Green Or Red In The Middle of ASET Image?

I was looking through some AGS ideal cut diamonds online and noticed something peculiar about the AGSL Computer Generated Light Performance Map. In some grading reports, some of the diagrams showed a green circle in the middle of the diamond and on some others, I noticed they were red.

green table reflection vs red table reflection

Green or red center in a round brilliant cut diamond? Which is better?

Based on the articles I read on your website on the ASET images, my takeaway is that we should see as much red as possible. My question is, since the amounts of red would affect light return, shouldn’t the diamond with the green center be graded with a lower cut grade? 

In all of these examples, AGS has graded all of them as triple 0s. Shouldn’t they look identical? If so, why do they apparently have different light performances?


Answer: The circular center that you are referring to is actually caused by the reflection of the table facet on the pavilion facets. The size of the table reflection is determined largely by the table size % and the pavilion depth %.

diamonds with different table sizes

Diamonds with 60.2%, 54.4% and 69.0% table sizes

Technically speaking, the table reflection does not indicate light return or performance since it is a phenomenon caused by reflections in the diamond. Typically, a green reflection is caused by pavilion angles of less than 40.7°.

The center could appear red, green or even as a mixture of both and that’s still fine. In the case of both triple 0s ideal cut diamonds that you had chosen, the color of the table reflections in ASET images won’t impact the physical brilliance or outlook of the stones.

For consumers who are looking for the finest cut diamonds and will settle for nothing less than ideal optics, I recommend checking out Whiteflash and Brian Gavin. Their signature diamonds are polished to extreme precision and hand-picked for the best optical performance.

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2 Comments

  1. Stephen-
    December 4, 2012 at 3:21 pm

    Is there any recommended proportions for selecting great looking round diamonds?

  2. Paul-
    December 14, 2012 at 4:25 am

    You might want to check out my recommended table of proportions for ideal cut rounds here.

    https://beyond4cs.com/shapes/round/ideal-proportions/

    In my experience, when round diamonds come within these proportions, they tend to be of a superior cut quality.

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