Consumer advisory: GIA Cut Grade Rounding Problems

[Serg]

re:Studying the lighting envirement in that box was science.
Saying the gia box had the same problem is a hit in my opinion unless there is proof the gia box has the problem

Do you think GIA light box can model " real world light conditions" ?

Any light box like GIA light box can not model any real light CONSUMER condition correctly. It is easy to proof

 

[belle]

Date: 2/3/2006 11:50:52 AM
Author: Serg
re:Studying the lighting envirement in that box was science.
Saying the gia box had the same problem is a hit in my opinion unless there is proof the gia box has the problem

Do you think GIA light box can model '' real world light conditions'' ?

Any light box like GIA light box can not model any real light CONSUMER condition correctly. It is easy to proof

have you proved that yet?

 

[adamasgem]

Date: 2/3/2006 10:41:45 AM
Author: sylvesterii

I disagree that the SAT is a true measure of how competent one is, and that an A at harvard is better than an A at a different institution, but there are a lot of issues within that not related to the comparison with which you were making it.

Relative to your comment to Bill Bray above, but a little off the subject. I'll both agree and disagree with you, with this food for thought from experiance.

1) I had friends at MIT with perfect SAT scores who flunked out of school because the couldn't hack the pace..

2) When I was a Sophmore at MIT a long time ago, I remember tutoring a Harvard Senior in arithmatic I had in High School

3) In the core sciences (Math, Physics, Chemistry) we were using the same texts as RPI and Cal Tech, yet would go through the same texts twice as fast, and on to bigger and better things

4) Last year, at the university I was teaching a course in Gemology at, I gave a handout on elementary trig of a right triangle and told the students they better know the concepts. On a midterm exam only 45% could define the sine of an angle of a right triangle conceptually (opposite over hypotenuse)

And lastly, one only needs to examine the GIA courses of the 1950's with the GIA "requirements" of today.

The "politically correct" trend most EVRYWHERE is to dumb everything down to the lowest common denominator

 

[adamasgem]

Date: 2/3/2006 12:07:27 PM
Author: belle

Date: 2/3/2006 11:50:52 AM
Author: Serg
re:Studying the lighting envirement in that box was science.
Saying the gia box had the same problem is a hit in my opinion unless there is proof the gia box has the problem

Do you think GIA light box can model ' real world light conditions' ?

Any light box like GIA light box can not model any real light CONSUMER condition correctly. It is easy to proof

have you proved that yet?

Belle: The proof is obvious to the causal observer, not unless every consumer carries the box around with them and wears the same clothes and is the same height and etc, etc, etc. The box (or any open box) is not a closed environment and is influenced by its envirionment.

But more importantly, the GIA CVE (Common Viewing Envirionment) box IS NOT WHAT IS USED TO GENERATE THEIR METRICS...

Their obscured hemisphere is what apparently "best fit" their "observational" studies, the tail wagging the dog in this case, what did the "trade" like.. The GIA "Taste Test", or what will sell more diamonds...in my opinion..

 

[Garry H (Cut Nut)]

Date: 2/3/2006 2:20:34 PM
Author: adamasgem

Date: 2/3/2006 12:07:27 PM
Author: belle

Date: 2/3/2006 11:50:52 AM
Author: Serg
re:Studying the lighting envirement in that box was science.
Saying the gia box had the same problem is a hit in my opinion unless there is proof the gia box has the problem

Do you think GIA light box can model ' real world light conditions' ?

Any light box like GIA light box can not model any real light CONSUMER condition correctly. It is easy to proof

have you proved that yet?

But more importantly, the GIA CVE (Common Viewing Envirionment) box IS NOT WHAT IS USED TO GENERATE THEIR METRICS... Marty I beg to differ - there were 18,000 dome observations compared out of +70,000 total observations which suggests about 20% were done in the dome.
But the fact that the dome with 46 degrees of darkness was the one they used the most suggests that the CVE Diamond Dock lighting box approximates an unrealistic viewing environment. For instance I have a shallow crown diamond (GIA would call it Good)here that when I show it to many clients and staff they very much like it - When compared to stones that gIa would grade as Excellent the shallow stone is often favoured as the best.
Note to this quote - (like a person who looks at a diamond from a
mostly fixed position and from a reasonably close
distance, in this case about 14–20 inches—roughly
35–50 cm—as we noted in most trade observations). So, if we agree, as I do, that means the 46 degrees of obstruction of lighting is simply ridiculous!!!!
But if you model the stone in a 46 degree darkened environment it looks like a dog. It would presumably look like a dog in the CVE lighting box. But diamonds that we would all agree were too deep and leaky would look better (for reasons you described earlier).

Their obscured hemisphere is what apparently 'best fit' their 'observational' studies, the tail wagging the dog in this case, what did the 'trade' like.. The GIA 'Taste Test', or what will sell more diamonds...in my opinion..

Edited 1/2 hour later

 

[Garry H (Cut Nut)]

When you use the word "METRICS" I think back to the time I asked Ilene Reinitz a question at one of the GIA presentations just after they employed Al Gilbertson and started "observation testing" (You may have been there?).
She had a problem or 2 answering some of mine and my proxy questions from Sergey about their Computer Metrics. I followed with a quaestion like "what if your computer metrics anad the observation testing did not agree?" She responded alnong this line "We have no problem in not using the computer metrics if they do not agree with human observer testing"

Now if you read the Foundation article carefully you can see that they have essentially dropped the computer metrics which are described here http://www.gia.edu/pdfs/cut_table_2.pdf

Here is a quote:
Of these 165 diamonds, the overall
cut appearance for 95 (58%) was accurately predicted
using brightness and fire metrics alone. In addition,
all the diamonds were within one category of
the predicted result based only on a combination of
calculated brightness and fire results.
Obviously, additional factors played a significant
role in the observation results for the remaining
42% of these diamonds. Hence, the next stage of
our investigation concerned how to identify and
correctly evaluate those diamonds for which the
brightness and fire metric results alone did not
accurately predict overall cut appearance, without
affecting the results for diamonds already adequately
“predicted.”
From http://www.gia.edu/pdfs/cut_fall2004.pdf
They go on to explain how they tried to make the data match observers opinions by accounting for ‘pattern’ – but later they admit they have no metric for scintillation (which they break down to pattern and sparkle). They decided ‘sparkle’ was adequately predicted and covered by the Fire Metric. Well helloooooo? Did I miss something? Their METRICS were wrong 42% of the time.

So please Marty, do not be fooled into believing the Metrics count for diddly squat.

 

[adamasgem]

Date: 2/3/2006 7:13:32 PM
Author: Garry H (Cut Nut)

When you use the word ''METRICS'' I think back to the time I asked Ilene Reinitz a question at one of the GIA presentations just after they employed Al Gilbertson and started ''observation testing'' (You may have been there?).
She had a problem or 2 answering some of mine and my proxy questions from Sergey about their Computer Metrics. I followed with a quaestion like ''what if your computer metrics anad the observation testing did not agree?'' She responded alnong this line ''We have no problem in not using the computer metrics if they do not agree with human observer testing''

Now if you read the Foundation article carefully you can see that they have essentially dropped the computer metrics which are described here http://www.gia.edu/pdfs/cut_table_2.pdf

Here is a quote:
Of these 165 diamonds, the overall
cut appearance for 95 (58%) was accurately predicted
using brightness and fire metrics alone. In addition,
all the diamonds were within one category of
the predicted result based only on a combination of
calculated brightness and fire results.
Obviously, additional factors played a significant
role in the observation results for the remaining
42% of these diamonds. Hence, the next stage of
our investigation concerned how to identify and
correctly evaluate those diamonds for which the
brightness and fire metric results alone did not
accurately predict overall cut appearance, without
affecting the results for diamonds already adequately
“predicted.”
From http://www.gia.edu/pdfs/cut_fall2004.pdf

They go on to explain how they tried to make the data match observers opinions by accounting for ‘pattern’ – but later they admit they have no metric for scintillation (which they break down to pattern and sparkle). They decided ‘sparkle’ was adequately predicted and covered by the Fire Metric. Well helloooooo? Did I miss something? Their METRICS were wrong 42% of the time.

So please Marty, do not be fooled into believing the Metrics count for diddly squat.

Yah, What they say is that they didn''t know how to model their "observations". Twp problems, inadequate models to predict and or correlate with observations conducted in unrealistic envirionment results in GIGO..

 

[Garry H (Cut Nut)]

Date: 2/3/2006 9:01:46 PM
Author: adamasgem

Yah, What they say is that they didn''t know how to model their ''observations''. Twp problems, inadequate models to predict and or correlate with observations conducted in unrealistic envirionment results in GIGO..

I think it is the other way around Marty, and quite a big fundemental issue.
They did a lot of computer based research that many of us involved here in these discussions published information to identify flaws in their approach.

They then appear to have moved to a new paradigm (observation testing), but tried to incoporate the older flawed material (probably so the Board did not shoot them for wasting 10''s of millions).

Using this approach they made a mess of the whole thing.

The more I go back over what evolved, the more it seems that the GIA Cut Study has produced an unbelievably poor result - and now we see they have no ability to even decide if a beautiful diamond with an additive indexing (tricked up) diamond is Excellent, Very Good, Good or Poor.

What a mess.

 

[valeria101]

Date: 2/3/2006 10:32:50 PM
Author: Garry H (Cut Nut)


They then appear to have moved to a new paradigm (observation testing), but tried to incorporate the older flawed material (probably so the Board did not shoot them for wasting 10's of millions).

Is it even the case that every result weekly related to diamond cut add up to the current GIA results? To me, it sounds like much of the past results were unconnected and only became 'background' to the current cut grades after the fact. With allot of patchwork involved, as you say. As if allot of the 'weight' thrown behind their conclusions is mostly deadweight.

Until 'Nature' catches up with this (as a previous post of yours wishes

) , it can't hurt to 'rework' their background evidence as much as feasible given public evidence and set the conclusions free online on a dedicated site. Consumer-friendly section included.

If reproducing these results fails... it would say allot.

 

[Serg]

Please, see very interesting examples for all cut grade system.

What is your idea about GIA cut grade for this examples?
What is your idea about adequate cut grade for this example?


This diamond has crown and pavilion painted. I will publish 3d model in next post
I will publish full report and my comments in Monday - Tuesday

 

[Serg]

Gem file

 

[Serg]

IS image jpg file

If you want receive similar image in Diamcalc you need increasing head size from 9 to 12 mm

 

[valeria101]

In case votes from the spectator public count...

Date: 2/4/2006 6:58:03 AM
Author: Serg



What is your idea about GIA cut grade for this examples?

Facetware says 'very good' but they must have downgraded because of the painting... so "good" sounds probable.



What is your idea about adequate cut grade for this example?

Oh well, it sounds like every effort was made to reduce contrast on this stone. It's nice, but a bit more polishing and it would have looked like a very nice single cut. Since it is not one of those, the looks may deserve some discounting after all. If it were a larger diamond, this would have been allot worse for me than it is on this 5mm example. I don't have a 'personal cut scale', if I did... this may have ended a step below the top.

 

[adamasgem]

Date: 2/4/2006 6:58:03 AM
Author: Serg

Please, see very interesting examples for all cut grade system.

What is your idea about GIA cut grade for this examples?
What is your idea about adequate cut grade for this example?





This diamond has crown and pavilion painted. I will publish 3d model in next post
I will publish full report and my comments in Monday - Tuesday

Well

1) Weight was pushed over a weight boundary by pavillion painting
2) EF/Naturals/Alignment
3) 1 degree max mins on crown and pavilion mains
4) Seems, from the charts to be in the EX range for GIA Table/Cr/Pav but didn't do the FacetWare
5) The symmetry grade of Good I might agree with
6) Girdle seems to be a tad thick for the verbal description, but under what day's definition I don't know
7) I calculated a 41.43 average pavilion angle not 41.6 as advertized (Sarin vs Helium/rounding ???)
Ana say it got a VG FacetWare

 

[strmrdr]

lets start it thru the filter...
using the crap rounded gia sarin data:


Selected: 59.6% depth, 60% table, 32.5° crown angle, 41.6° pavilion angle
The result is for a symmetrical diamond with a medium girdle and very good polish
HCA scores were adjusted Dec. 15, 2001 and Feb. 6, 2003.


Factor Grade
Light Return Good
Fire Good
Scintillation Good
Spread
or diameter for weight Excellent
Total Visual Performance 4.5 - Good - Only if price is your main criterion

Fails the first step of the strmrdr ring use cut grade system :}
strmrdr scale grade of: woofer

 

[strmrdr]

aset:
Not enough blue, fails test 3, test 2 is IS which it failed for not enough black.
guess: ags 7

 

[strmrdr]

very bright diamond but would have little fire because of the low contrast.
It would make a bright pendant but I wouldnt want it in a ring.

 

[strmrdr]

If this diamond performed as predicted I actualy might like it in person.
I like bright rounds.
I wouldnt put it in a ring but in a pendant if it came with the right discount for the cut quality id consider buying it.
Its a bright spready stone.

 

[strmrdr]

compared to a: 34.2, 41, 56t,60%star,80% lgf DC simulation, office lighting setting.

 

[adamasgem]

Date: 2/4/2006 1:36:05 PM
Author: strmrdr
aset:
Not enough blue, fails test 3, test 2 is IS which it failed for not enough black.
guess: ags 7

The current evolutions of the GIA/AGS/MSU systems all look at the faceup view. AGS and MSU currently also look at the performance of the diamond at 15 degrees (AGS) and 30 degrees(MSU).
With compter power advancing by leaps and bounds, I have no doubt that AGS will also start looking at a greater ensemble of tilt and azimuth angles to improve their system and metrics, as each tilt (or azimuth) gives you a different perspective of the stone.

You can play with this in diamondcalc.. I suggest that one starts tilting at 1 degree increments with the ASSET model, so that you will get an idea how and where the shift in "light grabbing" occurs (blue/red/green), which will give you an idea of what is going to happen to the stone when the wearer looks at it.

This was addressed by me in an old PS thread. It deals with how a consumer is going to perceived their stone when they are wearing it. Wheen you bring up your hand to view your ring, the natural position or viewpoit is that your eyes are somewhere about 20 to 40 degrees from the table of the stone. Ergonomically, one has to twist and "strain" their wrist their wrist to view the stone in the face up position.

There is a different probability distribution for viewpoints depending on whether the wearer is the viewer or someone else is seeing the stone on your hand. That is why I agreed with GIA, in their initial brilliance study about the concept of "weight light return" (I disagreed with their black hole lighting envirionment however, and still do in their current 23 degree obscuation model). But they dropped that concept (50-50 chance of getting it right and they picked the wrong choice)

Play with the tilts using the ASSET lighting with different stones, you will find it interesting and enlightening.

 

[strmrdr]

Marty,
agree on hand viewing positions.
Is ags using 15 degrees or 45?
Iv heard both from people who should be in the know.

 

[strmrdr]

0 to 15 degree DC aset
Bright but not a whole lot of scintillation because of the low contrast.

 

[strmrdr]

same as used as a comp above.
34.2, 41, 56t,60%star,80% lgf

edit: ignore the jpg info box .. thats what i get for doing screen shots in a hurry. bleh.

 

[oldminer]

In simple terms, what can someone take away from these images and postings? Is a lay person supposed to be able to judge how nicely a diamond will look from these colored images? Who is in a position to judge best how to find most attractive stone? Is anyone suggesting that dealers, appraisers or consumers will be able to select the best stones from these images? Or, are we still stuck in what obscuration and ligthing to adopt?

Love to hear some concise and simple advice on these questions. This is not a personal attack on ayone, so please refrain in return. THANK YOU

 

[strmrdr]

Date: 2/4/2006 4:48:22 PM
Author: oldminer
In simple terms, what can someone take away from these images and postings? Is a lay person supposed to be able to judge how nicely a diamond will look from these colored images? Who is in a position to judge best how to find most attractive stone? Is anyone suggesting that dealers, appraisers or consumers will be able to select the best stones from these images? Or, are we still stuck in what obscuration and ligthing to adopt?


Love to hear some concise and simple advice on these questions. This is not a personal attack on ayone, so please refrain in return. THANK YOU

In the tilted aset images as the colors shift and change so does the light return in those areas
less shift/change == less scintillation
where scintillation is defined as: dynamic contrast combined with dynamic fire.

They tell me that first would be very bright but because there is little shifting and changing of color there would be little scintillation compared the second set of images.

The person buying it is the best judge, like I said in person I can almost bet id like the diamond.

They are not the total picture but part of the puzzle.
There is no one piece of data that by itself tells everything about a diamond including spending a few minutes looking at it under limited or tricked out light conditions.

 

[strmrdr]

here is the gem file for my comparison model.
open both it and the one above side by side and set both to office lighting and hit play on both of them.
This one will dance more because it has more scintillation.

 

[adamasgem]

Date: 2/4/2006 4:48:22 PM
Author: oldminer
In simple terms, what can someone take away from these images and postings? Is a lay person supposed to be able to judge how nicely a diamond will look from these colored images? Who is in a position to judge best how to find most attractive stone? Is anyone suggesting that dealers, appraisers or consumers will be able to select the best stones from these images? Or, are we still stuck in what obscuration and ligthing to adopt?

Love to hear some concise and simple advice on these questions. This is not a personal attack on ayone, so please refrain in return. THANK YOU

Dave The ASSET images tell you from what angles the diamond is collecting its light from.. Typically, the highest angle lighting (blue) is the strongest in intensity, but it might be obscured by the viewer, but it has the highest efficiency of light return to the viewer, the green(low angle lighting) requires that there be lighting there otherwise you get dead zones, the red is the angle zone where one expects most of the light to occur from..

 

[adamasgem]

Date: 2/4/2006 4:47:40 PM
Author: strmrdr
same as used as a comp above.
34.2, 41, 56t,60%star,80% lgf

edit: ignore the jpg info box .. thats what i get for doing screen shots in a hurry. bleh.

Good job Storm..

Now if do the same sequence with a photoreal rendering in realistic lighting, but out to 45 degrees, and you will see where the stone will get bright, then dead, etc

Try it with different cuts and you will see that the worst "dead" spot shifts from one tilt to another tilt angle versus cut.. Showing that one or two tilts may not give you the "best" metric for a stone and that you have to look at as many perspectives as you can..

Of course, depending on the lighting model chosen, the photoreal perspective (as well as the real perspective) of the "goodness" of the cut will change... The "trick" is to develop metrics that reflect a realistic emsemble of viewing conditions
and lighting.

 

[adamasgem]

Date: 2/4/2006 5:13:33 PM
Author: strmrdr
here is the gem file for my comparison model.
open both it and the one above side by side and set both to office lighting and hit play on both of them.
This one will dance more because it has more scintillation.

Now you are learning... But you also have to consider if there is no low angle lighting, remember, there are usually light absorbers in a room at low angles... In cluding your body..

 

[strmrdr]

here is an asscher out to 45 by 2 degree steps they take over an hour to do so ill have to add it to my too do list for a round.