AGS light performance

[heyyoumob]

Hi all,
When a diamond is graded on light performance, does this take into account the shape?

Ie. cushions are generally not as brilliant as rounds, so is a ags 0 light performance in a cushion not necessarily more brilliant than a ags 1 round brilliant?

Or is the light performance eating irrelevant to shape, and an AGS 0 always more brilliant than an AGS 1 (wellin theory anyway) ?

 

[diamondseeker2006]

Rest assured that any AGS 0 stone is going to be a top performer compared to a vast majority of other diamonds. You have to choose based on what shape/type of stone you like best, and then find the best cut one that you can (that is pleasing to your eye, of course). Certainly choosing an AGS 0 diamond is a good way to do that! If I like a newly cut antique cushion best, for example, then certainly I am not going to be concerned with comparing it to a round brilliant. Both may be great performers, but they are very different in shape/design! If the diamond is for you, then you need to decide what shape you like. If it is for someone else, you need to find out what they like!

(I am sure someone can come along with a scientific answer, but I would not choose a stone based on that answer.)

 

[Karl_K]

The shape/design is taken into account different designs have different criteria to get the grade.
Btw it is not true that a cushion can not be as brilliant as a RB measured by the intensity of the light beams.
I can even have more in volume also.
AGS0 and ASET does not measure brilliance it at best roughly predicts potential to draw light from arguably the brightest areas around a person in specific lighting conditions and viewing positions.
Roughly is because the contrast model is badly flawed.
In a typical home with side lamps and tvs as a light source green zone in ASET is the brightest area of light not red. Typically people will move the diamond while viewing it to put the light in the red zone if the diamond needs it.
In a typical kitchen where bright ceiling light is the norm the light is generally in the red aset zone.

 

[heyyoumob]

Many thanks.
I was majorly generalising with my statement of cushions being less brilliant.
Which I understand is a faux pas with diamonds, as they all need to be taken for their own merit and a certificate can only say so much.

 

[MelisendeDiamonds]

Hi all,
When a diamond is graded on light performance, does this take into account the shape?

Ie. cushions are generally not as brilliant as rounds, so is a ags 0 light performance in a cushion not necessarily more brilliant than a ags 1 round brilliant?

Or is the light performance eating irrelevant to shape, and an AGS 0 always more brilliant than an AGS 1 (wellin theory anyway) ?

You can't compare brilliance between two different facet structures using the AGSL cut grading system.
AGSL grade measures brilliance of a sample versus a theoretical optimal standard. The standards are different for each facet structure as well as for different outlet shapes.

Small differences in brilliance may not impact overall appearance as much as other factors such as flash size, scintillation, fire, outline shape etc.

 

[Texas Leaguer]

As the others have said, the AGS light performance system grades different facet arrangements/shapes against like kind. The standard for each one has to be developed separately. Currently there are a handful of shapes that the AGSL issues cut grades on. Round and princess are the most commonly seen along with certain types of cushions and proprietary cuts.

There is an article here on pricescope in the Articles/Diamond Grading section on how AGSL goes about grading princess cuts. Some of the considerations and methodologies discussed also apply to other shapes.