Table Brightness in the AGS Lab Report

[fayya]

Hi, I have a question about the light performance map being shown in the AGS Lab Report.

Comparing the following 2 reports, you can see #2 has green (less bright) showing at the table, and #1 has full red, does it mean #1 has better reflection at the table or should I care about that?

#1
http://www.briangavindiamonds.com/diamonds/diamond-details/1.227-h-vs1-round-diamond-ags-104067041005#!prettyPhoto[gallery2]/3/

#2
http://www.briangavindiamonds.com/diamonds/diamond-details/1.228-g-si1-round-diamond-ags-104064813022#!prettyPhoto[gallery2]/2/

Thanks in advance!

 

[fayya]

no one?

 

[c-k]

I believe the answer to your question is no.

If I remember correctly it has to do with the pavilion angle, have seen red, green & red/green. The experts will have to explain at what angles the color changes and why.

 

[insured]

I believe the answer to your question is no.

If I remember correctly it has to do with the pavilion angle, have seen red, green & red/green. The experts will have to explain at what angles the color changes and why.

I looked into this recently and this is the same as what I was told - there's an ASET table somewhere, and right in the middle of ideal range pav angles it switches from red to green but I was told it should not have significant effect on appearance of the diamond. Experts with far more viewing experience than me may weigh in otherwise.

 

[WinkHPD]

Hi, I have a question about the light performance map being shown in the AGS Lab Report.

Comparing the following 2 reports, you can see #2 has green (less bright) showing at the table, and #1 has full red, does it mean #1 has better reflection at the table or should I care about that?

#1
http://www.briangavindiamonds.com/diamonds/diamond-details/1.227-h-vs1-round-diamond-ags-104067041005#!prettyPhoto[gallery2]/3/

#2
http://www.briangavindiamonds.com/diamonds/diamond-details/1.228-g-si1-round-diamond-ags-104064813022#!prettyPhoto[gallery2]/2/

Thanks in advance!

The change from the green dot to the solid red in the ASET occurs at a specific pavilion angle that Peter Yantzer, the Executive Director of the American Gem Society Laboratoy, told me way back when during the ASET research and development days and which, since I did not write it down I have forgotten. Apparently it is somewhere between 40.8 and 40.9 since that is the angle of these two stones, with one of them solid red and the other with the green dot. Occasionally you will see a stone with a mixed red and green center in which some of the pavilion main facets are above and others below that magic angle.

He also told me not to get too into worrying about it since the green actually increased the contrast in the center of the stone by a little tiny bit, and contrast is one of the factors that we are hard wired to detect and appreciate. (When we were hunter gatherers, the ability to detect contrast and edges often made the difference between spotting game and coming home with food or not spotting game and going hungry. If you consistently went hungry, eventually your genes were removed from the pool, perhaps from not detecting one of the predators that were also trying not to be hungry...)

Basically you should not spend any time worrying about it, but if you think you might like one or both of these diamonds you should arrange to see it, or if possible, them to see which your eyes like better.

Wink

 

[Garry H (Cut Nut)]

The answer is that at exactly 40.75 degrees the light entering perpendicular to the table exits at exactly 45 degrees (and vice a versa) and there fore angles steeper hit the red ASET zone and shallower hit the green.
The difference is negligible.

 

[WinkHPD]

The answer is that at exactly 40.75 degrees the light entering perpendicular to the table exits at exactly 45 degrees (and vice a versa) and there fore angles steeper hit the red ASET zone and shallower hit the green.
The difference is negligible.

Garry,

I agree that the difference is negligible, but now you have peaked my interest.

If the transition is exactly 40.75 degrees, then why is it that the above mentioned diamond with the 40.8 degree pavilion angle is showing green instead of the red that you say it should be showing???

Here is the link again for your viewing pleasure: http://www.briangavindiamonds.com/diamonds/diamond-details/1.228-g-si1-round-diamond-ags-104064813022#!prettyPhoto[gallery2]/3/

Wink

 

[c-k]

The answer is that at exactly 40.75 degrees the light entering perpendicular to the table exits at exactly 45 degrees (and vice a versa) and there fore angles steeper hit the red ASET zone and shallower hit the green.
The difference is negligible.

Garry,

I agree that the difference is negligible, but now you have peaked my interest.

If the transition is exactly 40.75 degrees, then why is it that the above mentioned diamond with the 40.8 degree pavilion angle is showing green instead of the red that you say it should be showing???

Here is the link again for your viewing pleasure: http://www.briangavindiamonds.com/diamonds/diamond-details/1.228-g-si1-round-diamond-ags-104064813022#!prettyPhoto[gallery2]/3/

Wink

My understanding is that within that very diamond although the pavilion averages at 40.8 there are more angles at or below the 40.75 to turn the ASET green. So maybe in a stone where there is a 50/50 above & below you have the green/red combo???