Halo, gradient reversal, shock

Halo: Gamut mapping of an original color image may produce unwanted artifacts in the rendered image. one such artifact is referred to as a halo. halo artifacts occur near edges of objects in the rendered image, and are a consequence of using spatially dependent Gamut mapping algorithms to map an original color image onto a constrained color space. in fact, it adds shadow and light information to edge.

Gradient reversal: gradient reversals are gradients that after manipulating the image, change their direction

Shock: the region quickly evolves into a step-wise discontinuity with infinite gradient and zero
Conductance known as a "shock ."