Light Performance vs Color

[John P]

Date: 10/15/2009 3:16:41 PM
Author: Allison D.

Where''s the Tabasco? I didn''t think Texans could cook without Tabasco?

I knew this thread was missing something...a discussion about FIRE.

Check.

 

[diagem]

Date: 10/14/2009 4:11:39 PM
Author: Serg

Date: 10/14/2009 12:08:09 PM
Author: AshNZ
Kark_K, to quote


''For example longer light paths == less performance is not correct.''


Sorry Karl, on it''s own (which is how you made the statement), this is incorrect. Longer ray length DOES equal less performance.

I don''t know how to make it clearer than that. Unless you want to prove to me that there is no such things absorbtion...

Perhaps jump on Wikipedia...


Now, I agree with you when you combine it with other elements, but in every case longer ray paths is bad (due to absorbtion), it is just completely outweighted by other factors.

Date: 10/14/2009 11:56:44 AM

Author: glitterata

Ash, what is your definition of ''light performance''?


Unless you have a solid definition that corresponds to some meaningful and desirable visual property of diamonds, optimizing it won''t do you a lick of good.

Good question. Firstly, is there an ''Industry Standard''?

My definition (simplistically) was the ''inverse of leakage'' Truth be told, I don''t have the knowledge to have a strong grasp on this just yet.


Ash

Hi Ash,
for your definition '' performance = "inverse of leakage"'', statement as ''longer light paths == less performance '' could be correct( if diamond has valuable absorption ). But your definition and several others what consider cut performance as Light return are not adequate to Diamond Beauty .

Diamonds with leakage even less than Round ASG0 H&A could be Ugly .Just it.

BTW. there are even several definitions what Light Return is.
Please think firstly about better definitions for colorless diamond performance

Thanks Serg..., that is actually the bottom line IMO.....
Almost everything can probably be measured...., except beauty

I have seen some amazingly beautiful "Table Cut" Diamonds that had about 80% of their "face-up" area translated into "leakage"..., some had body-colors and their symmetry was nothing to write home about..., but were still beauties....

 

[AshNZ]

Date: 10/14/2009 4:06:36 PM
Author: adamasgem

Date: 10/14/2009 1:10:31 PM
Author: AshNZ


Todd - I don''t pretend to know a lot about the industry but in a short space of time I haven''t seen a lot of faith in GIA from seasoned experts, this artical adds to that... Everyone makes mistakes, but I guarantee you the scathing write-up would be due to the lack of retraction and correction - Science demands self-regulation from peer reivew, GIA can''t be taken too seriously if they think they are above this process.

I can see how 3D modeling of LP would be difficult given in the infinite number of potential lighting sources/positions.

Ash

Ash.. that has been a long time problem with the self appointed world''s foremost authority, they don''t like corrections or peer review that is critical... The one good thing is that the editors of G&G don''t always let their piled high and deeps get away with it, and will publish letters to the editor, although the sanitization process to tone them down can be frustrating sometimes..

They are really good at covering up bribery and also at slinging mud for their own oligarcical $$$$ gain, a violation of the Lanham Act, especially when in a US Patent, but lawyers are expensive, I should have sued a long time ago...

Back to the subject at hand, you would be surprized at the amount of internal absorption in even a ''colorless diamond''. I''d have to dig out the results of forward 3D MonteCarlo studies I did (and published years ago on PS) to try to get comparison with GIA''s brilliance and fire studies of the late 90''s.
One can conviniently tweet the conditions of a metric, and add a bad taste test, such that most stones get an A, sort of like what has happened in our schools today, social promotion... we call it grade creep and BS. The only one that has been trying to keep the cut and color grading somewhat honest, appears to be AGS.
In the PS archives their are some interesting results as to the percentage of time GIA and AGS give a D color... On sample sizes exceeding 200,000 available graded stones, one is about three times as likely to get a D from GIA versus AGS. Now when it comes to secondary labs, we don''t have enough published data, but it appears you can guess how it will turn out....

I had talked with Dave and pointed out that GIA has a color grading patent which uses reflected light , which buries the signal characterization you are looking for on top of the 17% or more surface relection. There is some pointed comment about the GIA patent on my web site. http://www.adamasgem.org

Any luck digging up that work? David notes, that in discussion with you, that he is somewhat surprised by the level of light degredation you feel there is due to color. You have a lot of interesting information on your website but I couldn''t find anything relating to this topic specifically.

I am looking for a AGS graded D Fluorescent stone with no feather/cloud or heavy inclusions (VS2 or better) based on the outcomes of this tread so far

Ash

 

[adamasgem]

Date: 11/2/2009 11:32:15 AM
Author: AshNZ

Any luck digging up that work? David notes, that in discussion with you, that he is somewhat surprised by the level of light degredation you feel there is due to color. You have a lot of interesting information on your website but I couldn''t find anything relating to this topic specifically.

I found the summary XLS files and will try to put together an explanation of the runs I did, one of the problems is that I can''t find the record of which unnormalized absorption file I used five or six years ago..., but I can show my 50000 sample ray trace results with 250 runs of the 50 (changing) GIA WLR model published results, and the same 50 or so cuts done at 1ct, 2ct and 5ct scalings.



I am looking for a AGS graded D Fluorescent stone with no feather/cloud or heavy inclusions (VS2 or better) based on the outcomes of this tread so far

Ash

Ash A much better and safer value would probably be an E fluorescent stone, which precludes you paying big time for a possible, if not probable, borderline color call. Again, the possible $ difference depends on the clarity.
D/IF versus E/IF can sting you big time, even on a one ct stone, not so much as the clarity grade gets to VS1...

 

[AshNZ]

Date: 11/2/2009 12:35:46 PM
Author: adamasgem

Date: 11/2/2009 11:32:15 AM
Author: AshNZ

Any luck digging up that work? David notes, that in discussion with you, that he is somewhat surprised by the level of light degredation you feel there is due to color. You have a lot of interesting information on your website but I couldn''t find anything relating to this topic specifically.

I found the summary XLS files and will try to put together an explanation of the runs I did, one of the problems is that I can''t find the record of which unnormalized absorption file I used five or six years ago..., but I can show my 50000 sample ray trace results with 250 runs of the 50 (changing) GIA WLR model published results, and the same 50 or so cuts done at 1ct, 2ct and 5ct scalings.



I am looking for a AGS graded D Fluorescent stone with no feather/cloud or heavy inclusions (VS2 or better) based on the outcomes of this tread so far

Ash

Ash A much better and safer value would probably be an E fluorescent stone, which precludes you paying big time for a possible, if not probable, borderline color call. Again, the possible $ difference depends on the clarity.
D/IF versus E/IF can sting you big time, even on a one ct stone, not so much as the clarity grade gets to VS1...

Looking forward to the summary.

As it turns out I have my eye on an Infinity E color, Strong Blue Flu stone. I''ll be viewing it soon. Now another concern is color grading of Fluorescent stones.... but that''s another kettle of fish (I have read your thoughts on this - very interesting.. and slightly scary!)

Ash