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New discovery Brilliant Ideal Cut (BIC) |
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| P: 7/24/2004 5:59:28 PM | |
Garry H (Cut Nut) Ideal Rock Total Posts: 11,577 Last Post: 11/22/2009 Member Since: 8/16/2000 |
I had a little chuckle when I saw this thread about why you can never predict the beauty of a diamond based on its outside measurements (actual title is "Diamond Beauty not limited to the Numbers"). As you can see if I had bothered to extend the crown angles on HCA - guess where we would arrive? I did not go that far because already I knew that people would call me a heretic for suggesting ideal cut parameters could go as far as 28 degrees!!! (By the way - the diamond would be getting into durability danger area with a Girdle .9-1.2% because the very shallow crown angle would lead to easy chipping.) 
Garry Holloway FGAA DipDT HCA and Ideal-scope developer http://www.ideal-scope.com and http://www.HollowayDiamonds.com.au |
| Posted: 7/24/2004 5:59:28 PM | |
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There are 17 replies to this message. There are 17 replies on this page. |
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| P: 7/24/2004 6:01:24 PM | |
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Garry H (Cut Nut) Ideal Rock Total Posts: 11,577 Last Post: 11/22/2009 Member Since: 8/16/2000 |
Oops Here is the link Garry Holloway FGAA DipDT |
| Posted: 7/24/2004 6:01:24 PM | |
| P: 7/24/2004 6:42:35 PM | |
chialea Ideal Rock Total Posts: 520 Last Post: 9/3/2004 Member Since: 4/20/2004 |
I've always been a bit confused about the contention that you can't get a good guess at various types of performance from the outside measurements of a diamond. I mean... we know the optical properties of the material, and we know some very advanced rendering techniques -- even raytracing is going to get you a very long way on something like this. It's physics, and not even the hard kind of physics. The less information you have, the bigger your error margin, but I would think it stranger to think that you couldn't model something like this reasonably well than that you could. EDIT: I'm not trying to disparage your work, Gary. I, and lots of others, really appreciate it. This is from the math-type point of view of "that's possible" not "that didn't take you any work"
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| Posted: 7/24/2004 6:42:35 PM | |
| P: 7/24/2004 7:08:00 PM | |
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Garry H (Cut Nut) Ideal Rock Total Posts: 11,577 Last Post: 11/22/2009 Member Since: 8/16/2000 |
The math is actualy very complex because it involves predicting what humans like to look at. A chess board is 1/2 as bright as a sheet of white paper, but twice as bright as the paper when it is moved 
Garry Holloway FGAA DipDT |
| Posted: 7/24/2004 7:08:00 PM | |
| P: 7/24/2004 9:27:06 PM | |
valeria101 Ideal Rock Total Posts: 14,048 Last Post: 4/30/2006 Member Since: 8/29/2003 |
----------------  So should step cut stones be judged by their "stereo" light return instead of considered less brilliant ?Ana "The greatest experts are only as good as the sum total of what they have seen." [Souren Melikian] |
| Posted: 7/24/2004 9:27:06 PM | |
| P: 7/24/2004 9:40:02 PM | |
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Garry H (Cut Nut) Ideal Rock Total Posts: 11,577 Last Post: 11/22/2009 Member Since: 8/16/2000 |
Good point Ana This is from Sergey and Yuri's presentation in Moscow. You can do a little experiment with it - put a piece of paper (envelope or something) between the two images so left eye sees left and right eye sees right side. Your mind sees the right hand side image  Garry Holloway FGAA DipDT |
| Posted: 7/24/2004 9:40:02 PM | |
| P: 7/24/2004 9:51:51 PM | |
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valeria101 Ideal Rock Total Posts: 14,048 Last Post: 4/30/2006 Member Since: 8/29/2003 |
I was wandering whether you guys had deliberately set the two types of brilliance measure in the Gem Adviser - the step cut facets make the static and stereo brilliance scores be rather far apart - this doesn't happen for modified brilliant cuts. This seems to contradict popular observation about tilt brilliance ... if the stereo effect is just judged as a sequence of static observations. So... now I know. Thanks This is one very clever way to superimpose images with no time laps involved. With the amount of detail that gets mentioned about OctoNus research you guys should have spent years on this! Ana "The greatest experts are only as good as the sum total of what they have seen." [Souren Melikian] |
| Posted: 7/24/2004 9:51:51 PM | |
| P: 7/24/2004 10:15:01 PM | |
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Garry H (Cut Nut) Ideal Rock Total Posts: 11,577 Last Post: 11/22/2009 Member Since: 8/16/2000 |
You can get big variances too with poorly cut rounds or princess that also display large leakage areas or very shallow stones with big darkness patches Ana. I think you are considering diamonds with less virtual facets (ie step cuts) as having more strong stereo effects - but you should compare these to not so well cut briliantined stones maybe. Garry Holloway FGAA DipDT |
| Posted: 7/24/2004 10:15:01 PM | |
| P: 7/24/2004 10:28:40 PM | |
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valeria101 Ideal Rock Total Posts: 14,048 Last Post: 4/30/2006 Member Since: 8/29/2003 |
---------------- Perfect guess This way I found out some reason why Old rounds and modern Ecs seem a (better) breed apart to me... they do have some optical effects in common at least if not much else Ana "The greatest experts are only as good as the sum total of what they have seen." [Souren Melikian] |
| Posted: 7/24/2004 10:28:40 PM | |
| P: 7/26/2004 12:08:28 PM | |
Mara Ideal Rock Total Posts: 27,897 Last Post: 11/21/2009 Member Since: 10/30/2002 |
The stone looks quite lovely and scores well on the IS2, BS and even shows hearts. Very nice. However, again what is never mentioned is that I don't know who would ONLY go by numbers when choosing a stone. If I saw that stone listed on a vendors site, with all the reports that it has on that thread, and priced accordingly for an AGS10 stone, I would definitely consider it IF that is what I was interested in. No one is saying that AGS0 is all that people should consider, but many of the AGS10 stones out there aren't going to be on some of these vendors sites NOR are they going to bother to run all the reporting on them. So automatically they would be disqualified from my shopping. That stone obviously has excellent symmetry and great light return, but how many of those AGS10 stones are going to look that good?? That's a one in a million it would seem?? So why look for a needle in a haystack when the hay is sweetly scented and sparkles so? 
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| Posted: 7/26/2004 12:08:28 PM | |
| P: 7/26/2004 3:39:52 PM | |
Paul-Antwerp Ideal Rock Total Posts: 1,902 Last Post: 11/20/2009 Member Since: 9/3/2002 |
Well Garry, While you only have a little chuckle, I still cannot stop laughing. This is hilarious. Certainly to think that this comes from people, who consider it their calling to tell that nobody can say anything about a diamond by its numbers only. I wonder if they could explain why this cutter produced a nice symmetrical stone with such non-conformistic proportions, while he is supposed to be capable of judging cut only after he finished his work, not by the numbers that he is cutting. Sorry Leonid, I could not refrain myself. Live long, Paul Slegers |
| Posted: 7/26/2004 3:39:52 PM | |
| P: 7/26/2004 4:30:00 PM | |
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Garry H (Cut Nut) Ideal Rock Total Posts: 11,577 Last Post: 11/22/2009 Member Since: 8/16/2000 |
---------------- The new world order of post GIA and AGS cut grade systems will change all that Mara - these stones will become desirable. trust me (I am a jeweler)  (that was a joke)I will see if I can dig up a photo to show what GIA like in proportions. This stone was probably cut and used as part of the GIA survey. Garry Holloway FGAA DipDT |
| Posted: 7/26/2004 4:30:00 PM | |
| P: 7/26/2004 4:44:14 PM | |
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Garry H (Cut Nut) Ideal Rock Total Posts: 11,577 Last Post: 11/22/2009 Member Since: 8/16/2000 |
---------------- We should expect no better Paul (BTW you are up very late!) Here is an example of another stones proportions that you might find in the GIA survey: DEPTH % 59.3% TBL % 56 CROWN ANGLE 23.6 PAV ANGLE 42.1 And lots of cutters know that they can make nice looking stones with these propotions (those that do not - I will consult for you )But you Paul, you prefer to cut exactly what the market wants - 40.6 to 40.7 pav, 34-34.6 crown etc etc 9and you do it extremely well. I suggest that this leads to a huge amount of wasted diamond in the world. Until we can get people in the trade to expect that BIC and FIC diamonds will sell, and develop selling methods to make them attractive to retailers, we will have a problem. But do not worry about consumers - they will love these new stones Garry Holloway FGAA DipDT |
| Posted: 7/26/2004 4:44:14 PM | |
| P: 7/26/2004 4:49:31 PM | |
Rank Amateur Ideal Rock Total Posts: 1,547 Last Post: 5/5/2009 Member Since: 2/26/2003 |
---------------- You mean you don't cut at random angles and then test them on the BrillianceScope to see which to brand as your own??? I am shocked. 
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| Posted: 7/26/2004 4:49:31 PM | |
| P: 7/26/2004 4:49:53 PM | |
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Garry H (Cut Nut) Ideal Rock Total Posts: 11,577 Last Post: 11/22/2009 Member Since: 8/16/2000 |
Here is a slide from the GIA GemFest in Basel April 2004 Garry Holloway FGAA DipDT |
| Posted: 7/26/2004 4:49:53 PM | |
| P: 7/26/2004 5:04:27 PM | |
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Rank Amateur Ideal Rock Total Posts: 1,547 Last Post: 5/5/2009 Member Since: 2/26/2003 |
must...attempt...to...stay...on...topic Garry Do you think all this cut technology will have a net effect of eliminating poorly cut stones? Will the rising tide raise all boats? Is it possible to make well-cut rounds from almost any rough if, as a cutter, you know all your options? Maybe some rough will always force the cutter's hand and he will always cut a dog or two out of ten. I guess I have no feeling for how much of this cut info is news to cutters and how much is things they know but don't do because it just isn't econonmically justified. R/A
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| Posted: 7/26/2004 5:04:27 PM | |
| P: 7/26/2004 5:06:49 PM | |
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Garry H (Cut Nut) Ideal Rock Total Posts: 11,577 Last Post: 11/22/2009 Member Since: 8/16/2000 |
Yes it will improve cut quality. No - many cutters wait for direction from their sales office, which is why I started here - with consumers. but you lot are sooo conservative too 
Garry Holloway FGAA DipDT |
| Posted: 7/26/2004 5:06:49 PM | |
| P: 7/26/2004 5:12:03 PM | |
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valeria101 Ideal Rock Total Posts: 14,048 Last Post: 4/30/2006 Member Since: 8/29/2003 |
Selling tools... of course I see the link to the Ideal Scope page. Surely I appreciate how this little red box lets one look beyond currenty cut grades (AGS's or what not). However, the Iscope is just as useful as it's refference chart. And then, the immage you built to compare with the Tiffany add is also a type of refference that can be used to judge diamonds. Even without the red box. The immages from GIA's presentation seem to look this way too. And so do the black and white "daylight" immages generated by your new rapid photo software. All in all, it sounds "elegant" and practical to judge diamonds using some refference chart of what well cut ones look like under prescribed, natural lighting conditions. No one would could possibly argue that such educated viewing is hard to bring into a jewelry shop. Just a thought, of course. Funny what you say about conservative consumers But even the tutorial here presents the H&A symmetry as perfection, the Iscope as means to choose among AGS0 graders. There is barely one stone outside this range with decent data to talk about, as Mara says! And no reasonable refference to interpret Iscope pics on fancies. And then, down under lies the Cut Adviser.  What are honest people to do? It takes an obsessive character (no ofense intended, of course) to read behind these lines.  Ana "The greatest experts are only as good as the sum total of what they have seen." [Souren Melikian] |
| Posted: 7/26/2004 5:12:03 PM | |
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