Cut performance is an aggregate diamond characteristic, based on both fire and brilliance. It shows how vibrant the diamond is.

Fire is colored flashes that we observe in colorless diamond. Perceived Fire strength depends on colored flashes quantity, size, duration, brightness, saturation and distribution.

Fire is the simultaneous (local) contrast of colour that is observed in a diamond. The contrast of this colored image depends on surrounding areas and on the duration of a colored flash.

If the colored flash is too fast the eye is not able to comprehend its colour and such a flash is perceived as scintillation. If the colored flash lasts too long its total contrast is less than the sum of the contrast of two separate shorter colored flashes of half the lifetime of the initial flash.

For a flash to be perceived as colored it should not be neither too fast, too small or too bright; when combined these factors make a colored flash appears to a human as scintillation and not a fire flash.

Diamond brilliance is an illusion caused by the fact that the perceived brightness of the object significantly exceeds its actual brightness. This may occur when several parts of the object with different brightness are observed within a single space-time domain. In the case of a diamond, these parts are its virtual facets. Two virtual facets belong to the same space-time domain when an observer can not separate them due to spatial or temporal limitations of the sense of vision.

Optical symmetry shows how symmetric diamond looks when viewed face-up. Score is calculated from crown (ASET) image for fancy shapes and crown (ASET) and pavilion (Hearts) images for round shapes.

Diamond with the same weight can have different visible size depending on their shape. This visual size is described by spread characteristic. Positive spread means that diamond looks larger than Tolkowsky round with same weight, negative means opposite.

Face-up fluorescence score show percentages of diamond area that belongs to different fluorescence grade for diamond image taken face-up in UV 385nm light.

Diamond with the same weight can have different visible size depending on their shape. This visual size is described by spread characteristic. Positive spread means that diamond looks larger than Tolkowsky round with same weight, negative means opposite.