Details of the image formation in the low temperature field ion microscope are discussed. The hopping height of the rebounding gas atom, which depends on the atom's polarizability, the tip temperature, tip radius, and field, is significant for the resolution. Photographs of tungsten and rhenium surfaces with the atomic lattice resolved and in different states of disorder are presented. A color printing technique, which permits finding quickly a few displaced atoms among the many thousand that are visible, is described.