We measured the field-emission properties of nanostructured carbon films (NSCFs), carbon nanotubes, and carbon nanoparticles, using a microtip and a large area phosphor-screen anode. The normal distribution of turn-on electric fields which was measured using a microtip anode from 100 square cells of 30 X 30 mu m(2) for each NSCF indicated an asymmetric distribution of field-enhancement factor beta with a large-beta tail. The direct deduction of the field-enhancement factors via fitting of current-versus-voltage curves to the simplified Fowler-Nordheim (FN) equation with a series-resistance effect confirmed the asymmetric beta distribution. Moreover, field-emission features observed using a large area phosphor screen, such as a slight curvature in the FN plots at the low voltage regime and applied-field-dependent exponential increase of emission-site densities, turned out to be consistent with the asymmetric 8 distribution. (c) 2006 American Vacuum Society.