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Which cert captures the most information on cut?

Discussion in 'RockyTalky' started by bluelotus, Oct 19, 2015.

  1. bluelotus
    Shiny_Rock

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    by bluelotus » Oct 19, 2015
    Hello all,
    If my goal were to document all angles and proportions data on a diamond is there a certification available that would cover that? Or, would I have to have a Sarin scan to capture all information? Do AGS certs offer scans as part of the assessment?
     
    


    


  2. bluelotus
    Shiny_Rock

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    by bluelotus » Nov 4, 2015
    Since I have received no responses let me rephrase my question:
    What is the best way to document the specific proportion data on a vintage diamond?
    My goal would be to be as accurate as possible. I understand that GIA certs round the averages so I would want to avoid that. My goal is twofold: to document the specifics of my stone for insurance, and to satisfy my geeky desire to understand the specific optics of my stone.
     
  3. chrono
    Super_Ideal_Rock

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    by chrono » Nov 4, 2015
    A Sarin scan will be required if you want that much information. I don't think any lab report provides as much information at this point in time.
     
  4. bluelotus
    Shiny_Rock

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    by bluelotus » Nov 4, 2015
    How does one go about getting a Sarin scan?
     
    


    


  5. chrono
    Super_Ideal_Rock

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    by chrono » Nov 4, 2015
    I've always had the vendor who sold the diamond to me provide it. Not all vendors have access to a Sarin scanner though.
     
  6. kenny
    Super_Ideal_Rock

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    by kenny » Nov 4, 2015
    I've read pros here state that AGS's cut grading system is far superior to GIA's.

    I think it's got something to do with actually measuring what the diamond does with light instead of measuring, averaging, and rounding angles like GIA does.

    Pros, please clarify/correct if needed. :oops:
     
  7. Rhino
    Ideal_Rock
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    by Rhino » Nov 4, 2015
    Actually a Helium Report is 2nd to none when it comes to actual angles, percentages, painting, digging, girdle graph, etc.

    GIA reports round too much.
    AGS reports, while more accurate to the actual angles and percentages still only provide averages and excludes upper half data.
    Sarin reports ... depends on the report generated. Sarin has the ability to generate some very detailed reports but most that you see online are reports only giving the averages.
    Helium reports show everything from every individual angle/percentage of each facet/facet set as well as azimuth deviations, degrees of painting/digging, ie. soup to nuts. The Helium Reports offer two options too. The scaled down version is the "Illustrated Report" while the more comprehensive version is their "Full Report" which is multiple pages.

    What you are referring to Ken is AGS PGS (Performance Grading Software) or ray tracing software. AGS utilizes two primary tools in their analysis. Most here know about the ASET but the PGS really takes it to another level as it takes a generated 3d file of the actual diamond (generated with either a Helium Scanner or Sarin's HD scanner) and examines the diamond with both 30 and 40 degree obscuration (head/body obstruction) as well as rotating the diamond and examining it's performance in dynamic movement as opposed to a single static image. A great tool.

    Kind regards,
    Rhino
     
  8. Texas Leaguer
    Ideal_Rock
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    by Texas Leaguer » Nov 4, 2015
    Great info Rhino.

    It sounds like the OP is more interested in the actual geometry of the diamond as opposed to grading. Therefore lab reports, even from AGS, are not the solution. Even though AGS light performance grading takes into account the entire geometry of the given diamond, and although it ray traces an accurate 3D scan, the document does not report the measurements in fully detailed form.

    Bluelotus- look for a local appraiser who has a Sarin or Helium machine that can run a scan and provide you with the full report. If there is nobody with that capability near you, there are top expert appraisers that frequent this forum that could provide that service.
     
  9. kenny
    Super_Ideal_Rock

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    by kenny » Nov 4, 2015
    Thanks Rhino and Bryan! :appl:

    In summary, can I say a round with AGS's top cut grade of 0 (Ideal) is more sure to be top cut than a GIA Excellent?
     
  10. sharonyanddave
    Rough_Rock

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    by sharonyanddave » Nov 4, 2015
    Since when? I would not call a snapshot at 15 degrees dynamic. The sum of the datasets of ASET30 and ASET40 at (-15 +15 and faceup) does not equal dynamic movement(like an ASET video) wouldn't you agree?

    It would be 'equavalent' if they summed many snapshots at say 0.1 degree increments but they do not as they use the approximation that a snapshot at 15 degrees is a 'good' indication of performance upon tilting.
     
    


    


  11. Texas Leaguer
    Ideal_Rock
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    by Texas Leaguer » Nov 5, 2015
    One of the many challenges AGSL had in developing their ray tracing system was one of computing power, both in the lab and in the commercial grading software that would be deployed out in the real world. The time it takes to make all the calculations presented some barriers to practicality. It is likely that an assessment was made that adding hundreds maybe many thousands of additional calculations for a full range of tilt positions would add greatly to the processing load without delivering a lot of additional value.

    It is important that the snapshots of tilt were incorporated into the grading system. This ensures that a diamond receiving an ideal grade not only performs well on-axis but at a significant range of tilt as well.
     
  12. sharonyanddave
    Rough_Rock

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    by sharonyanddave » Nov 5, 2015
    In the original research paper it was expressed that the largest number of scintillation events in the MRB were shown to occur between faceup and forward 15 degrees of tilt and this is a far more significant factor than a simple lack of "computing power".

    If AGSL want to incorporate larger datasets into AGS-PGS they can. However now they face a similar problem to GIA, they have 'loyal' customers (dealers and cutters) and history, and making any changes to their cut grading metrics might alienate their clientèle especially if/when any currently submitted designs no longer fit the 'theoretical optimal' criteria for receiving AGS 0000.

    Well if it doesn't deliver a lot of additional value than dealers who use their grading reports as marketing tools shouldn't claim the system does something(like analysis in dynamic motion) when it doesn't.

    That is a highly subjective, and poorly defended part of the secretive and proprietary AGSL grading system, a tilt of precisely 15 degrees is quite arbitrary in my mind and while it may be important for the modern round brilliant that approximation falls apart for other cuts. Intuitively I do not see a viewer tilting their diamond precisely 15 degrees but I could visualize the viewer tilting their diamond in all directions slowly up to 15 degrees.
     
  13. Texas Leaguer
    Ideal_Rock
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    by Texas Leaguer » Nov 5, 2015
    Very astute comments. I don't necessarily agree with all of them but you are clearly very knowledgeable. Are you in the trade?
    If so, by forum policy you need a trade badge. Contact admins and they will fix you up.

    Meanwhile, welcome to pricescope!
     
  14. sharonyanddave
    Rough_Rock

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    by sharonyanddave » Nov 5, 2015
    I am an academic not a diamond dealer, I have read and discussed Dr. Sassian's work in Optical Science, do I get a trade badge for that?
    You seem to make assumptions and speak on behalf of the AGSL lab do you work with them?

    Thanks.
     
  15. gm89uk
    Brilliant_Rock

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    by gm89uk » Nov 5, 2015
    Are all AGS 000 certificates equal? Some seem to be the platinum report which include the virtual ASET and some seem to just state that light performance is 0. Do all diamonds that acquire AGS 000 go through ray tracing?
     
    


    


  16. bluelotus
    Shiny_Rock

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    by bluelotus » Nov 6, 2015
    This thread has taken a direction that I had not anticipated but thank you Rhino and Bryan for your comments. As an owner of a transitional/early round brilliant diamond I am interested in understanding the stone's optical idiosyncrasies. I suspect that other old cut lovers would desire the same. Perhaps a trip up to Long Island is in order. . .
     
  17. Texas Leaguer
    Ideal_Rock
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    by Texas Leaguer » Nov 6, 2015
    Not all AGS0 certificates are the same. Not all go through the ray tracing protocol. The Platinum Cert includes the ASET light map (s). If there is a "light performance" grade on the report, it has been ray traced whether or not it contains a light map. Reports dated before 2005 are not light performance based.
     
  18. Texas Leaguer
    Ideal_Rock
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    by Texas Leaguer » Nov 6, 2015
    I don't think you need a trade badge as an academic. The the main point of the badge I believe is to indicate to consumers reading the forum something about your experience within the industry. That can also be an indication to consumers if you may have a bias in one way or another.

    I do not work for AGSL. I do work for an AGS member company and as such we are aligned with their mission. Our company stocks a large inventory of precision cut diamonds and have them graded at AGSL. I have therefore become pretty familiar with the lab over the years and I try to contribute my understandings when relevant to discussions on this forum.
     
  19. Rhino
    Ideal_Rock
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    by Rhino » Nov 6, 2015
    Thanks Bryan, thanks Ken. :wavey:

    That's a safe statement Ken albeit both labs do have differing criteria which constitute their top grades. We've been seeing a number of diamonds in the recent past that take a hit in weight ratio in the AGS system but are still GIA xxx too and without the diamond cut deep either. We saw one recently that took this hit with a 61.9% depth.

    All the best,
    Rhino
     
  20. Rhino
    Ideal_Rock
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    by Rhino » Nov 6, 2015
    Greetings sharonyanddave,

    Please don't take my comments as meaning the AGS is perfect and my apologies if what I said regarding the dynamics is misleading. Perhaps it would be better if I said it's the best cut grading system out there in certain respects and particularly to light performance. Welcome to the forum.

    Kind regards,
    Rhino
     
  21. Rockdiamond
    Ideal_Rock
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    by Rockdiamond » Nov 6, 2015
    Truly amazing points sharonyanddave. For a long time AGSL has been touted here on PS as superior for cut grading - and the reasons do not hold up to scrutiny.
    I'm not a scientist, but I have been looking at and working with diamonds my entire adult life- the AGSL cut grading system is missing a vital component regarding scintillation. IN the case of round diamonds, this shortcoming is less pronounced than in fancy shapes. But the underlying issue exists in both round and fancy shapes. Princess cut is a good test case because this shape is about the only shape which AGSL cut grading is utilized by the trade at large and this shape in particular highlights the disconnect between what real people actually like to look at and AGSL light performance standards and practices. To simplify the differences: AGSL rewards larger bright reflections versus more plentiful, and smaller flashes as the diamond moves.
    When considering round diamonds, GIA's top cut grade includes more stones which are stronger in scintillation. The result is that a significant percentage of observers will prefer GIA EX stones that AGSL dings.

    Having said that, I do agree that in general AGSL cut grading is "tighter". That means if you are a person that loves stones that follow the AGSL formula, buying an AGSL graded stone is likely to give good results.
    AGSL is a brand. That aspect oft times gets swept under the "scientific superiority" rug. Many of the writers on PS that tout the superiority of AGSL are sellers of AGSL stones.
    Plus, it seems that lately AGSL is a bit softer on clarity than GIA which has promoted some cutters who only used to use GIA to start using AGS.

    Personally I am very grateful for AGSL's existence, as well as the work they have done. But it needs to be put in perspective.
     
  22. Texas Leaguer
    Ideal_Rock
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    by Texas Leaguer » Nov 6, 2015
    RD,
    Like everyone else I am here to learn. So I am curious about a couple of your assertions.
    What lab do you think is superior for cut grading and why?

    Good of you to simplify, but can you explain how you arrived at this conclusion?

    Or this one:
    You wouldn't be just throwing things against the wall to see what sticks would you?
     
  23. Rockdiamond
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    by Rockdiamond » Nov 6, 2015
    HI Byran,
    I think that there's no absolute answer. If you're a person that loves the type of stone that AGSL does not, than GIA is the better lab. Overall, GIA is the more widely accepted lab, I don't think there's any debate about that.
    As I mentioned, if one is committed to getting a stone that is cut to AGSL standards, than clearly AGSL is the better lab. AGSL does a more thorough examination, I agree- but that fact in and of itself does not necessarily make the AGSL grade better for everyone.

    Just have a look at manner in which AGSL interprets ASET imagery- there' plenty of charts here on PS advocating how red is "better than" green for example.

    Well cut stones where the hearts and arrows do not line up perfectly will, in general, show more scintillation. Sometimes perfect optical symmetry is not a desirable look for many observers. Many more such stones get GIA EX cut grade than AGSL 0- which gets GIA blasted here regularly.
    In response to your question about the spaghetti theory......You wouldn't use science to claim superiority just because your company promotes AGSL would you?
     
  24. Texas Leaguer
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    by Texas Leaguer » Nov 6, 2015
    Thanks for taking the time to support your criticisms. That always helps people understand how valid they are.

    I'll answer your last question with a question: Why would a company NOT use science to support technical claims about their products? Look around - that is pretty common in the modern world.
     
  25. Rockdiamond
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    by Rockdiamond » Nov 6, 2015
    About the science, here's one example- "our world is lit from above"
    An irrelevant statement, even if it wasn't broadly inaccurate.

    This affects many other conclusions such as ASET interpretation of "red is better than green"

    I'm not a scientist, but I have though so much about this.
    Is a direct reflection of light better than a reflected reflection?
    The direct reflection is likely brighter- but is that necessarily better?

    If the light is entering the diamond through the crown ( green in ASET) it's far more likely to bounce around the diamond before exiting. Seems intuitive that means the light must loose intensity as it bounces.
    But when looking at actual stones that have a lot of dispersed green- or a well cut RBC non H&A with a more "mottled" ASET - sometimes the fact that there's more flashes of light compensates for the additional brightness of a larger, directly reflected light beam.

    My experience is that there's a disconnect between AGSL cut grading, and scintillation.
    AGSL methodology and science work extremely well for one type of stone- and basically ignore other types.

    Bryan- truly to put this to rest- I can't think of a better example of a great diamond seller than your company. Speaking as someone who looks at diamonds all day on the web, I am always impressed with the quality and integrity of your company.
    I want to make sure that our discussions are not seen as a knock on your company- or you.

    That you and I persaonlly disagree on certain aspects of cut, and how to assess it is, in my opinion, and important discussion.
    Here, we are discussing diamonds in a broader sense, I think commercial interests are best left out of the discussion. I know that is difficult, and sometimes it may have us at odds- sorry for that.
    I'm not "throwing stuff on the wall to see what sticks", I honestly believe that AGSL science leaves a sizable slice of well cut diamonds on the floor.
    Where I used to dismiss the science for that reason, I'm way past that.
    There is a hole in the AGSL system- which does not invalidate the positive aspects.
    But finding ways of "plugging that hole" would benefit consumers and the industry as a whole.
     
  26. Texas Leaguer
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    by Texas Leaguer » Nov 6, 2015
    I guess some people choose to focus on the donut and some on the hole. But because a donut has a hole does not make it less worth eating. :wink2:
     
  27. sharonyanddave
    Rough_Rock

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    by sharonyanddave » Nov 6, 2015
    We do agree on the bolded part, their cut grading even with its limitations is much more advanced than other lab. Cheers thanks.
     
  28. bqd251
    Rough_Rock

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    by bqd251 » Nov 7, 2015

    Sorry, but you're quite clearly making assertions or conclusions that aren't true. It stems from your misunderstanding of how light rays function. As a result you aren't correctly interpreting ASET maps.

    Are you claiming light entering from the table is more directly reflected back through the table? If so then why do Idealscope images often show the area under the table to be the lightest shades of red or even pink -shouldn't they be the deepest red? Afterall, aren't IS images supposed to measure intensity of light return?
     
  29. sharonyanddave
    Rough_Rock

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    by sharonyanddave » Nov 7, 2015
    From a scientific perspective Sassian and AGSL did a lot of work on scintillation I know that the 15 degree tilt dataset that they chose for many metrics is in part derived from the fact that scintillation events in a round brilliant occur in greatest frequency between 0 and forward tilt of 15 degress.

    However a conscious decision was made not to 'grade' scintillation or include a large part of the original research which utilized scintillation maps because preferences based on scintillation are highly subjective. Whether one prefers a smaller number of slower and larger flashes or a large number of smaller and faster flashes is a preference that an objective system based on optical science should not decide.

    There is no connection whatsoever and it is intentional.
    The word larger should be removed from this sentence.

    I think this is where you are misinterpreting their system, the brightness metric makes deductions for the surface area of the crown that is not capable of returning high angle light. It makes no distinction between a large flash or a small one. An Old European Cut (OEC) with larger, broader and slower flashes or a Star108 with very small, faster flashes can receive the AGSL top grade just like the Modern Round Brilliant Tolkowsky Cut.
     
  30. gm89uk
    Brilliant_Rock

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    by gm89uk » Nov 7, 2015
    Thank you for the info!
     

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