The modeling technology was verified by comparison of actual photos under a ring shaped light source and Diam Calc 3D models of a yellow round brilliant CZ (Figure 4):

Photo
DiamCalc Image
Figure 4. A colored round brillian cut CZ with proportions close to Tolkowsky is photographed and modeled (botom row) under a ring-shaped, daylight-equivalent lamp.

The DiamCalc software can closely model the appearance of polished colored stones in any lighting condition, thus it is possible to model the appearance of any colored CZ or diamond in various cuts as represented in figure 5.

Magna Colorscope light on	Magna Colorscope light off	Ring 6 cm	Ring 17 cm	Office	Jewelry store (white background)
Figure 5. Five cuts (round, princess, radiant, oval, and triangle) are modeled in DiamCalc software under various illumination conditions. The round, princess, and radiant cuts are scanned models with real symmetry deviations. The oval and the triangle cuts are parametrical models. Each row contains images of the same stone model in different lighting conditions. The ring lightings are symmetrical illuminations, while the office and jewelry store environments are "real situation" illuminations; these stones are modeled face-up.

There are shapes and proportion sets that have better look in one illumination but worse on another. But other shapes are more stable to lighting changes:

Figure 6. A radiant cut apearance is more stable while an oval is better in the Dialite light (bottom row) and a round is better in the Office light (top row). The background is modeled black.