Light performance picture?

[hejests]

Hey folks. This is my first post and I''d like to thank everyone for the great info I''ve been able to find on here through searches.

I just had the D SI-1 (round 1.02 carats) I picked up for my sweetheart''s engagement ring independantly graded (I''m in Toronto and didn''t trust gemscan''s pre-certs after reading some not so great opinions so I had it graded at Harold Weinstein. Everything was pretty much the same except the D color gemscan gave became an E color at Weinstein''s). Anyhow, Harold Weinstein included a Light Performance image on the grading report. I know that the more red the better, but I don''t really understand enough about the image to know what sort of light performance this diamond has. Anyone know how to read these things? I''ve attached a pic.

Also, you can see the diamond has three feather inclusions close to each other with one of them going out to the edge of the diamond. The diamond''s totally eyeclean (as far as my eyes could see) but I''m wondering if there''s any special care that needs to be given to that end of the diamond with that feather that goes out to the surface? Is that going to cause a problem?

Your help is much appreciated!

Serge

 

[astraea]

I''ll let someone else analyze the light, but my first thought with the inclusion close to the edge is to make sure the diamond is in a secure prong setting to reduce the likelihood of chipping. (Perhaps a six prong setting might be better than a four? I think both of those classic settings are equally beautiful in their own right.) But, I''d definitely get the opinion of an expert over that. I''m curious as well.

 

[Richard Sherwood]

Serge, can you tell us what the statistics are on the cut, so we can correlate it with the image shown?

Total depth percentage.
Table size.
Crown height and angle.
Pavilion depth and angle.
Girdle thickness.
Symmetry.

 

[hejests]

Richard,

Here''s everything I have from the grading report...

Depth: 61.9%
Table: 57.2%
Girdle: Medium, faceted
Culet: none
Crown Depth: 15.0%
Pavilion Depth: 44.1%

Polish & Symmetry both Very Good
Fluorescence: None
Cutting Grade: 1 (Excellent)

(6.71-6.78 x 4.25mm)

Thank you!

Serge

 

[Rhino]

The lack of blues and amount of greens would concern me. Lack of blues isn''t always an issue but the amount of greens concern me more as I view that image.

 

[JulieN]

I found some early ASET threads, 2005/2006:

https://www.pricescope.com/community/threads/aset-photos-and-discussion.38354/

https://www.pricescope.com/community/threads/ags-desktop-aset-images.36480/

Seems to suggest an average looking stone.

 

[hejests]

Thanks Rhino. Do you know what kind of picture it is? (what it''s called). Perhaps I can find a set to compare to online (for an apples to apples comparisson). At the moment, I wouldn''t know what to search for.

What do the blues and greens represent?

Thanks!

Serge

 

[Garry H (Cut Nut)]

Date: 9/12/2008 12:22:23 AM
Author: hejests
Thanks Rhino. Do you know what kind of picture it is? (what it''s called). Perhaps I can find a set to compare to online (for an apples to apples comparisson). At the moment, I wouldn''t know what to search for.

What do the blues and greens represent?

Thanks!

Serge

I am not Rhino, but i too have a thick skin.
It appears to be a very badly taken ASET.

It should be better than average, but not a stella looking stone I think.
The inclusion looks good - pop it under a prong, but make sure the setter knows it is there.

 

[Rhino]

No prob. You may want to check out the threads Julie gave you above but in a nutshell ...

The image is an ASET image. ASET is the abbreviation for "Angular Spectrum Evaluation Tool". ASET imagery primarly shows where the crown of the diamond is drawing its reflections from regarding the atmosphere before it (ie. the angular spectrum). Green represents light entering from a 0 - 45 degree angular spectrum, or the horizon, generally one of the most ineffective sources of illumination.

Pink/Red represents light entering from a 45-75 degree angular spectrum, generally from above where most sources of bright illumination exist

while blue represents a very narrow 75-90 degree angular spectrum representing head/body shadow. When a diamond is drawing the majority of its reflections from above (the 45-75 degree zone) a nice balance of dark reflections intermingled with the bright reflections causes a contrast pattern of darks and lights. While head/body shadow produces contrast that can be positive, too much of it however can be negative as too much head/body reflection within the diamond is not good either. We happen to be poor sources of illumination too.

A layman's example of positive contrast would be to view a checkerboard pattern of evenly distributed black adn white squares. A negative contrast pattern would be to have too many black squares over the amount of bright ones with a poor distribution.

An ASET image is a good piece of information to acquire regarding light performance but it is not an end-all/be-all tool. It has its advantages as well as its weaknesses like most technologies.

Hope that helps.