Belle, In part I agree with you, in that there is more informatation which would seemingly "protect" the general consumer who doesn''t look at a stone in the more quantified viewpoint of the PS viewer. Maybe less ability for flim flam.
strm…from what I can tell you’re mostly right on angular measurements but what’s wrong with the helium depth and table data on princess?...and table data on rounds?
the depth and tables are far off…3 of the 4 angle averages on those 2 stones match up like you said in degrees but pavilion and crown % are off.
on rounds the depth now matches but the tables are up to .6 off! ...3 of the 4 angle avgs match up in degrees like you said though one would be .1 away when rounded and another is close to .1 off.
oh i agree with you too marty…you can see in my previous post that i try to be attuned to ps and our critical standards as well as the larger public interest. for instance i want to see labs and scientists agree on things like helium, but that doesn’t mean .1 is necessary for every consumer out there. it isn’t. i’m with those who want to hold gia accountable while still being happy to see forward progress in the world.
Date: 1/24/2006 4:58:31 PM
Author: belle
strm…from what I can tell you’re mostly right on angular measurements but what’s wrong with the helium depth and table data on princess?...and table data on rounds?
princess 6587308…ags…73.1, 68.4, 39.7, 37.0, 59.0, 11.8…gog…72.7, 66.4, 39.69, 36.78, 59.2, 11.6
princess 6624602…ags…72.0, 69.0, 39.6, 37.9, 58.2, 10.9…gog… 71.7, 68.0, 39.55, 37.54, 58.0, 11.0
the depth and tables are far off…3 of the 4 angle averages on those 2 stones match up like you said in degrees but pavilion and crown % are off.
round 6630909…ags…61.9, 54.8, 40.9, 33.9, 43.2, 15.4…gog…61.9, 54.2, 40.85, 33.93, 43.1, 15.5
round 6358008…ags…60.3, 56.4, 40.8, 34.9, 43.1, 15.4…gog…60.3, 56.0, 40.79, 34.83, 43.0…15.4
on rounds the depth now matches but the tables are up to .6 off! ...3 of the 4 angle avgs match up in degrees like you said though one would be .1 away when rounded and another is close to .1 off.
i am surprised to see variations because the talk has been about how helium is so exact…sarin reports i see sometimes differ by .1 or .2…helium gets c/p angles within .1 but tables are not so precise…and wow.. do the princess numbers have a way to go yetthe tables seem very important to be off by half a degree with the kind of accuracy people have been claiming...maybe my expectations are too high...i am being hyper critical here.
we are talking accuracy here. how many times have you done this?
The most advantage Helium 3D model is correct azimuth angle. It is very important for raytracing analysis. Other parameters is not worse than from other Scanners( usually its are better). Heights are not very important for cut grading by raytracing, difference Table in 0.5% is not important for appearance diamond at all.
dave..knowing that is helpful. i have come to understand accuracy is a holy grail. my expectations might have been raised because of some helium hype here
okay..i''ll take care of the princess cuts then
new dqd''s july and oct 2005
i''m not talking about models. you said that in comparing virtual models to the real thing, the helium models were much more accurate. i wanted to know how many of these virtual to real comparisons you actually made as opposed to what was reported to you.
http://www.goodoldgold.com/Diamonds2005/1557/ags.jpg
Dave.. You need a combinaton of both methodologies, modeling and direct measurement, in my opinion. This is such that you don''t get into the quagmire of basing an overall conclusion on one vewpoint or envrironment for the stone, either of which that the consumer may never see.
by comparing i mean comparing generated IS images and heart images and arrow images against the actual images of the diamond.
And that highlighted phrase will require both liniar/angular measurements and modeling..
I think that is what GIA based most of their final work on, however, they might have used a few too many Helen Kellers in their survey. You know what they say about opinions, everyone''s got one.Date: 1/25/2006 4:28:48 PM
Author: valeria101
. Perhaps someone should come up with a system to measure clients'' likes and dislikes toobut until then, the method used to cutoff grades seems to be based on extrapolation from survey data (either formal or not). Not only ''prediction'' but also prediction without much corrective feedback until now (since cut grading systems are so young, and their users have other concerns - such as selling and buying diamonds).
Storm I guess I will have spank you.
The large survey must have been heroic, but I am a bit skeptical that ''preferences'' over diamond quality is something unchanging and hence measurable. Working with demographic data has made me rather cautious about what surveys can and cannot do: for example, I wonder how they could separate results for the visual impression of something rather abstract (brilliance) that can hardly be separated in practice from joint characteristics - like the shape and size of the ''objects'', not to mention the other fairly abstract elements of scintillation and fire... Etc. They must have tried hard indeed
Date: 1/25/2006 5:46:26 PM
Author: adamasgem
Storm I guess I will have spank you.
This is incorrect given my conversation today with Pete Yantzer at AGS.
I was told, that right now, currently, they only take Helium measurements when there seems to be a problem with the Sarin scans, like typically happens with shallow crown angles or painted girdles, a problem I have addressed on other threads with the apparent lack of meet point faceting generated from Sarin scans.
Yup, self fullfilling could be the operative word.Date: 1/25/2006 5:50:34 PM
Author: valeria101
The large survey must have been heroic, but I am a bit skeptical that ''preferences'' over diamond quality is something unchanging and hence measurable. Working with demographic data has made me rather cautious about what surveys can and cannot do: for example, I wonder how they could separate results for the visual impression of something rather abstract (brilliance) that can hardly be separated in practice from joint characteristics - like the shape and size of the ''objects'', not to mention the other fairly abstract elements of scintillation and fire... Etc. They must have tried hard indeed
For better or worse, GIA''s results may be authoritative enough to make their prophecy a self-fulfilling one. Sounds like good business to me
What might be even more interesting (and back on topic) is a comparison of the old AGS Ideal proportions range with the new GIA EX proportions range* ...Date: 1/25/2006 5:58:24 PM
Author: valeria101
Thanks. I should really have paid more attention to those before asking.
Clearly durability and brilliance make two and separating grades makes perfect sense. Surely you may guess where I've heard of that for the first time - thanks for the AGA grades
It would have been funny if both direct measurement and proportion-based grading of 'performance' would be present side by side on AGS paper. The previous exchange of posts on this thread about this matter made me wonder if the two grades overlap in estimating the same thing.
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