  We perform detailed numerical simulations of field ion microscopy images of
faceted crystals and compare them with experimental observations. In contrast
to the case of crystals with a smooth surface, for a faceted topography we find
extreme deformations of the ion image. Local magnification is highly
inhomogeneous and may vary by an order of magnitude: from 0.64 to 6.7.
Moreover, the anisotropy of the magnification at a point located on the facet
edge may reach a factor of 10.
