Low LGF%? Need advice on this stone

[Cehrabehra]

Date: 7/15/2007 9:49:06 AM
Author: DiaGem

In the same way, 74% is not short. Add to this the difficulty of exactly measuring this percentage.

74% is in my opinion long..., i agree.

oh I love it DG - 74 is long! woooo!!!!!!

To the OP - it is really a matter of taste, I like the shorter lgf better myself, but have found an appreciation for the longer ones as well.

 

[JohnQuixote]

Date: 7/15/2007 12:42:24 PM
Author: echelon6
Also, the consensus of ideal LGF range I refer to can be found here: https://www.whiteflash.com/diamonds_info/t/all_about.aspx?articleid=299&zoneid=21

(In the criteria for ACA, it says LGF = 76-80%)

That's according to WF. But it's also been supported in numerous posts by Rhino, John Q, Garry and a few others (sorry, can't find the links right now)

I'm not aware of trade or even PS consesus, and if I've given that impression on the forum it was not intended. The numbers we hold to simply work for us. It's all a matter of overall configuration and taste. In near-Tolkowsky rounds it's possible to have anywhere from 67.5% - 87.5% lower half % and still get the top cut grade, so these middle numbers we're discussing are all in the bullseye.

We are guilty of overanalysis sometimes - that's what all this writing about something that sparkles can do.

 

[Cehrabehra]

Date: 7/15/2007 11:53:53 AM
Author: Wink

Consensus? Where is this consensus? I have not heard or seen it.

Wink

omg - this seriously made me chuckle.... ::high fives wink::

 

[JohnQuixote]

 

[diagem]

Date: 7/15/2007 12:09:07 PM
Author: Paul-Antwerp

Date: 7/15/2007 11:12:21 AM
Author: echelon6

Thanks for the reply, Paul. Very informative and I did learn a few things.

So basically LGF length is determined by the proximity of LGF and MPF angles - the closer they are, the larger the LGF.

But what I still don''t understand is why there''s a consensus that LGF should fall within 77-81%. There must be a reason, i.e. this range is optimum for overall well-rounded performance of a diamond, and any LGF outside this range should be cause for concern?

And I mean if it was 76%, I''d just accept it. But at 74%, that must be like 1 or 2 standard deviations away from the mean, amongst superideals. I certainly get that impression from my many hours of browsing vendor inventory...

If you consider that nowadays many cutters cut the LGF first and the main pavilion facets afterwards, it might lead you to think differently again.

????

I do not understand where you find that consensus. I do not see such consensus, and if you see it, it is probably due to a too limited selection.

Finally, the same stone measured on one machine compared to another could well give a different result by 2 to 3%, with the difference becoming higher as the LGF-% increases.

''Ground control to major Tom''

 

[JohnQuixote]

Date: 7/15/2007 11:53:53 AM
Author: Wink

Consensus? Where is this consensus? I have not heard or seen it.

LOL. We can ''consense'' on that! Unless you disagree.

 

[Garry H (Cut Nut)]

Date: 7/15/2007 9:47:04 AM
Author: junior35

Date: 7/15/2007 2:15:02 AM
Author: Garry H (Cut Nut)

Date: 7/14/2007 11:25:06 PM
Author: junior35
''Traditionally'' ,before the discovery of hearts and arrows ,the combination of 80/55 was widely accepted.That is 80% lgf and 55% star facets.
Later,it was noticed that shorter (e.g. 75%) lgf produce fatter arrows.So now we get to the sensitive area of taste.I personally like slightly fatter arrows (77%)(see attached pic) .But it seems that most of the industry likes 80%+(e.g.) thinner arrows .It''s a matter of taste.There is no right or wrong.

Wow Junior, that is one seriously painted stone!!!!!!!!!!
And the star facets are unusually short too?

I think a taste for this particular stone would be very personal. It would no doubt be very firey, but it would not have lots of brilliance?

Gary,this is a semi-finished stone from a Dialit automatic machine. It''s fully brillianteered on the bottom and 8/8 on the top.

 

[WinkHPD]

Date: 7/15/2007 3:42:34 PM
Author: JohnQuixote

Date: 7/15/2007 11:53:53 AM

Author: Wink


Consensus? Where is this consensus? I have not heard or seen it.

LOL. We can ''consense'' on that! Unless you disagree.

Okay, we can consense on that. We can also consense that you spent a LOT of time to put your very well done post together. Thank you for sharing it with us!

Wink

 

[Garry H (Cut Nut)]

May I please amplify John''s comment above that Lower girdle appearance is greatly amplified by table size (and also pavilion angle to a lessor extent).

 

[echelon6]

Thanks for all the replies, and a big thanks to John Quixote for your detailed input.

Its just that vendors here have previously said that 77-80 makes for an optimal tradeoff between white light / fire, so this leads me to think that the whole LGF issue is one of performance, not merely taste? i.e. I fear that 74 may be suboptimal in terms of the DCLR / brilliance tradeoff.

e.g. to illustrate my point with numbers (I know this is a crude or utterly wrong representation of what actually happens, but it highlights my concerns exactly):

At 77-80, Fire = 40%, White light = 60%, perfectly efficient diamond
At 73-77, Fire = 60%, White light = 30%, loss = 10% somewhat inefficient diamond
At 67.5-73, Fire = 70%, White = 10%, loss = 20% very inefficient

The "loss" (im just making terms up here) is not leakage as we understand it, but rather "loss" in perception of the diamond''s overall light return? e.g. human eyes might interpret fire / white light differently, and by moving the LGF outside of ideal ranges, it might make a dull-appearing diamond?

Please correct me if I''m wrong.

 

[WinkHPD]

Date: 7/15/2007 10:24:19 PM
Author: echelon6
Thanks for all the replies, and a big thanks to John Quixote for your detailed input.


Its just that vendors here have previously said that 77-80 makes for an optimal tradeoff between white light / fire, so this leads me to think that the whole LGF issue is one of performance, not merely taste? i.e. I fear that 74 may be suboptimal in terms of the DCLR / brilliance tradeoff.


e.g. to illustrate my point with numbers (I know this is a crude or utterly wrong representation of what actually happens, but it highlights my concerns exactly):


At 77-80, Fire = 40%, White light = 60%, perfectly efficient diamond

At 73-77, Fire = 60%, White light = 30%, loss = 10% somewhat inefficient diamond

At 67.5-73, Fire = 70%, White = 10%, loss = 20% very inefficient


The ''loss'' (im just making terms up here) is not leakage as we understand it, but rather ''loss'' in perception of the diamond''s overall light return? e.g. human eyes might interpret fire / white light differently, and by moving the LGF outside of ideal ranges, it might make a dull-appearing diamond?


Please correct me if I''m wrong.

Don''t know if we can make you believe it, it has been said many times already in this thread. Don''t have a clue where you are getting the information above, but it IS WRONG.

You need to go look at some diamonds to see this for yourself rather than creating these things in your mind. You will create a horrible injustice to some wonderful stones if you can convince people that the above is correct. Already Garry and John have shown you that lgf is a personal taste issue, not a performance issue. You are attempting to create facts that simply are not there. Why do you do this?

Wink

 

[WorkingHardforSmallRewards]

Date: 7/16/2007 12:06:59 AM
Author: Wink

Date: 7/15/2007 10:24:19 PM

Author: echelon6

Thanks for all the replies, and a big thanks to John Quixote for your detailed input.



Its just that vendors here have previously said that 77-80 makes for an optimal tradeoff between white light / fire, so this leads me to think that the whole LGF issue is one of performance, not merely taste? i.e. I fear that 74 may be suboptimal in terms of the DCLR / brilliance tradeoff.



e.g. to illustrate my point with numbers (I know this is a crude or utterly wrong representation of what actually happens, but it highlights my concerns exactly):



At 77-80, Fire = 40%, White light = 60%, perfectly efficient diamond

At 73-77, Fire = 60%, White light = 30%, loss = 10% somewhat inefficient diamond

At 67.5-73, Fire = 70%, White = 10%, loss = 20% very inefficient



The 'loss' (im just making terms up here) is not leakage as we understand it, but rather 'loss' in perception of the diamond's overall light return? e.g. human eyes might interpret fire / white light differently, and by moving the LGF outside of ideal ranges, it might make a dull-appearing diamond?



Please correct me if I'm wrong.

I think it is pretty clear where one of your areas of confusion is at, based on this post. I will do my best with my limited knowledge to begin addressing it, and if anyone feels obliged they can expand on it and explain where I may have confused something myself. Light can be very...tricky...to say the least, so I am sure that this is a very simplistic approach. Light enters the diamond through facets which will determine the angle at which the light travels as it passes through the diamond. It will then strike another angled surface. The angle of the second surface in relation to the angle at which the light strikes the surface will determine where the light travels next at which time it will strike another angle and continue traveling in correspondence with the guidance of that third angle. Thus it will be the angle of those facets and the angle of approach that the light is traveling when it strikes that facet that will determine X% of light return. If all goes perfectly 100% of what goes in will come back out the top, though I don't believe 100% itself is a very realistic goal.

LGF will have some bearing on exactly what manner that light is presented when it comes out, but in fact it does not really determine quantity of fire.

The first thing you need to consider when you are doing % examples such as those above are exactly what are you trying to measure? The number of flashes? remember, this is light, and it can be very difficult to measure in quantitative terms such as those, what exaclty does "more fire" mean?

I believe a more proper representation of the above equations would be written thusly:

Diamond A returns X% of light:

At 77-80, Fire = x%, White light = y%, 100-X% light loss


Diamond B returns Y% of light:

At 73-77, Fire = x%, White light = y%, with 100-Y% light loss


Diamond Z returns Z% of light:

At 67.5-73, Fire = x%, White = y%, with 100-Z% light loss

Bassically, the % of fire and white light should be fairly consistent but how they are presented changes. and even if that were incorrect depending on how you quantified light it would certainly follow for corresponding x, y that as x-a occurs so also y+a. but certainly not x-a, y+b where a does not equal b..that simply doesn't make any sense to me.

maybe I am just crazy, but that is a basic gist of what I understand to be the case.

 

[Garry H (Cut Nut)]

Date: 7/15/2007 10:24:19 PM
Author: echelon6
Thanks for all the replies, and a big thanks to John Quixote for your detailed input.

Its just that vendors here have previously said that 77-80 makes for an optimal tradeoff between white light / fire, so this leads me to think that the whole LGF issue is one of performance, not merely taste? i.e. I fear that 74 may be suboptimal in terms of the DCLR / brilliance tradeoff.

e.g. to illustrate my point with numbers (I know this is a crude or utterly wrong representation of what actually happens, but it highlights my concerns exactly):

At 77-80, Fire = 40%, White light = 60%, perfectly efficient diamond
At 73-77, Fire = 60%, White light = 30%, loss = 10% somewhat inefficient diamond
At 67.5-73, Fire = 70%, White = 10%, loss = 20% very inefficient

The ''loss'' (im just making terms up here) is not leakage as we understand it, but rather ''loss'' in perception of the diamond''s overall light return? e.g. human eyes might interpret fire / white light differently, and by moving the LGF outside of ideal ranges, it might make a dull-appearing diamond?

Please correct me if I''m wrong.

Echelon I think your anaolgy is brilliant, even though it has created already some firey debate (pun intended).

The data for fire according to the new beta version of DiamCalc3Pro supports the idea that fire increases as the LG''s get shorter.
This is the data for 60 LG length to 90 LGL
60.00 1.37230
61.00 1.35446
62.00 1.33476
63.00 1.31255
64.00 1.28992
65.00 1.26270
66.00 1.24256
67.00 1.22159
68.00 1.19733
69.00 1.17338
70.00 1.14903
71.00 1.13130
72.00 1.11789
73.00 1.10253
74.00 1.08152
75.00 1.06840
76.00 1.05799
77.00 1.04600
78.00 1.03335
79.00 1.01977
80.00 1.00700
81.00 0.99014
82.00 0.97760
83.00 0.96927
84.00 0.95445
85.00 0.94761
86.00 0.93675
87.00 0.93027
88.00 0.92516
89.00 0.92357
90.00 0.92288

My experiance tells me that as the LG''s get shorter the stone gets darker.
I expect you mean the loss is the loss of light return that comes from head extinction / obscuration as the mains get fatter. Of course that would depend on many factors - but as a stab in the dark (punny?) yours is as good as anyothers.

 

[whatmeworry]

Date: 7/16/2007 1:44:38 AM
Author: Garry H (Cut Nut)

Date: 7/15/2007 10:24:19 PM

Author: echelon6

Thanks for all the replies, and a big thanks to John Quixote for your detailed input.


Its just that vendors here have previously said that 77-80 makes for an optimal tradeoff between white light / fire, so this leads me to think that the whole LGF issue is one of performance, not merely taste? i.e. I fear that 74 may be suboptimal in terms of the DCLR / brilliance tradeoff.


e.g. to illustrate my point with numbers (I know this is a crude or utterly wrong representation of what actually happens, but it highlights my concerns exactly):


At 77-80, Fire = 40%, White light = 60%, perfectly efficient diamond

At 73-77, Fire = 60%, White light = 30%, loss = 10% somewhat inefficient diamond

At 67.5-73, Fire = 70%, White = 10%, loss = 20% very inefficient


The ''loss'' (im just making terms up here) is not leakage as we understand it, but rather ''loss'' in perception of the diamond''s overall light return? e.g. human eyes might interpret fire / white light differently, and by moving the LGF outside of ideal ranges, it might make a dull-appearing diamond?


Please correct me if I''m wrong.

Echelon I think your anaolgy is brilliant, even though it has created already some firey debate (pun intended).


The data for fire according to the new beta version of DiamCalc3Pro supports the idea that fire increases as the LG''s get shorter.

This is the data for 60 LG length to 90 LGL

60.00 1.37230

61.00 1.35446

62.00 1.33476

63.00 1.31255

64.00 1.28992

65.00 1.26270

66.00 1.24256

67.00 1.22159

68.00 1.19733

69.00 1.17338

70.00 1.14903

71.00 1.13130

72.00 1.11789

73.00 1.10253

74.00 1.08152

75.00 1.06840

76.00 1.05799

77.00 1.04600

78.00 1.03335

79.00 1.01977

80.00 1.00700

81.00 0.99014

82.00 0.97760

83.00 0.96927

84.00 0.95445

85.00 0.94761

86.00 0.93675

87.00 0.93027

88.00 0.92516

89.00 0.92357

90.00 0.92288


My experiance tells me that as the LG''s get shorter the stone gets darker.

I expect you mean the loss is the loss of light return that comes from head extinction / obscuration as the mains get fatter. Of course that would depend on many factors - but as a stab in the dark (punny?) yours is as good as anyothers.

Firey debate indeed. I was just looking at GIA''s Fire Study and they have the complete opposite result. They have a peak at 85% and downhill elsewhere.

 

[Garry H (Cut Nut)]

Here is a series of DiamCalc Disco lighting models of Tolkowsky with 75% table and each with 5 degree tilt. Straight on the fire is even more exaggerated.

Lower facets length ETAS Fire Intensity and Square weighted mono
60.00 1.39745
65.00 1.29338
70.00 1.19306
75.00 1.07788
80.00 1.00350
85.00 0.93908
90.00 0.95544

 

[echelon6]

Date: 7/16/2007 1:56:23 AM
Author: Garry H (Cut Nut)
My experiance tells me that as the LG''s get shorter the stone gets darker.
I expect you mean the loss is the loss of light return that comes from head extinction / obscuration as the mains get fatter. Of course that would depend on many factors - but as a stab in the dark (punny?) yours is as good as anyothers.

Garry, thanks for all the data. And I appreciate all the input from others.

Just on that note, lets say we disregard head obstruction totally. In a lab setting, if I shine, say, 100 watts (measuring light isn''t too tricky I''d imagine, here I use watts) of incandescent light directly into the top of a TIC diamond with LGF=78%, then I get 90 watts back out the top. If I decrease the LGF down to say 70%, would my total light return (disregarding the ratio split between chromatic / white light) fall below 90 watts? all else equal?

I know what you''re trying to say is that: Lower LGF -> Bigger arrows -> Bigger surface area dependant on light coming from high angles -> Diamond more dependant on light from high angles -> Diamond appears darker in practice due to head obstruction. I''m not worried about that, I just want to know whether a lower LGF causes a diamond to be darker for some other cause other than head obstruction.

 

[echelon6]

Oh and another thing on that data, is it possible to also get a data set for white light return? Then after adjusting the data appropriately so they are directly comparable, you can easily add the two curves up, find the maximum point, and voila, a mathematically proven ideal LGF range which produces the maximum sum of colored and white light. Possible?

 

[strmrdr]

Date: 7/16/2007 3:25:42 AM
Author: echelon6
Oh and another thing on that data, is it possible to also get a data set for white light return? Then after adjusting the data appropriately so they are directly comparable, you can easily add the two curves up, find the maximum point, and voila, a mathematically proven ideal LGF range which produces the maximum sum of colored and white light. Possible?

Wont work.
The lighting for max fire and the lighting for max white light will be different.
All you might be able too come up with is the total for one light envirement, move to another and it changes.

 

[Garry H (Cut Nut)]

Date: 7/16/2007 3:22:10 AM
Author: echelon6

I just want to know whether a lower LGF causes a diamond to be darker for some other cause other than head obstruction. It is pretty much all about loss of light return because the diamond is returning more light from the head dierction via the mains. The other amounts of light loss do not kick in until the stone gets steeper deeper and leaks etc

I am just learning about this DC3 software - so I am experimenting here:

Lower facets length Light Return mono ETAS Monochrome Simple mono
60.00 0.98925 0.87470
65.00 1.01771 0.82480
70.00 0.99865 0.92976
75.00 1.01772 1.05621
80.00 1.03005 1.03159
85.00 1.03992 0.90734
90.00 1.05378 1.22893

You can see from the light return mono that there is more brightness with longer lower girdles as you suggested Ech

Now for these fire images I souped up the number of rays and all sorts of other new goodies in the DC toy box.

 

[strmrdr]

When is DC3 due? is it going to be a free update?

 

[Garry H (Cut Nut)]

Within a month, and free for hasp version users Storm (which is you), and the cost of a hasp key for those with a web downloaded reg # version.

But some of the stuff I am doing here will be on a 3.5K pro version.

 

[echelon6]

DC seems like a fun tool to play with.

I plugged those numbers into excel and compared lines of best fit. Didn''t get much meaningful analysis out of it, except that the fire curve is steeper than the white light curve, meaning lower LGF gives more fire for less loss of white light. Hah if only it were that simple...

 

[strmrdr]

Date: 7/16/2007 8:35:36 AM
Author: echelon6
DC seems like a fun tool to play with.

I plugged those numbers into excel and compared lines of best fit. Didn''t get much meaningful analysis out of it, except that the fire curve is steeper than the white light curve, meaning lower LGF gives more fire for less loss of white light. Hah if only it were that simple...

It is a lot of fun to play with.
One thing way kewl about PS is that we are on the cutting edge(pun) of diamond research thanks to having Serg and Garry plus AGS working with the PS vendors and playing indirectly in the sandbox here.

 

[strmrdr]

Date: 7/16/2007 6:50:31 AM
Author: Garry H (Cut Nut)
Within a month, and free for hasp version users Storm (which is you), and the cost of a hasp key for those with a web downloaded reg # version.

But some of the stuff I am doing here will be on a 3.5K pro version.

WAy kewl on it being a free update.
Im assuming that the pro version will be a paid update from the standard?

 

[Cehrabehra]

Date: 7/15/2007 10:24:19 PM
Author: echelon6
Thanks for all the replies, and a big thanks to John Quixote for your detailed input.

Its just that vendors here have previously said that 77-80 makes for an optimal tradeoff between white light / fire, so this leads me to think that the whole LGF issue is one of performance, not merely taste? i.e. I fear that 74 may be suboptimal in terms of the DCLR / brilliance tradeoff.

e.g. to illustrate my point with numbers (I know this is a crude or utterly wrong representation of what actually happens, but it highlights my concerns exactly):

At 77-80, Fire = 40%, White light = 60%, perfectly efficient diamond
At 73-77, Fire = 60%, White light = 30%, loss = 10% somewhat inefficient diamond
At 67.5-73, Fire = 70%, White = 10%, loss = 20% very inefficient

The ''loss'' (im just making terms up here) is not leakage as we understand it, but rather ''loss'' in perception of the diamond''s overall light return? e.g. human eyes might interpret fire / white light differently, and by moving the LGF outside of ideal ranges, it might make a dull-appearing diamond?

Please correct me if I''m wrong.

Where did you get this info? IME the LGF effect the SIZE of the flashes, not the overall light return.

 

[Garry H (Cut Nut)]

Date: 7/16/2007 1:48:13 PM
Author: Cehrabehra

Date: 7/15/2007 10:24:19 PM
Author: echelon6
Thanks for all the replies, and a big thanks to John Quixote for your detailed input.

Its just that vendors here have previously said that 77-80 makes for an optimal tradeoff between white light / fire, so this leads me to think that the whole LGF issue is one of performance, not merely taste? i.e. I fear that 74 may be suboptimal in terms of the DCLR / brilliance tradeoff.

e.g. to illustrate my point with numbers (I know this is a crude or utterly wrong representation of what actually happens, but it highlights my concerns exactly):

At 77-80, Fire = 40%, White light = 60%, perfectly efficient diamond
At 73-77, Fire = 60%, White light = 30%, loss = 10% somewhat inefficient diamond
At 67.5-73, Fire = 70%, White = 10%, loss = 20% very inefficient

The ''loss'' (im just making terms up here) is not leakage as we understand it, but rather ''loss'' in perception of the diamond''s overall light return? e.g. human eyes might interpret fire / white light differently, and by moving the LGF outside of ideal ranges, it might make a dull-appearing diamond?

Please correct me if I''m wrong.

Where did you get this info? IME the LGF effect the SIZE of the flashes, not the overall light return.

Sara Ech is correct - the overall light return does reduce. The numbers / estimates are a bit over done, but the concept is on the $$$$

 

[WinkHPD]

Date: 7/16/2007 3:59:11 PM
Author: Garry H (Cut Nut)

Sara Ech is correct - the overall light return does reduce. The numbers / estimates are a bit over done, but the concept is on the $$$$

I am not at all sure that I agree with that and am looking to get some further information on it. I doubt that the reduction of brilliance, if any, is at all eye visible.

I know that one of the problems with Brilliancescope was its metric of adding up all of the pixels of white light and subtracting the pixels of colored light and thus reducing the brilliance scores of highly dispersive stones. I do not have any idea if they still do that or not, but I do know that the machine was found not to be dependable or acceptable by both GIA and AGS when they were doing their early cut studies.

If it is a matter of one or two percent, I might believe that, but I would not believe that one or two percent is a number that could be perceived by the human eye at the top of the range that is represented by an AGS 0 cut grade stone.

I fear that we are headed into a "let''s scare the consumer into doing what we think is best" area.

I believe that we are talking much more about a taste area than a performance area and that were we able to run accurate numbers we might see a significant increase in the size of the flash visible, and the dispersion that would be visible with either no reduction of brilliance or such minimal reduction of brilliance that the reduction would not be discernable to the human eye.

Just for fun, provided it will print, here is a PGS analysis of the stone listed above, a Tolkowsky with an 80 LGF and the thread stone with the 74LGF changed to an 80 LGF.

Filename Shape FinalGrade Cumulative Brightness Dispersion Contrast Leakage WeightRatio Durability Girdle Culet Tilt Symmetry Polish
pricescope thread 80% lg height.stl Round 0 0 0 0 0 0 0 0 0 0 0 0 0
pricescope thread 74% lg height.stl Round 0 0 0 0 0 0 0 0 0 0 0 0 0
tolkowsky lg80% lg height.stl Round 0 0 0 0 0 0 0 0 0 0 0 0 0
Darn, the spacing got all messed up, but you can see the results In the spread sheet each of the 0''s is below the corresponding colum, brightness dispersion etc.

Hmmm, all three stones got 0''s in every catagory. It''s completely a taste factor in this realm. As such, maybe we can allow that there may be minor, imperceptable differences in brilliance, but major differences in appearance based on the length of the LGF.

The real solution to this is to go see the stones. Buy the one that you like, don''t buy the others. It is OKAY to have preferences, I question that it is okay to attempt to force our preferences on others or to scare anyone that his/her preference is unacceptable.

 

[WinkHPD]

Just a quick follow up for those who are interested in some technical blathering.

Dispersion is only visible to the eye when the length of the dispersive ray is wider than the pupil of the eye when it arrives at the eye. If it is smaller, then the ray will be recombined into white light and no dispersive effect will be seen, while the person standing just a few inches or feet further back may well be amazed at the beautiful dispersion of the stone in question.

Since the shorter lgf results in in broader flashes of light it will also give rise to much broader rays of dispersion and thus more perceptible dispersion, which some people love and others do not. It is my belief, not yet provable by me but I am hoping that it will be someday, that the dispersion may increase by as much as fifteen or more percent with little to no reduction in brilliance, and certainly not any reduction that is visible to they eye. If you ever want to see a dispersion fire event, go look at a well cut Old European Cut with 50% LGF''s. Now there is a stone to make a dispersion lover''s heart happy!

I do know that AGS is working on the software to eventually prove or disprove this, but it is not yet ready for prime time so I can not running to them to solve this for me. I do know that their PGS software likes all three of the stones that were run well enough to give them all the top grade available under that system, and thus I believe very strongly that all three will be incredibly beautiful gems.

Wink

 

[WorkingHardforSmallRewards]

wow, I just got off work, and do I have alot to learn. lol. Can''t wait to eventually get to take some classes and read some good books. But, since I can''t comment on any of the above I was curious, wink, as to what percentage of AGS 0''s actually get all true unrounded 0''s, even in the decimal values.
Did you round off the decimal value deductions to yield those zeros for the AGS 0
Since the AGS zero light return % requirements are broader than 2% wouldn''t some of those decimal values not given in the reports represent changes of greater than 2% in light performance, while still being within the ideal range?

 

[WinkHPD]

Date: 7/16/2007 6:50:46 PM
Author: WorkingHardforSmallRewards
wow, I just got off work, and do I have alot to learn. lol. Can't wait to eventually get to take some classes and read some good books. But, since I can't comment on any of the above I was curious, wink, as to what percentage of AGS 0's actually get all true unrounded 0's, even in the decimal values.
Did you round off the decimal value deductions to yield those zeros for the AGS 0
Since the AGS zero light return % requirements are broader than 2% wouldn't some of those decimal values not given in the reports represent changes of greater than 2% in light performance, while still being within the ideal range?

True unrounded 0's? Have you not heard the news? THEY ARE ALL AGS 0 CUT GRADE DIAMONDS.

Some will prefer the stone with shorter LGF's some will prefer the stone with longer LGF's. I for one am NOT going to get into grading stones by the decimal point and having someone start a thread about this stone is really an AGS 0.489 rather than a 0.012, do you think I should hold out for a 0.012 or better a 0.000 to get a really well cut diamond. I can see the twenty five page debate already.

I wish I thought that was only a distant possibility, but I have been a pricescoper for too long.

Me, "This stone represents less than one tenth of one percent of all diamonds on the market today".

Client, "Well when you find one that represents the very best of the one one thousanth of a percent of one percent, then let me know, I will only settle for the very best."

Me, "But you may not even like that stone as well as one that has some dispersion."

Client, "Then find me one that meets my parameters that is also high on dispersion, surely there is at least one competent cutter in the world who can do that."

Me, "Sigh, please call Fred Cuellar, he can help you."

(Bad inside joke, just ignore it.)

Wink