''?

As direct light strikes a diamond the primary internal *flash* takes place on one of the pavilion facets and is then broken down into its spectral components. The initial *flash* is generally that of white light and the remaining light is that which is broken down into the various spectral colors. The B''scope analyzes and seperates where the white light transforms to colored, records the pixel count and reports the results. In our tutorial on the subject we show the actual seperations as the software allows us to distinctly *see* either only the white light being returned as opposed to the colored light and we have a chart explaining which facets are being illuminated at the given light positions. Here is one of the graphics for an example of a test stone and only in light position 2 for simplicity. The primary colored light being shown emanated from the facets in this position is that of blue. The technology also shows that the 2 most prominent colors being refracted within diamond overall is that of yellow and blue (although many other colors emanate from within).

Hope this helps.

 

[sjr]

Ha ha- thanks Rhino for the reply. I was going to email you this question as well but figured I would give your email box a rest for a moment.

I really need to get back to work, but.... I..... can''t help it.

1. I know you can run a stone at any setting to see how it fares on every scale- but my problem is --> if Gemex, GIA, and AGA are associating stones'' qualities based on the respective shapes (my comment on measure of relativity), should there not be an asterisk next to the terms brilliance, fire, and scintillation (in every setting)- since they are qualitative and not asbsolute terms across the board? I can thank Bonds and MLB for even putting * in my mind.

And it seems that categorizing (if this is what Gemex, GIA, and AGS are leaning towards) appears to be a bias towards the vendor/market and not the consumer?Take a vendor (nobody here on pricescope- of course!) who adds value to a stone based on a triple VH score, where in reality it is not. Of course the trained eye is the deciding factor on price setting; but here, the consumer would probably pay both a slight premium (understandable) for this b-scope technology (on top of the GIA/AGS report) and for the fact that certain shapes have their own scales to boost their own respective scores. I know I always have a choice, and if my comments border on offensive grounds- I will happily retract with apology.

2. So am I to interpret that the B-scope measures pixels from a ''digital picture'' and not really wavelengths of light that a spectrometer would? (otherwise in your picture, Rhino, there would not be any gaps in the ''only'' blue light where white light was removed--> as white light contains blue light!) That makes sense if so, but it all seems a little oversimplified. In all cases, I must add I probably won''t buy a stone without getting a b-scope report- ha!

I know B-scope is only one of many measures that can be used to identify a good stone, but I always get hopelessly caught up in irrelevant details so please bear with met--> It is just fun to discuss things in an environment where I have little grasp of things, Thanks, sjr

 

[strmrdr]

The separate scales is the biggest thing that removes the b-scope from a scientific instrument and makes it a sales and marketing tool.
It doesnt make it useless but it has to be considered from that angle.

 

[Spear]

style="WIDTH: 99%; HEIGHT: 128px">Date: 5/21/2005 10:20:16 PM
Author:sjr

2. How does the machine differentiate between ''colored light'' and ''white light'' - when I assume the machine simply measures the magnitude or intesnity of each wavelength being returned? Or are ''clusters'' of light return measured and the ratio of differing wavelengths the determiner of white light (all wavelengths) or colored light (lets say less than 50 % of all wavelengths with equal intesity for hypothetical example)? And would not the overlap of white light return on colored light unfairly boost the actual amount of lets say blue light at 500 nm and give it too high a mark for fire?

That it a good question.

What I would like to know is, Does the brilliance scope differentiate between internal brilliance and lustre?
IOW Does the brilliance scope display seperate readings for the 2 or one reading for both?

 

[Garry H (Cut Nut)]

A relevant excerpt from the IDCC document.
http://www.ideal-scope.com/newsletters_issue006.asp

Diamond Cut Grading System based on 3D model - A Strategy for Development
by Sergey Sivovolenko (OctoNus) and Yuri Shelementiev PhD (MSU Gemological Center), Moscow, Russia.
The words we use: We all agree that the Diamond Industry needs constant growth and development, but are some of the key marketing concepts we use still useful?
"A Diamond is Forever" does it lead to commoditization: "A Diamond is a Diamond"
We all say (including Labs) "the round brilliant is best"
"Ideal Cut" implies that everything else is less than "ideal"
The global consequences of using such concepts contribute to the commoditization of diamonds. If value adding decreases, there is an increasing risk of instability. We would like to propose a way to develop a solution for the cut part of this problem by designing a system that gives equal rights of cut evaluation for all cuts. We believe this would be a useful tool that will lead to effective diversification. Our discussion will also consider grading systems used in other industries. Three different cut grading approaches: 1) Parametrical; 2) Direct light measurements; 3) 3D diamond model.

Sergey and Yuri see that all cuts have a 'right' to be produced and compared to the round 'ideal cut'. Yet here we are discusing the 'right' to only be compared to other stones of the same shape / cut. Sometimes it takes 'new thinking' to make 'quantum leaps' (funny term that - quanta are actually very very tiny or non existant things).

 

[sjr]

Gary- I found your link to be rather interesting. Especially the comment by Sergey, "If value adding decreases, there is an increasing risk of instability" in relation to, "Now the general public attempts to use this technical and specialized language and knowledge. Is this appropriate for consumers?" by Tolkowsky.

I think it is inevitable that the consumer will become increasingly educated because of the internet. I join forums now for anything from a digicam to even an electric shaver simply and only to gain knowledge into what product is the best. These are things I am able to do in five minutes over a lunch period. I think I am not in the minority with such research as most all of my peers (mid 20s) do the same when purchasing almost everything.

My question is ,then, if there will be a trend of more educated consumers- could this fact co-exist and not clash with ''value adding''? I feel my biggest focus now is slicing through the creative marketing to get to the real product (related to my qualm with b-scopes). Perhaps you could expand the view of your colleagues that there would be increasing instability and how this would truly hurt the overall market? Or is he saying that these ideas of ''value adding'' should instead be replaced with a more uniform grading (to start) that will tailor to the educated consumer? Sorry that I am asking question based on excerpts from a whole discussion--> and might be totally out of context not to mention a year old...

The longer I wait to get my first stone- my b-scope report might only have a few quantas of photons. So it goes- ha! sjr

 

[Garry H (Cut Nut)]

The topic discussed a bit at the IDCC was commoditization.
Wine rankings and hotel ratings have not done that. And it is interesting that Marten De Witte from Hearts on Fire gave a wonderful presentation which is summarized there too.
There exists a place for all types of products. What we want though is a cut grading system that makes generation of new cuts easy and the cuts should be good - not like so many of the branded rubbish that came on the market over the last 3 years. Now if you want a generic round or princess that you can buy at a steal from a low margin operator that is cool. Someone else might want a Tiffany ring - that''s cool too (Although they will soon be forced to raise their cut standards and keep up with the improvements that have been occurring).
But imaging the prestige of owning a one off or limited edition ''bueaty'' as Gabi would say?

 

[Garry H (Cut Nut)]

I should add that a # of the branded offered by some of the cut junkies that hang around here I would exclude from my comments above.
And where there is more variables - it is possible for many of these fancy cuts to have different ideal-scope appearances and personalities, yet still be well cut stones - just as there is aa much wider range of noce round stones that we will be seeing soon from the new grading standards.

 

[valeria101]

Date: 5/22/2005 10:17:26 PM
Author: Garry H (Cut Nut)

What we want though is a cut grading system that makes generation of new cuts easy and the cuts should be good ...

Between the current GIA and AGS systems... is any at least more amenable to being extended over new shapes that were not taken into account into building the standard ?

To my understanding, GIA''s has that property in alatent form while AGS''s approach does not.

I would venture to say that the cut grading system you describe in that quote above, could only come from a cutter''s group - be it via the current labs (thought as market structure) or (allot easier) aside them. Is there anything out there to support such prediction ? Just curious.

 

[Rhino]

Hi sjr,

Thanks for the quick response. I''ll respond in the usual fashion. If there is any point I am not addressing that you''d like further explanation on let me know and I''ll do what I can to delve deeper if you like.

Date: 5/22/2005 4:17:50 PM
Author: sjr
Ha ha- thanks Rhino for the reply. I was going to email you this question as well but figured I would give your email box a rest for a moment.

I really need to get back to work, but.... I..... can''t help it.

LOL... I know all too well what it''s like to have the "info bug". It drives me as well.

1. I know you can run a stone at any setting to see how it fares on every scale- but my problem is --> if Gemex, GIA, and AGA are associating stones'' qualities based on the respective shapes (my comment on measure of relativity), should there not be an asterisk next to the terms brilliance, fire, and scintillation (in every setting)- since they are qualitative and not asbsolute terms across the board? I can thank Bonds and MLB for even putting * in my mind.

Perhaps they should to let consumers know that the scale is not linear. We publish this information for all to see on our website and let consumers know of the options they have with regards to the technology. If they prefer to see their shape on a linear scale we''ll do it. I can understand however why Gemex & AGS would want to keep shapes within their respective category because it lets consumers know how any particular diamonds fares amongst others within the same shape. For example if a person is interested in princess cuts and enjoys the appearance of a princess cut over a round, why would that person give a hoot how their princess cuts performs in relation to a round? They want to know how any princess cut they are considering fares against other princess cuts, not rounds since they don''t even want a round to begin with. This is the logic behind the qualitative analysis and while I do enjoy seeing how various shapes compare on a linear scale, I can at the same time understand the logic behind this principal. People have a natural tendency to assume the worst intentions (qualitative for marketing purposes) but there are real reasons for this that have nothing to do with marketing. I''m still a believer in innocent until proven guilty.

And it seems that categorizing (if this is what Gemex, GIA, and AGS are leaning towards) appears to be a bias towards the vendor/market and not the consumer?Take a vendor (nobody here on pricescope- of course!) who adds value to a stone based on a triple VH score, where in reality it is not. Of course the trained eye is the deciding factor on price setting; but here, the consumer would probably pay both a slight premium (understandable) for this b-scope technology (on top of the GIA/AGS report) and for the fact that certain shapes have their own scales to boost their own respective scores. I know I always have a choice, and if my comments border on offensive grounds- I will happily retract with apology.

I realize that categorizing appears to be biased towards the vendor/market but as I brought up above ... there are consumers who are interested in a respective shape (or shape category) who could give a hoot how it compares to a round ... or a marquise etc. Most consumers are generally concerned with how a particular diamond fares against other comparable stones which are not necessarily the same shape. Even if you prefer a linear comparison can you at least empathize the point? And ... your questions are not, in the least offensive. Your questions are welcome sjr.

2. So am I to interpret that the B-scope measures pixels from a ''digital picture'' and not really wavelengths of light that a spectrometer would? (otherwise in your picture, Rhino, there would not be any gaps in the ''only'' blue light where white light was removed--> as white light contains blue light!) That makes sense if so, but it all seems a little oversimplified. In all cases, I must add I probably won''t buy a stone without getting a b-scope report- ha!

If it seems a little oversimplified its because I try to explain things in a very simple manner. The 2nd graphic in my post above was not ''only'' blue light. My comment was that it consisted ''primarily'' of blue light. Yes, blue is contained in white light but so are all the other colors (ROYGBIV). It when that white light is broken down into its individual spectral colors that the b''scope records and captures. There is an option in the software which will show us a breakdown of the colors blue, yellow, red and green and the quantity of those colors it reports back for each stone as well.

I know B-scope is only one of many measures that can be used to identify a good stone, but I always get hopelessly caught up in irrelevant details so please bear with met--> It is just fun to discuss things in an environment where I have little grasp of things, Thanks, sjr

Hey... I really do enjoy discussing it too. As I''ve said in many former posts, the most important element about the technology *to me* is that it correllates to human eye observation. As it is with any other technology (HCA, Isee2, IdealScope/FireScope/LightScope, MSU ... haha... and yes even the new Imagem!) each of these have the strengths, weakness'' and limitations. What is important is that the consumer consulting the results any of these tools understand these elements as they review the data. And as I will always advocate ... the more data the better. I''d rather have it than not. What has been of keen interest to me over the 5 years we''ve been using it is that as new studies are released by other research gemologist within the trade who do not use the B''scope, NEVER have I see a study released that contradicted the information it reports and this includes AGS most recent release of "ideal princess cuts" as demonstrated in another thread. The more I learn the more I appreciate the technology.

Peace,

 

[Rhino]

Date: 5/22/2005 5:05:22 PM
Author: strmrdr
The separate scales is the biggest thing that removes the b-scope from a scientific instrument and makes it a sales and marketing tool.
It doesnt make it useless but it has to be considered from that angle.

Then AGS system for princess cuts should be tossed out the window based on this same logic.

 

[Rhino]

Date: 5/22/2005 7:54:59 PM
Author: Spear

style="WIDTH: 99%; HEIGHT: 128px">Date: 5/21/2005 10:20:16 PM
Author:sjr

2. How does the machine differentiate between ''colored light'' and ''white light'' - when I assume the machine simply measures the magnitude or intesnity of each wavelength being returned? Or are ''clusters'' of light return measured and the ratio of differing wavelengths the determiner of white light (all wavelengths) or colored light (lets say less than 50 % of all wavelengths with equal intesity for hypothetical example)? And would not the overlap of white light return on colored light unfairly boost the actual amount of lets say blue light at 500 nm and give it too high a mark for fire?

That it a good question.

What I would like to know is, Does the brilliance scope differentiate between internal brilliance and lustre?
IOW Does the brilliance scope display seperate readings for the 2 or one reading for both?

NOW THIS is a very good question Spear and I am glad you raised it. Of all of the tools we work with I believe there is only 1 that takes into account external reflections as well as internal and that would be the MSU software. Unfortunately, while the software does give a metric for light return (both stereo and mono) it does not accurately report the metric of *brightness* (ie. contrast) nor does it yet have metrics for fire or scintillation. I believe these will be included in the next release of the software (both DiamCalc and Gem Advisor) as I''ve emailed Andrey and Serg concerning these issues. I am confident the next release will be jam packed with great features. Currently, B''scope, Isee2, Red reflectors, & HCA do not account for external reflections or lustre.

 

[Spear]

Date: 5/23/2005 3:27:23 PM
Author: Rhino

NOW THIS is a very good question Spear and I am glad you raised it. Of all of the tools we work with I believe there is only 1 that takes into account external reflections as well as internal and that would be the MSU software. Unfortunately, while the software does give a metric for light return (both stereo and mono) it does not accurately report the metric of *brightness* (ie. contrast) nor does it yet have metrics for fire or scintillation. I believe these will be included in the next release of the software (both DiamCalc and Gem Advisor) as I''ve emailed Andrey and Serg concerning these issues. I am confident the next release will be jam packed with great features. Currently, B''scope, Isee2, Red reflectors, & HCA do not account for external reflections or lustre.

The reason why I ask,
Although I don''t yet understand the componants of lustre.
IOW what makes one stone display more lustre then another.

I am wondering if a well proportioned stone that displays a small amount of external brilliance would score equally as high on the brilliance scope then a poor proportioned stone that displays a large amount of external brilliance.
Hope that makes sence!

 

[strmrdr]

Date: 5/23/2005 3:18:16 PM
Author: Rhino

Date: 5/22/2005 5:05:22 PM

Author: strmrdr

The separate scales is the biggest thing that removes the b-scope from a scientific instrument and makes it a sales and marketing tool.

It doesnt make it useless but it has to be considered from that angle.

Then AGS system for princess cuts should be tossed out the window based on this same logic.

*yawn* apples and oranges
Since you know my views on the scale issue very well I dont see the need to argue bout it :}

 

[strmrdr]

Date: 5/23/2005 3:27:23 PM
Author: Rhino

Date: 5/22/2005 7:54:59 PM

Author: Spear

style="WIDTH: 99%; HEIGHT: 128px">Date: 5/21/2005 10:20:16 PM

Author:sjr


2. How does the machine differentiate between ''colored light'' and ''white light'' - when I assume the machine simply measures the magnitude or intesnity of each wavelength being returned? Or are ''clusters'' of light return measured and the ratio of differing wavelengths the determiner of white light (all wavelengths) or colored light (lets say less than 50 % of all wavelengths with equal intesity for hypothetical example)? And would not the overlap of white light return on colored light unfairly boost the actual amount of lets say blue light at 500 nm and give it too high a mark for fire?

That it a good question.


What I would like to know is, Does the brilliance scope differentiate between internal brilliance and lustre?

IOW Does the brilliance scope display seperate readings for the 2 or one reading for both?

NOW THIS is a very good question Spear and I am glad you raised it. Of all of the tools we work with I believe there is only 1 that takes into account external reflections as well as internal and that would be the MSU software. Unfortunately, while the software does give a metric for light return (both stereo and mono) it does not accurately report the metric of *brightness* (ie. contrast) nor does it yet have metrics for fire or scintillation. I believe these will be included in the next release of the software (both DiamCalc and Gem Advisor) as I''ve emailed Andrey and Serg concerning these issues. I am confident the next release will be jam packed with great features. Currently, B''scope, Isee2, Red reflectors, & HCA do not account for external reflections or lustre.

Is it that big a deal in direct light envirements?
If the pavilian reflectors are doing the proper job external reflection return will be blown away by the external-internal-external light return.
In indirect light id see it being more of an issue.

 

[sjr]

People have a natural tendency to assume the worst intentions--- hmmmm....I seem to have heard that before and she stands 5''6" with brown hair and is looking to put some massive geological creation on her finger

As both Rhino and Gary point out, there are of course people from all sorts, and I am not disputing this. I am simply pointing out how a new trend of minutely-educated-virgin stone purchasers as myself would perhaps get a slighty odd look of incompatability from a Tiffany''s worker when I whip out my ideal scope, ask for a b-scope report and a computer to plug the numbers which they ''guarantee'' in the HCA. They just don''t seem to mend well--> probably to my other''s dismay in that she will probably not get that blue box.

Back to my tangential concern: Rhino, perhaps we are just not communicating our thoughts on the same page. You say "It [is] when that white light is broken down into its individual spectral colors that the b''scope records and captures" Well, this was my original question which I can''t seem to understand from your picture. If white light is broken down into all its color components (whatever of ROYGBIV one chooses), why would there be a black spot ANYWHERE where white light once was as it certainly contains every ROYGBIV color there whithin it? Does this picture somewhat convey what I am talking about?

Thanks all for the interesting reponses! sjr

 

[Garry H (Cut Nut)]

Rhino wrote "Currently, B''scope, Isee2, Red reflectors, & HCA do not account for external reflections or lustre."

I think all mentioned cut grade systems do account for exterior reflections except GIA originally removed them in their brilliance study from 1998.root>

 

[JohnQuixote]

Note: I have reserved comment as I did not want to revisit prior BS issues from many threads. Jonathan and I have a 'no-fly zone' understanding with Brilliancescope. When a consumer thread is not specifically about BS, and sometimes when it is, we avoid hijacking it with opinion-dodgeball.

However, this thread has posed some new, intelligent, questions. So... here I go (you can hear Rhino gnashing his teeth all the way from NY!)

Date: 5/23/2005 3:46:34 PM
Author: Spear

The reason why I ask,
Although I don't yet understand the componants of lustre.
IOW what makes one stone display more lustre then another.

I am wondering if a well proportioned stone that displays a small amount of external brilliance would score equally as high on the brilliance scope then a poor proportioned stone that displays a large amount of external brilliance.
Hope that makes sence!

Spear,

Diamond is practically transparent. The lustre of a well made diamond is described as adamantine. It is distinctive. This factor was considered long before Brilliancescope. The polish grade represents the quality of lustre. Well made diamonds typically have polish that is vg or above. Those with substandard polish will be identified as so on the grading report.

Between 2 diamonds with vg polish (or better) luster – and external reflection – are non-factors in typical light conditions:

"In a diamond, the amount of light reflected from the surface is much smaller than that penetrating into the stone; moreover, a diamond is practically perfectly transparent, so that all the light that passes into the stone has to pass out again. This is why lustre may be ignored in the working out of the correct shape for a diamond, and why any variation in the amount of light reflected from the exposed surface due to a change in that surface may be considered as negligible in the calculations. The brilliancy or, as it is sometimes termed, the " fire " or the " life " of a gem thus depends entirely upon the play of light in the gem, upon the path of rays of light in the gem. If a gem is so cut or designed that every ray of light passing into it follows the best path possible for producing pleasing effects upon the eye, then the gem is perfectly cut. The whole art of the lapidary consists in proportioning his stone and disposing his facets so as to ensure this result." - Marcel Tolkowsky

I'm sure T-dawg did not envision technology like the Brilliancescope that bombards diamond with artificial light and counts pixels to acquire a score. This kind of assessment has been questioned since it was developed. It’s treating the diamond to conditions it will never see in nature. It is why the science community has leaned toward Ideal-scope & ASET assessment devices that can rely on natural light conditions, and not atypical/uber-lighting. Even so, we are still working to arrive at a natural standard for reflector assessment.

I’ve never understood the BS attempt to separate white light and colored light. Why try to quantify in numbers what the eyes will always see together? White and colored light work in harmony to create the ‘life’ of a diamond. Even if it this measure was accurate it seems irrelevant to the average consumer. To me it’s like trying to sell a Krispy Kreme by mechanically separating smells in an attempt to tell you how much milk versus how much flour is in it.

The thing I do enjoy about BS is looking at the photos. In the hands of someone skilled this machine can tell some of the story about a diamond through analysis of photos and light behavior - but I worry about consumers who rely on BS scores to guide them, especially in a sales/marketing capacity where the operator or interpreter has limited experience or knowledge.

I have the highest respect for Jon’s experience on this device and am confident he and Bill are the best spokesmen available for it. I’m looking forward to continued discussion.

 

[Garry H (Cut Nut)]

Here is a litttle brain teazer.

Why bother centering the diamond?

 

[valeria101]

Date: 5/23/2005 11:15:49 PM
Author: Garry H (Cut Nut)
Here is a litttle brain teazer.

Why bother centering the diamond?

Because brilliance and optical symmetry got mixed up in the public image of cut quality, perhaps ?

That centered image taken long the axis of symmetry may be thought to "average out" the views taken from all positions on a above the girdle section. The math does not have to hold to back up the intuition that the table-down image is somehow "representative" of the diamond.

Even if the center image is a valid "average" in some technical way, it sounds impractical to favor one static view over all others because its chance to pass in front the eye of the observer is no better than that of any other angle from a large neighbourhood.

--------------------------------------------------------------------------------------------------------------------------------

How confusing is that ?

In short: I don't think there is a reason to consider the centered image as representative.

So my direct answer to the question is: "Don't bother"

Now, it is obvious that many serious people do bother and it is not very hard to find a reason for each context. The H&A cut grading method clearly needs it. The vertical axis of symmetry is the reference for the design of the RBC cut... By construction, that top-down projection might have desirable properties for constructing light return metrics... And there must be many other reasons to take that view for reference from a purely technical view.

Once diamonds are out of the lab, the top down view is no longer privileged - in my opinion. The diamonds will not be seen straight top-down any more often than from a 5 or 10 or 30 degrees tilt from the vertical. Also, those diamonds will rarely be seen in a static position - jewels glitter with movement and viewers are not statues. Taking the centered image only to give a quality mark to the stone, assumes that just that one static position out of a fairly wide range of viewing angles contributes dramatically more to the perceived appearance of a stone.

 

[Garry H (Cut Nut)]

Ana, I think you said that people rarely look perfectly face on to a diamond (except maybe when they are buying it?).

Another thought is that the lights are not lined up symmetrically.

But what i was getting at - you also picked up on - the Bscope prefers symmetric diamonds, but the non symmetric lighting world could be better replicated by deliberately putting stones off center

 

[valeria101]

Date: 5/25/2005 1:42:19 AM
Author: Garry H (Cut Nut)

But what i was getting at - you also picked up on - the Bscope prefers symmetric diamonds, but the non symmetric lighting world could be better replicated by deliberately putting stones off center

Garry, why is it thought that devices used to classify diamonds'' optics should replicate natural viewing conditions ? This is rather unique among measuring devices, if my memory serves...

It is crystal clear why the metrics derived from measurements should match viewer''s expectations, but this is a different matter concerning interpretation, not measurememt.

 

[JohnQuixote]

Date: 5/25/2005 3:48:10 AM
Author: valeria101

Garry, why is it thought that devices used to classify diamonds' optics should replicate natural viewing conditions ? This is rather unique among measuring devices, if my memory serves...

It is crystal clear why the metrics derived from measurements should match viewer's expectations, but this is a different matter concerning interpretation, not measurememt.

Ana, can you elaborate?

 

[Rhino]

Sorry guys. I was swamped yesterday and barely finished my emails. Just gotta do a few errands this morning and I''ll catchup. Haha John!!! Don''t sweat it about the hijacking thing. I''m always ready for good discussion.

 

[valeria101]

Date: 5/25/2005 9:31:18 AM
Author: JohnQuixote

Date: 5/25/2005 3:48:10 AM
Author: valeria101

Garry, why is it thought that devices used to classify diamonds'' optics should replicate natural viewing conditions ?
The metrics derived from measurements should match viewer''s expectations, but this is a different matter concerning interpretation, not measurememt.

Ana, can you elaborate?

Sure, but the stuff might be terribly boring.

And it may be that my interpretation of Pricescope chatter is totally skewed.

Starting from the news about GIA and AGS cut studies, I have been trying to understand what is the rationale behind cut grading methodology. Perhaps due to patchy information, it is not very clear what cut grading is: measure optics (which sounds like plain use of technology) or measure human preferences (which is somewhat more debatable). Either can be done, of course, but it seems odd that some metrics are expected to do both at once because the methodology of these procedures - from experimental and non-experimental science - doesn''t mix all that well.

The confusion started from this puzzle: why are the lighting conditions used by various measuring devices & procedures criticized for lack of realism instead of their results being criticized ?
For example, statements like the following make the object of my inquiry. These did cross the forum by and large:

- "the brilliance scope measures performance under direct lighting conditions"

- "ISee2 scores diamonds under diffuse lighting"

- "small variation of handling and lighting skews IdealScope results"

- when Gemappraisers introduced DiaGem its lighting conditions were immediately questioned...

This sort of thing.

Making measuring conditions more realistic does not seem to contribute to the task at all because those conditions do not address human senses but some device that has different operational requirements. That the measurements were taken in visually pleasing conditions does not support the claim that the result mimics visual perception... Or does it ?

To make a cheap analogy: no one seems to question the results of a room thermometer just because it does not complain of cold. The thing does its job producing a standardized metric that relates loosely to personal perceptions. Has anyone found one that reads "freezing", "cold" and "fuzzy" instead of Celsius/Fahrenheit ? Why do I need to read "brilliance" and "scintillation" on ''scope''s scale then ?

Unless ''scopes are not supposed to measure a definite technical property like the lowly thermometer, but subjective human preferences. And that''s quite an ambitious task that may not be welcome by any of the engineers I know.

In other words, questioning biasness of measurement conditions seems unusual if what is measured there are physical properties (say, optical effects). As far as I understand, the precision of the result does not depend on how well the measuring device mimics traditional appreciation of diamonds, but on the technical precision of reading some physical property.

Now, if measurement precision is desirable, why choose hard to measure, potentially subjective metrics like color (see the question about how the Bscope tells colored light from white) or symmetry (the Isee2 does that) ?

Oh well, please feel free to take this as an example of argumentative wordiness

despite my best efforts to avoid just that ...

 

[Rhino]

Just catching up on some reading here after seeing Carrie take it home! Dayum and I thought Bo was going to take it although I really didn''t care who won. Ok... back on topic.

Date: 5/22/2005 8:12:50 PM
Author: Garry H (Cut Nut)

Sergey and Yuri see that all cuts have a ''right'' to be produced and compared to the round ''ideal cut''. Yet here we are discusing the ''right'' to only be compared to other stones of the same shape / cut. Sometimes it takes ''new thinking'' to make ''quantum leaps'' (funny term that - quanta are actually very very tiny or non existant things).

LOL... (about quanta).

Gary I am all for optical grading on a linear scale. Getting the labs to agree however is akin to pulling teeth. What I''d like to see is actually 2 comparisons. One comparison being the diamond in question compared to other comparable shapes (and I''m not saying all squares either, just princess with princess, radiant with radiant, etc.) THEN if the consumer is interested a comparison of whatever shape they are considering next to that of the diamond that demonstrates the highest optical properties. Currently that does happen to be certain ideal round brilliants. In 6 months or a year... who knows?

 

[Rhino]

Date: 5/23/2005 3:46:34 PM
Author: Spear

Date: 5/23/2005 3:27:23 PM
Author: Rhino

NOW THIS is a very good question Spear and I am glad you raised it. Of all of the tools we work with I believe there is only 1 that takes into account external reflections as well as internal and that would be the MSU software. Unfortunately, while the software does give a metric for light return (both stereo and mono) it does not accurately report the metric of *brightness* (ie. contrast) nor does it yet have metrics for fire or scintillation. I believe these will be included in the next release of the software (both DiamCalc and Gem Advisor) as I''ve emailed Andrey and Serg concerning these issues. I am confident the next release will be jam packed with great features. Currently, B''scope, Isee2, Red reflectors, & HCA do not account for external reflections or lustre.

The reason why I ask,
Although I don''t yet understand the componants of lustre.
IOW what makes one stone display more lustre then another.

I am wondering if a well proportioned stone that displays a small amount of external brilliance would score equally as high on the brilliance scope then a poor proportioned stone that displays a large amount of external brilliance.
Hope that makes sence!

Hi Spear,

Sorry for the delay in my response. Past 2 days have been a little hectic. In answer to your question (which btw makes total sense), if a poor proportioned stone that displays a large amount of external brilliance is placed in the BrillianceScope it will not receive great results. Lustre is directly affected by the quality of polish and the high sheen which is the result. The BrillianceScope is a device that does not analyze the component of lustre and the graphics it depicts are those of internal reflections. Lustre and the quality of polish are best observed and graded under the microscope.

 

[Garry H (Cut Nut)]

Ana here is a quick answer

a cold temperature, say 0C or 32F - is mild with no wind and chilly in a gale.
that temperature is colder in Fall / Autum and warmer in winter because we are not used to it in Autum.

So we need more than one measure, and things get more and more complex

 

[Rhino]

Date: 5/23/2005 4:37:19 PM
Author: sjr
People have a natural tendency to assume the worst intentions--- hmmmm....I seem to have heard that before and she stands 5''6'' with brown hair and is looking to put some massive geological creation on her finger

As both Rhino and Gary point out, there are of course people from all sorts, and I am not disputing this. I am simply pointing out how a new trend of minutely-educated-virgin stone purchasers as myself would perhaps get a slighty odd look of incompatability from a Tiffany''s worker when I whip out my ideal scope, ask for a b-scope report and a computer to plug the numbers which they ''guarantee'' in the HCA. They just don''t seem to mend well--> probably to my other''s dismay in that she will probably not get that blue box.

Back to my tangential concern: Rhino, perhaps we are just not communicating our thoughts on the same page. You say ''It [is] when that white light is broken down into its individual spectral colors that the b''scope records and captures'' Well, this was my original question which I can''t seem to understand from your picture. If white light is broken down into all its color components (whatever of ROYGBIV one chooses), why would there be a black spot ANYWHERE where white light once was as it certainly contains every ROYGBIV color there whithin it? Does this picture somewhat convey what I am talking about?

Thanks all for the interesting reponses! sjr

HI sjr,

Please forgive my delay. Ok... if I''m understanding your question correctly, you''re asking ... "Why would there be a black spot ANYWHERE where white light once was....? And you highlighted the specific points in the graphics showing this.

The reason you see that gaping hole in image #2 (colored light only) is because the B''scope is seperating and removing strictly white light (yes, which consists of all of ROYGBIV) in graphic #2. So to put it in other words ... whenever the B''scope sees all of ROYGBIV (or white to keep it simple) it seperates that from any other color it sees. The reason is because when we observe white light as humans we do not see the individual colors ... we only see *white*. When other colors are removed then we start to observe to a greater degree the individual colors of the spectrum. This is the phenomena of dispersion. So when all of ROYGBIV is present the Bscope says hey ... that''s white! Let''s seperate it from the other colors as they are broken down into the spectrums. The 2 most prominent colors that light is broken down into within diamond happens to be yellow and blue. Why? At the current time I don''t know the answer to this question. Interestingly as I was learning these things from using the B''scope I had read a post of Garry''s (this is going back a few years ago) and he had stated that the 2 most prominent colors refracted within diamond were yellow nad blue also. I never commented but just took note that that was exactly what the B''scpe was showing from its data as well. Even breaking it down into percentages. Neat stuff. Hope that helped answer your question.

Kind regards,