Diamond Light Performance
by Lars Larsen
May 17, 2010 / Diamond Education
The light performance or “life” of a finished, polished diamond is described as the overall, face-up appearance, produced by a combination of the three optical effects of Brilliance, Fire and Scintillation. Light performance analysis is used today by leading laboratories as an integral component in the grading of cut quality.
Brilliance is the term used to describe the combined internal and external reflections of unaltered, white light returned from the crown of a diamond.
Fire is the name used for light which has been dispersed into its individual spectral colours by a prism-effect which occurs when light, after being internally reflected, returns through the angled facets of the bezel.
Scintillation or “sparkle” is the name given to the alternating on-off flashes of Brilliance and Fire created when either the diamond, the light source or the observer is in motion.
The light returning from within a diamond forms a distinct pattern created by the contrasting light and dark areas of reflected light and light extinction.
A light pattern, in effect, presents a virtual map of the reflective surfaces of the facets and can be used simultaneously to gauge proportions – by comparing the position and degree of light return to that of light leakage – and to determine the degree of internal or optical symmetry of a diamond.
Light patterns are also referred to as symmetry images and are observed and analysed with the aid of special magnifying, reflective imaging or symmetry viewers.
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