question for experts re lighting, cut and asets

[nyquestioner]

It is my understanding that when people on here talk about "light performance," they are referring to how a diamond performs under overhead lighting. When people talk about a "good ASET" they are again talking about overhead lighting.

I've noticed that in my own or others' apartments, where lighting tends to be from chandeliers and lamps, my OEC often outsparkles my friends' well-cut MRBs. Which leads me to two questions:

1) When evaluating which diamond will "perform" the best, should one consider what kind of lighting one typically encounters? E.g., if it's usually from lamplight coming at a side-angle, could superideals not be so superideal? Would some leakage on an ASET actually predict better performance?

2) Similarly, should one be looking for the opposite of what one looks for in a ring when evaluating stones for pendants or earrings, since the light angle would be different? E.g., if light is mostly from the side, then ideal cut would be better, but if mostly overhead, then a "leakier" stone?

 

[Rockdiamond]

really great questions!!
When people here talk about "light performance" they are generally repeating promotional claims of sellers. There's no mention of how one will be looking at the diamond.
Light moving through a diamond can take many different forms, and what appeals to each of us is different.
Therefore what one person sees as "great light performance" another person may not like at all.
Same with a "good aset"- it's like saying "a good pizza"- my idea in NYC may be totally different than someone in Chicago.
Your points about different lighting, and the angle at which the light is hitting the diamond are spot on as well.
ASET can ONLY telling us how the light will behave if the diamond's table ( flat part on top) is parallel to the ceiling. Most of the time it won't be.

"Leakage" is a term designed to bolster the promotional "light performance" claims.
Leakage an essential element in many diamond shapes.

In a nutshell, both terms -"leakage" and "Light performance" -are an attempt to make a tasted based perception sound like science.

 

[nyquestioner]

David, thank you for your response.
I understand that there are two philosophies on the general matter of light performance metrics and ASETs.
Therefore, I would also like to hear from trade members who _are_ big proponents of light performance metrics. Especially those who have created cuts to have "ideal" light performance.
If you are a proponent of light performance metrics, what would you tell a customer who generally is in environments with lamplight (non perpendicular light source) vs overhead light? What would you tell them about earrings vs. rings? Should a customer be _looking_ for leakage in certain circumstances, even with MRBs?

 

[Rockdiamond]

You're welcome fellow NY'er!!
I will be interested to hear an answer from someone who promotes "Ideal Light Performance" that actually addresses your perceptive question.
How can a leaky stone be beautiful and have great light performance?
Many are and do.

in general, the job of promoting "Light Performance" here on PS has been passed on to consumers who buy into this way of looking at diamonds.

Watch out for leakage!!!

 

[Karl_K]

a: off angle lighting being under considered is a problem with ASET based technologies. I have been saying that for years now.
b: leakage has next to nothing to do with the ability to return off angle lighting to the eye.

It is possible to have a good looking ASET and good off angle light handling.
It is a something I take into account when working with a design.

 

[nyquestioner]

Karl, would it be correct to say that you cannot predict by ASET how a stone will perform in off-angle lighting? i.e., some stones with good asets will do well in off-angle lighting and other stones with similar asets will not? or is there some information that you can glean from the aset about this?
Is it possible to do off-angle asets?
Regarding the specific case of earrings, if a customer wants earrings that will have good brilliance in overhead lighting, would there be any reason to choose stones with ideal light performance? if you had a choice between AGS1 and AGS0 stones, would there be a reason to think the AGS0 stones would be more brilliant with off-angle lighting?

 

[Karl_K]

Karl, would it be correct to say that you cannot predict by ASET how a stone will perform in off-angle lighting? i.e., some stones with good asets will do well in off-angle lighting and other stones with similar asets will not? or is there some information that you can glean from the aset about this?
Is it possible to do off-angle asets?

It is complex, you could go with more green in aset which is off angled lighting but can sometimes impact brightness in overhead conditions.
But no ASET does not show if a diamond will have the ability to return both well with what is considered a good aset. It does not show secondary light paths. Lets say a virtual facet draws light strongly from the red zone with a secondary draw from the green zone it will appear red.
Step cuts because of the varied angles of the pavilion steps are able to do this much better than rounds.

 

[Karl_K]

Regarding the specific case of earrings, if a customer wants earrings that will have good brilliance in overhead lighting, would there be any reason to choose stones with ideal light performance? if you had a choice between AGS1 and AGS0 stones, would there be a reason to think the AGS0 stones would be more brilliant with off-angle lighting?

A well cut diamond has the potential to return more light than one less well cut.
Some experts me being one of them lean towards well cut FICs over tolk for earrings some of which will get ags0.