confusion about shallow diamonds

[Lula]

Date: 3/23/2010 5:31:34 PM
Author: Rockdiamond
You're welcome Sara!!


in thew photo above the stone on the left has a shallower crown, and larger table- which has relevance to this discussion

We can see a more defined pattern in the stone on the right- however I prefer the lack of that pattern...



The entire conversation is here

And I prefer the crisp on-off contrast of the one on the right (as you know!)

But there are many people who prefer the brightness and splintery flash of stones with lower crowns, bigger tables, and longer lgf's, so I think discussions like this are valuable so that we can better help consumers choose stones to match their personal preferences.

I do think it has been demonstrated that there are optimal cut parameters for each "style" of stone, and simply selecting a stone for its low crown angle and large table without examining the stone further is not advised. At least that's what I'm getting from this discussion -- correct me if I'm wrong.

 

[Stephan]

Hi Sara,
A diamond can have a crown with an angle shallower than pricescope standards without needing a huge table or long lower girdles.

 

[Rockdiamond]

Thank you Sara- I so much appreciate your willingness to consider alternative views.

Another interesting aspect to the photo is the fact that the stone on the left looks larger. This was also true in person.

In fact, the larger tabled stone on the left measures 5.25mm at it''s largest, versus 5.27 for the stone on the right.

This again goes to the potential advantages of a shallower stone.

 

[Rockdiamond]

Stephan, the table on the stone on the left was 61%- not exactly "huge"

 

[Stephan]

Hi David,
I wasn''t criticizing your diamond, I was just saying that a shallower than Tolk is possible with a smaller table and even with broader arrows.

 

[Karl_K]

Date: 3/23/2010 5:53:56 PM
Author: QueenMum
Hi David,

I wasn''t criticizing your diamond, I was just saying that a shallower than Tolk is possible with a smaller table and even with broader arrows.

not exactly....
The broader arrows is problematic....

 

[Karl_K]

The problems with these images:
The top 2 images show head obstruction not light return.
The bottom left is not correct, most shallow RB diamonds obstruction is the problem and has to be really really shallow before they start to leak.
steep/Deep diamonds leak is correct unless they have very short lgf%.
http://journal.pricescope.com/Articles/68/1/Do-the-pavilion-mains-drive-light-return-in-the-modern-round-brilliant.aspx

 

[Stephan]

Date: 3/23/2010 6:08:51 PM
Author: Karl_K
not exactly....
The broader arrows is problematic....

For example:
Table 55
Depth 60.7
Crown 33.5
Pavilion 40.8
Stars 55
Lower girdle 75
What would be the problem?

 

[Karl_K]

20 degree crown 40 degree pavilion, no leakage...

 

[Karl_K]

20 degree crown 35 degree pavilion ah finally it is leaking...

 

[Karl_K]

even at 20/35 it does not leak like in the image....

 

[Karl_K]

Date: 3/23/2010 6:16:28 PM
Author: QueenMum

Date: 3/23/2010 6:08:51 PM

Author: Karl_K

not exactly....

The broader arrows is problematic....

For example:

Table 55

Depth 60.7

Crown 33.5

Pavilion 40.8

Stars 55

Lower girdle 75

What would be the problem?

That isn't shallow if cut right it can get ags0
If it didn't the hit would be in dispersion bumping it to a 1.

 

[Stephan]

Table 55
Depth 60.2
crown 32
pavilion 41
star 55
pavilion 75
is another example.

I know it is not shallow, but I don''t know why some pricescopers think they are inferior to typical H&A.

 

[Rockdiamond]

Karl- I have raised a point about the fact that the the graphic Kenny posted has unrealistic lighting - ie, a single light beam entering the diamond.
How does the software you use to show the simulated diamonds handle that- and what's your feeling about simulations versus real world lighting?


Stephan- I never thought you were criticizing the diamond- I share your question- and have for many many years.

 

[Stephan]

Date: 3/23/2010 6:27:56 PM
Author: Karl_K
That isn''t shallow if cut right it can get ags0
If it didn''t the hit would be in dispersion bumping it to a 1.

I don''t know how AGS measures dispersion.
As I said in many other topics, it doesn''t help a lot to know the size/amount of the fire flashes when you ignore the flare/intensity.

 

[Karl_K]

Date: 3/23/2010 6:37:24 PM
Author: Rockdiamond
Karl- I have raised a point about the fact that the the graphic Kenny posted has unrealistic lighting - ie, a single light beam entering the diamond.

How does the software you use to show the simulated diamonds handle that- and what''s your feeling about simulations versus real world lighting?



Stephan- I never thought you were criticizing the diamond- I share your question- and have for many many years.

David,
If I could cut a diamond like the above absolutely perfectly the DC images in the same real world lighting could not be told from the real thing in some of the lighting.
Others in there are unrealistic to the real world.
DC aset has higher resolution than real world aset.
My guess is that some secondary reflections and or optic problems are not accounted for in DC.
DC IS and real world IS are very close with the virtual images again having higher resolution, this is due mostly to optics.

 

[Lula]

Date: 3/23/2010 5:47:52 PM
Author: QueenMum
Hi Sara,

A diamond can have a crown with an angle shallower than pricescope standards without needing a huge table or long lower girdles.

Yup, I don''t know a lot about stones with shallow crown angles -- gotta learn something new on PS today!

 

[Rockdiamond]

Thanks Karl- is it also accurate to say that real world IS is limiting the light from many angles?

In your opinion, how important are secondary reflections, as well as dramatically wider real world lighting sources in assessing light return?
Follow up- how are these multiple sources of light accounted for in tools that measure light return?

 

[Karl_K]

Date: 3/23/2010 6:39:01 PM
Author: QueenMum

Date: 3/23/2010 6:27:56 PM

Author: Karl_K

That isn''t shallow if cut right it can get ags0

If it didn''t the hit would be in dispersion bumping it to a 1.

I don''t know how AGS measures dispersion.

As I said in many other topics, it doesn''t help a lot to know the size/amount of the fire flashes when you ignore the flare/intensity.

here is the list of what the grade is based on.
It will not show anything but 0 unless it is outside the range.
IE: 0 is a range not a number.

 

[Karl_K]

Date: 3/23/2010 6:51:25 PM
Author: Rockdiamond
Thanks Karl- is it also accurate to say that real world IS is limiting the light from many angles?

I dont understand this question. clarify please?

In your opinion, how important are secondary reflections, as well as dramatically wider real world lighting sources in assessing light return?
they are a consideration because secondary reflections can become primary in some lighting conditions. This is more of a design problem and a problem with fancies than RB''s
Follow up- how are these multiple sources of light accounted for in tools that measure light return?

Different tools work in different ways.
They are ignored in IS and ASET somewhat shows them.
I use simulated Marty type lighting.

 

[Karl_K]

I also use modified ASET with red changed to black.