Light Behavior Trinity
PGGL uses ImaGem’s technology to analyze the light behavior of a loose or mounted diamond. ImaGem has implemented a three-factor light behavior assessment system based on human perception. This system represents a new way to quantify a diamond’s beauty as seen by the human eye.
ImaGem’s approach for measuring a diamond’s optical performance is determined by brilliance, intensity and sparkle. By precisely measuring these, PGGL can accurately and repeatedly define a diamond’s light handling ability.
The definitions of these terms, while technical, help to explain how each factor influences a stone’s overall beauty.
Brilliance: The measure of Brilliance represents the average light return when a diamond is viewed in the face up position.
Technical Definition of Brilliance: A measure of a stone's overall strength of light return that represents its average light return in the face-up position. This measure is determined by computing the mean gray-scale value of all pixels within the face up view of a diamond. Brilliance is average light return.
| Excellent | > 150 |
| Very Good | 120 < 150 |
| Good | 110 < 120 |
| Fair | 100 < 110 |
| Poor | < 100 |
Sparkle: Sparkle is a measure of those flashes of reflected external light and refracted internal light that gives diamonds "life" or “pizzazz”. The greater the number of these flashes, the higher a stone's sparkle.
Technical Definition: Sparkle is measured by the standard deviation of the gray-scale value of the light return in the face-up view. Sparkle is a static predictor of potential scintillation.
| Excellent | > 70 |
| Very Good | 40 < 70 |
| Good | 20 < 40 |
| Fair | 10 < 20 |
| Poor | < 10 |
Intensity: Intensity is a measure of the light and dark areas and how they combine to show an interesting pattern. A symmetric pattern in a diamond indicates high intensity.
Technical Definition: The ratio of the brightest set of pixels compared to all the pixels in the face-up view. Highly symmetric diamonds tend to have increased intensity. Intensity is a measure of contrast.
| Excellent | > 160 |
| Very Good | 125 < 160 |
| Good | 115 < 125 |
| Fair | 110 < 115 |
| Poor | < 110 |
Comparison of Diamonds using Direct Measurement of Light Behavior
Light Behavior
Image
| 
| 
| 
| 
|
Brilliance
| 113
| 118
| 123
| 165
|
Sparkle
| 30
| 38
| 58
| 92
|
Intensity
| 114
| 120
| 162
| 302
|
Overall Light
Behavior Grade
| Fair
| Good
| Very Good
| Excellent +
|