Discussion of green in an ASET image

[Rockdiamond]

Yoram- the stone is an N color- so it's possible the larger, bottom piece was a light yellow ( maybe U-V, W-X for example).
It's super strong blue fluorescence, which makes it look whiter- but it's fairly yellow in person. I believe the cutter ( who is indeed very skilled in such stones) was going for a light yellow
I'll get some more shots and post them later

ccl- from what I can tell, the simulations are lacking due to the number of bounces.
Theoretically, plotting out and simulating a stone with 5 bounces in reality is a lot easier than doing so with something like a crushed ice stone where the number of bounces must be impossible to accurately calculate.
Even a small tilt will change the number of bounces significantly.
Is it possible that the bounces are what's throwing off the simulation?

 

[ChunkyCushionLover]

Yoram- the stone is an N color- so it's possible the larger, bottom piece was a light yellow ( maybe U-V, W-X for example).
It's super strong blue fluorescence, which makes it look whiter- but it's fairly yellow in person. I believe the cutter ( who is indeed very skilled in such stones) was going for a light yellow
I'll get some more shots and post them later

ccl- from what I can tell, the simulations are lacking due to the number of bounces.
Theoretically, plotting out and simulating a stone with 5 bounces in reality is a lot easier than doing so with something like a crushed ice stone where the number of bounces must be impossible to accurately calculate.
Even a small tilt will change the number of bounces significantly.
Is it possible that the bounces are what's throwing off the simulation?

RD,

It would appear 10 bounces and up is pretty close IMO.

 

[Karl_K]

Here I have used Garry's Lightbox lighting scheme with built in Observer and Camera.
I also took a photograph of a Red Envelope to use as a background so that we could easily separate leakage from Obstruction.

Red areas are of leakage, darker areas are reflecting dark objects.

As can be seen the virtual facet pattern becomes much more broken up when the number of bounces is increased.
Its easier to see the difference between the two in this lighting.

more bounces is helping.
Can you post the dmc file you are using so I can post something and be on the same page?

 

[ChunkyCushionLover]

I sent you e-mail, will send you the files but they are too large to attach here on in email.

 

[Karl_K]

Here is what I am talking about, the point the arrow points to lights up if it is in a dark zone secondary VF.
There is no way you would get 100% reflection at that point. In an RB/EC/SE you would normally never see it because of the higher contrast except at large tilts in a weaker light return EC/SE where I have also noticed it.
I noticed the effect in a crushed ice radiant diamond where areas appeared to glow but when you looked closer they were in a dark secondary virtual facet.

 

[ChunkyCushionLover]

Here is what I am talking about, the point the arrow points to lights up if it is in a dark zone secondary VF.
There is no way you would get 100% reflection at that point. In an RB/EC/SE you would normally never see it because of the higher contrast except at large tilts in a weaker light return EC/SE where I have also noticed it.
I noticed the effect in a crushed ice radiant diamond where areas appeared to glow but when you looked closer they were in a dark secondary virtual facet.

Why not? The angle of incidence to the normal of the table looks to be well above the critical angle.

 

[Garry H (Cut Nut)]

Here is what I am talking about, the point the arrow points to lights up if it is in a dark zone secondary VF.
There is no way you would get 100% reflection at that point. In an RB/EC/SE you would normally never see it because of the higher contrast except at large tilts in a weaker light return EC/SE where I have also noticed it.
I noticed the effect in a crushed ice radiant diamond where areas appeared to glow but when you looked closer they were in a dark secondary virtual facet.

Why not? The angle of incidence to the normal of the table looks to be well above the critical angle.

The idea is feasible if the polish is not 100% flat Karl.

Janak has long insisted that one benefit from very high polish is that inclusions appear smaller because of fresnel magnification.
(like the sheets of plastic from stationary stores that work as magnifyer's)

 

[ChunkyCushionLover]

Garry,

Lets assume the polish isn't flat, it could change the refractive index down by X or the normal of the table plain by Y. X and Y are very small and would both serve to raise the critical angle by a bit. I still don't know how this causes anything significant. Especially in diamonds with very good or excellent polish and symmetry.

Please explain guys.

 

[Garry H (Cut Nut)]

Think groves in a vinyl record CCL

 

[Rockdiamond]

Yoram- the stone is an N color- so it's possible the larger, bottom piece was a light yellow ( maybe U-V, W-X for example).
It's super strong blue fluorescence, which makes it look whiter- but it's fairly yellow in person. I believe the cutter ( who is indeed very skilled in such stones) was going for a light yellow
I'll get some more shots and post them later

ccl- from what I can tell, the simulations are lacking due to the number of bounces.
Theoretically, plotting out and simulating a stone with 5 bounces in reality is a lot easier than doing so with something like a crushed ice stone where the number of bounces must be impossible to accurately calculate.
Even a small tilt will change the number of bounces significantly.
Is it possible that the bounces are what's throwing off the simulation?

RD,

It would appear 10 bounces and up is pretty close IMO.

I think we're getting a lot closer ccl- they all have a likeness, but I think the 50 bounce version looks the best.
One question- there's a "reflection" across the top of the diamond, as if the light source is coming from that direction- can we get rid of that?

 

[Karl_K]

Garry,

Lets assume the polish isn't flat, it could change the refractive index down by X or the normal of the table plain by Y. X and Y are very small and would both serve to raise the critical angle by a bit. I still don't know how this causes anything significant. Especially in diamonds with very good or excellent polish and symmetry.

Please explain guys.

While called ID/EX polish it is actualy very much flawed compared to say a hand tuned mirror.
The hardness of the material and the grain structure prevent anything close to a theoretical perfect polish.
I was actually appalled at EX polish the first time I looked at the surface at 100x-200x.
Remember it is graded at 10x if it isn't visible at 10x it doesn't exist as far as diamond polish grading goes.
No facet is ever really flat either, the table and other large facets in particular.

 

[ChunkyCushionLover]

Garry,

Lets assume the polish isn't flat, it could change the refractive index down by X or the normal of the table plain by Y. X and Y are very small and would both serve to raise the critical angle by a bit. I still don't know how this causes anything significant. Especially in diamonds with very good or excellent polish and symmetry.

Please explain guys.

While called ID/EX polish it is actualy very much flawed compared to say a hand tuned mirror.
The hardness of the material and the grain structure prevent anything close to a theoretical perfect polish.
I was actually appalled at EX polish the first time I looked at the surface at 100x-200x.
Remember it is graded at 10x if it isn't visible at 10x it doesn't exist as far as diamond polish grading goes.
No facet is ever really flat either, the table and other large facets in particular.

Karl,

I have no trouble visualizing some minor impact from polish or non flat facets or lack thereof but I deem this point to be minor and I think it would be a mistake to claim this as a major contributor to deviations between theoretical and actual. The lighting and intensity estimations have a much greater impact on potential differences.

 

[Garry H (Cut Nut)]

Garry,

Lets assume the polish isn't flat, it could change the refractive index down by X or the normal of the table plain by Y. X and Y are very small and would both serve to raise the critical angle by a bit. I still don't know how this causes anything significant. Especially in diamonds with very good or excellent polish and symmetry.

Please explain guys.

While called ID/EX polish it is actualy very much flawed compared to say a hand tuned mirror.
The hardness of the material and the grain structure prevent anything close to a theoretical perfect polish.
I was actually appalled at EX polish the first time I looked at the surface at 100x-200x.
Remember it is graded at 10x if it isn't visible at 10x it doesn't exist as far as diamond polish grading goes.
No facet is ever really flat either, the table and other large facets in particular.

Karl,

I have no trouble visualizing some minor impact from polish or non flat facets or lack thereof but I deem this point to be minor and I think it would be a mistake to claim this as a major contributor to deviations between theoretical and actual. The lighting and intensity estimations have a much greater impact on potential differences.

Polishers use Avalon or similar tools to check the polish in production lines (pun) and it appears the surface is often 'grooved' which would definitely have an impact that will increase as the number of internal bounces rises.
http://www.wtocd.be/Solutions/Avalon.html http://www.lexus-com.com/lexusnew/Product/Productd/Grading/Avalon.htm

Perhaps the stone would even heat up a bit more, and then we cant call them crushed ice?

 

[Karl_K]

Karl,

I have no trouble visualizing some minor impact from polish or non flat facets or lack thereof but I deem this point to be minor and I think it would be a mistake to claim this as a major contributor to deviations between theoretical and actual. The lighting and intensity estimations have a much greater impact on potential differences.

ccl there are huge holes in virtual technology once you get past the simple and well researched.
RB can be modeled very very very well, some step cuts can also but some of them give minor unexpected results but all bets are off on very complex cuts. We can get close enough to tell if a design has merit but it will have to be vetted by actually cutting them.
In an RB these minor variations are not a huge deal but that does not mean they arent on more complex models/cuts.
Once they are cut we can go back and refine our virtual parameters and look for missing links.

 

[Garry H (Cut Nut)]

Karl,

I have no trouble visualizing some minor impact from polish or non flat facets or lack thereof but I deem this point to be minor and I think it would be a mistake to claim this as a major contributor to deviations between theoretical and actual. The lighting and intensity estimations have a much greater impact on potential differences.

ccl there are huge holes in virtual technology once you get past the simple and well researched.
RB can be modeled very very very well, some step cuts can also but some of them give minor unexpected results but all bets are off on very complex cuts. We can get close enough to tell if a design has merit but it will have to be vetted by actually cutting them.
In an RB these minor variations are not a huge deal but that does not mean they arent on more complex models/cuts.
Once they are cut we can go back and refine our virtual parameters and look for missing links.

I have never used the polish dissipation slider on the polish quality under lighting parameters in DiamCalc. Just tried and it does not slide - but I know it did at some stage. Perhaps I will ask Sergey about it.

 

[ChunkyCushionLover]

Karl,

I have no trouble visualizing some minor impact from polish or non flat facets or lack thereof but I deem this point to be minor and I think it would be a mistake to claim this as a major contributor to deviations between theoretical and actual. The lighting and intensity estimations have a much greater impact on potential differences.

ccl there are huge holes in virtual technology once you get past the simple and well researched.
RB can be modeled very very very well, some step cuts can also but some of them give minor unexpected results but all bets are off on very complex cuts. We can get close enough to tell if a design has merit but it will have to be vetted by actually cutting them.
In an RB these minor variations are not a huge deal but that does not mean they arent on more complex models/cuts.
Once they are cut we can go back and refine our virtual parameters and look for missing links.

Karl,

Very vague and general statement.

Any examples Karl?
Do you have any examples of brilliant cuts that cannot be handled by DC?

 

[ChunkyCushionLover]

Garry,

Lets assume the polish isn't flat, it could change the refractive index down by X or the normal of the table plain by Y. X and Y are very small and would both serve to raise the critical angle by a bit. I still don't know how this causes anything significant. Especially in diamonds with very good or excellent polish and symmetry.

Polishers use Avalon or similar tools to check the polish in production lines (pun) and it appears the surface is often 'grooved' which would definitely have an impact that will increase as the number of internal bounces rises.
http://www.wtocd.be/Solutions/Avalon.html http://www.lexus-com.com/lexusnew/Product/Productd/Grading/Avalon.htm

Perhaps the stone would even heat up a bit more, and then we cant call them crushed ice?

Gary,

The internal surface is still diamond. How much of a realistic impact (in % terms) and in what way?
This is all extremely vague, unexplained, and no examples given.

 

[Garry H (Cut Nut)]

Its not that hard CCL.
Fancy cuts are harder to get a great polish on facets - especially those close to octahedral plane. Lots of internal bounces at lower angles of incidence = more chance for a few deviant rays to emerge in the wrong place = even more crushed ice effect.

 

[ChunkyCushionLover]

Its not that hard CCL.
Fancy cuts are harder to get a great polish on facets - especially those close to octahedral plane. Lots of internal bounces at lower angles of incidence = more chance for a few deviant rays to emerge in the wrong place = even more crushed ice effect.

You are right Garry it isn't that hard to post two lines explaining how much you know instead of explaining in detail the point you are trying to make.

Your last few posts in this thread serve little benefit to me as they lack context, example and proof.

 

[Garry H (Cut Nut)]

Its not that hard CCL.
Fancy cuts are harder to get a great polish on facets - especially those close to octahedral plane. Lots of internal bounces at lower angles of incidence = more chance for a few deviant rays to emerge in the wrong place = even more crushed ice effect.

You are right Garry it isn't that hard to post two lines explaining how much you know instead of explaining in detail the point you are trying to make.

Your last few posts in this thread serve little benefit to me as they lack context, example and proof.

I have no proof CCL, not offering proof, just postulating why it might be possible for something to happen which I think Karl too is suggesting might be an effect, not IS an actual event.

 

[Karl_K]

Its not that hard CCL.
Fancy cuts are harder to get a great polish on facets - especially those close to octahedral plane. Lots of internal bounces at lower angles of incidence = more chance for a few deviant rays to emerge in the wrong place = even more crushed ice effect.

You are right Garry it isn't that hard to post two lines explaining how much you know instead of explaining in detail the point you are trying to make.

Your last few posts in this thread serve little benefit to me as they lack context, example and proof.

I have no proof CCL, not offering proof, just postulating why it might be possible for something to happen which I think Karl too is suggesting might be an effect, not IS an actual event.

yep


as far as facet flatness and symmetry and polish quality a few minutes with a high power scope and you would see for yourself.
Or talk to someone who cuts them.

 

[Karl_K]

Karl,

I have no trouble visualizing some minor impact from polish or non flat facets or lack thereof but I deem this point to be minor and I think it would be a mistake to claim this as a major contributor to deviations between theoretical and actual. The lighting and intensity estimations have a much greater impact on potential differences.

ccl there are huge holes in virtual technology once you get past the simple and well researched.
RB can be modeled very very very well, some step cuts can also but some of them give minor unexpected results but all bets are off on very complex cuts. We can get close enough to tell if a design has merit but it will have to be vetted by actually cutting them.
In an RB these minor variations are not a huge deal but that does not mean they arent on more complex models/cuts.
Once they are cut we can go back and refine our virtual parameters and look for missing links.

Karl,

Very vague and general statement.

Any examples Karl?
Do you have any examples of brilliant cuts that cannot be handled by DC?

vague and general but very true.

not for public consumption.

It is not a matter of handling them it is a matter of the default assumptions and interpretations based on other cuts being accurate for a new cut.
For example double reflection maps are enough for a RB most SE/EC but not crushed ice.

 

[ChunkyCushionLover]

Karl,

I have no trouble visualizing some minor impact from polish or non flat facets or lack thereof but I deem this point to be minor and I think it would be a mistake to claim this as a major contributor to deviations between theoretical and actual. The lighting and intensity estimations have a much greater impact on potential differences.

ccl there are huge holes in virtual technology once you get past the simple and well researched.
RB can be modeled very very very well, some step cuts can also but some of them give minor unexpected results but all bets are off on very complex cuts. We can get close enough to tell if a design has merit but it will have to be vetted by actually cutting them.
In an RB these minor variations are not a huge deal but that does not mean they arent on more complex models/cuts.
Once they are cut we can go back and refine our virtual parameters and look for missing links.

Karl,

Very vague and general statement.

Any examples Karl?
Do you have any examples of brilliant cuts that cannot be handled by DC?

vague and general but very true.

not for public consumption.

It is not a matter of handling them it is a matter of the default assumptions and interpretations based on other cuts being accurate for a new cut.
For example double reflection maps are enough for a RB most SE/EC but not crushed ice.

Karl,

It is my general impression that your theory seems plausible and would have a greater effect in stones with more bounces off the crown and longer light paths.

However I really question the magnitude and significance of the deviations caused by this and without example(s) it remains unproven.

Would you like the take home message for those casually reading this to be "throw out simulations as being inaccurate for longer light path diamonds?"

I don't think that is the case here.

 

[Karl_K]

not:
"throw out simulations as being inaccurate for longer light path diamonds?"

but this:
Care must be taken when interpreting simulations and some parameters may need to be adjusted(more bounces, possibility of areas being lighted by bounced rays) when dealing with longer light path diamonds.

 

[Garry H (Cut Nut)]

bump re https://www.pricescope.com/communit...real-life.203965/page-5#post-3716973#p3716973