Optical Performance Evaluation

Optical Performance Evaluation describes the beauty of a diamond with numbers, calculated automatically from captured video.

The beauty of a diamond can often be described by these properties:

• Fire
• Brilliance
• Symmetry
• Fluorescence
• Size

Optical Performance Evaluation is a quantitative description of these properties. Our technology captures videos of a diamond and calculates the evaluation automatically. The calculation:

• is based on human perception, including stereo vision;
• allows you to compare diamonds of different shapes;
• takes diamond size into account, as in real life.

Fire

Fire is the colored flashes that we see in a colorless diamond. How strong the fire looks depends on the number, size, duration, brightness, saturation and distribution of the colored flashes.

Fire is the simultaneous (local) contrast of color in a diamond. The contrast of a colored flash depends on the areas around it and on how long the flash lasts.

If a colored flash is too fast, the eye cannot see its color, and the flash looks like scintillation. If a colored flash lasts too long, its total contrast is lower than the sum of the contrast of two shorter flashes, each half as long as the original flash.

A flash looks colored only when it is not too fast, not too small and not too bright. When a flash is too fast, too small or too bright, a person sees it as scintillation, not as a fire flash.

Example: https://cutwise.com/~BTrD

For more on fire and the other optical performance properties, read our Australian Gemologist article "How diamond performance attributes: Brilliance, Scintillation and Fire depend on human vision features":

Download the article (PDF)

Brilliance

Diamond brilliance is an illusion: the diamond looks much brighter than it actually is. This happens when a person sees several parts of an object with different brightness within one space-time domain. In a diamond, these parts are its virtual facets. Two virtual facets belong to the same space-time domain when the observer cannot see them as separate, because of the spatial or temporal limits of human vision.

Example: https://cutwise.com/~Iesy

Cut Performance

Cut performance is a combined characteristic of a diamond, based on both fire and brilliance. It shows how vibrant the diamond is.

Example: https://cutwise.com/~E_gM

Optical Symmetry

Optical symmetry shows how symmetric a diamond looks face-up. For fancy shapes, the score is calculated from the crown (ASET) image. For round diamonds, the score is calculated from the crown (ASET) image and the pavilion (Hearts) image.

Example: https://cutwise.com/~xlRZ

Spread

Diamonds of the same weight can look different in size, depending on their shape. Spread describes this visible size. Positive spread means that the diamond looks larger than a Tolkowsky round of the same weight. Negative spread means that it looks smaller. Read more in Apparent Size.

Example: https://cutwise.com/~YM2C

Fluorescence

The Face-up Fluorescence score shows the percentage of the diamond area that belongs to each fluorescence grade. It uses a face-up image of the diamond taken under 385 nm UV light.

Example: https://cutwise.com/~kki_

Pavilion Fluorescence images are similar to the images that laboratories use to grade fluorescence. They are captured under 385 nm UV light.

Example: https://cutwise.com/~CH1y

Optical Performance Scores in Cutwise

Each score has two forms:

• Absolute score (value) shows the absolute characteristic of the diamond, for example how much fire or brilliance it has.
• Relative score (grade) compares the diamond with a standard Tolkowsky round of the same visible area. It is available for Spread, Fire, Brilliance and Cut Performance.

For example:

• Fire absolute score = 1.4
• Fire score of a Tolkowsky round with the same area = 1.5
• Relative score = 1.4 / 1.5 = 0.93

The grade is calculated from the relative score. The width of the grade marker shows the accuracy of the value.

See also Optical Performance Scores in the API.