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Why Does This Good Cut Show Light Leakage?


Mainer
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What seems to be a  well cut round diamond shows light leakage on the AGS-ABET and Ideal Scope images.  If a good cut optimizes reflection and minimizes leakage what has caused this diamond to show leakage?

 

1.667 cts  I  VS2

7.63-7.66/4.67

Table 56.3

Depth 61.2

Crown angle 34.4

Pav angle  40.7

Crown Height 15%

Pav. 42.9%

Star facet 53

Girdle facet 77

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I don't know how to post a picture.  I can move the image to my desk top but I can't find a way to get it onto this page.  

Edited by Mainer
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The easiest way is to link the image onto the site from an image sharing site (Picasa, Photobucket, Facebook, whatever enables you to post an image on the web):

 

You need to copy the photo's URL, which will look something like

 

http://www.diamondsbylauren.com/sc_images/products/2156_thumbnail_image.jpg
You then paste that URL in an IMG tag:

 

[IMG=http://www.diamondsbylauren.com/sc_images/products/2156_thumbnail_image.jpg]
and you get this:

 

2156_thumbnail_image.jpg

 

If you do not have access to an image sharing site, then you can attach the image to the post. Instructions are here: http://www.diamondreview.com/forum/topic/8280-attaching-jig-images/

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post-134026-0-99205100-1425367421_thumb.jpgpost-134026-0-19097400-1425367438_thumb.jpg

 

 

 

 

The ideal scope doesn't show the quantity of pink in the small thumbnail above.  It's actually quite pink 

 

And I don't think I got the right AGS=ABET  images on the left.  Will try again

Edited by Mainer
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post-134026-0-46239300-1425368173_thumb.jpg

 

I enlarged the images to increase the pink.  It shows up a little better here but still not as much as in the original picture

post-134026-0-33734500-1425368229_thumb.jpg

Edited by Mainer
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On the help - you are welcome. BTW, it's ASET (Angular Spectrum Evaluation Tool), not ABET.

 

"Leakage" is actually a fairly ill-defined term. Pretty much all the white there is (i.e. windowing - places where the stone does not reflect light back but allows you to see through it directly), is in places where it's pretty much unavoidable to have it:

 

1. At the junctions of the star facets

2. On the edge of the crown. Actually, this one can be reduced further by tinkering with the kite and upper girdle facet angles, but GIA/AGS tend to penalise (on cut grade) cutters that do that, because it leads to greater weight retention (and thus can be used to cut stones that look smaller than their weight would otherwise imply). I happen to disagree with GIA and AGS on this, but my opinion doesn't count.

 

There is a certain amount of pink spread throughout, indicating partial reflection, and this could be because the cutter was trying to eliminate certain imperfections or because he/she was unable to cut the facet exactly as desired/required (diamonds are tough little buggers, and there may well be a "fight" between getting the right angle and getting the facet polished properly). It is at least as likely - if not more - that the leakage is an artefact of the photo; all it takes is a diamond that is 0.1 mm too low relative to the correct position, and white will start showing where it shouldn't  (equally, 0.1 mm "too high" and suddenly there is plenty of red even in windows).

 

The only way of resolving this one is to see the diamond. Personally, I doubt very much you'd be able to see any decrease of brightness in the pink areas - not least because the cutter seems to have taken his/her time and not be unduly concerned with weight saving (definitely not trying to hit a weight threshold, at 1.667).

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It is at least as likely - if not more - that the leakage is an artefact of the photo; all it takes is a diamond that is 0.1 mm too low relative to the correct position, and white will start showing where it shouldn't  (equally, 0.1 mm "too high" and suddenly there is plenty of red even in windows).

  

I don't know... both are a definite possibility. As I said above, 0.1 mm depth "in" or "out" of the ASET viewer on a 7 mm stone means 1° difference on angles in the pavilion, and we all know that's enough to throw things out of kilter completely.

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