How does one assess light return in step cut stones?

[bgray]

I have an emerald cut that I am very pleased with but I was wondering how these stones are graded visually. Unlike rounds for which there is more of a formula for "perfection."

 

[Lorelei]

You will probably find these articles by strmrider useful

http://journal.pricescope.com/Articles/61/1/Virtual-Facets-and-patterns%2c-a-Discussion-about-step-cuts-.aspx

http://journal.pricescope.com/Articles/60/1/Performance-and-the-p3-facets%2c-a-discussion-about-step-cut-diamonds.aspx

 

[Rhino]

Assessing optics in emerald cuts or any cut is a matter of familiarizing yourself with the cutting features that contribute to a deterioration of the appearance and particularly in lighting conditions that would be most common to the viewing public.

In the case of emerald cuts they will generally suffer from one of 2 adverse effects. Excessive light leakage will result in a glassy, grayish, watery appearance (not bright) allowing the viewer to virtually see through the diamond. Too much head/body obstruction will cause an overdarkness which can be common in emerald cuts and is similar to the bowtie effect seen in other fancies.

What I personally like to see is a predominant brightness off the facets without too much of the above. A certain amount of light leakage is not bad because it can add positive contrast to the emerald cut and at the same time a balanced distribution of head/body reflection can accomplish the same.

The trickiest thing is correlating ASET imagery (which is helpful in this exam) with the actual optics and how that translates to human observation. ASET is very helpful but not always 100% conclusive.

 

[strmrdr]

by eye by someone who knows what to look for is best.
When buying remotely video is very helpful.