Leakage does also cause darkness; the crown facet area of the deep stone in Fig 2 is darkened because of leakage. But leakage can also produce good contrast. The small ‘v’ shaped dark areas at 12 o’clock near the girdle in the Tolkowsky stone in Fig 2 show contrast that arguably improves this diamonds appearance.

Princess cuts exhibit very little head obscuration. Much of the contrast in a princess cut is caused by leakage, and if it occurs in small and well distributed ‘virtual facets’, leakage can cause good contrast. But the four triangular dead areas that you sometimes see in Princess cut’s are an example of poor contrast caused by too much leakage.