The work describes the features of processing glow patterns of the field emission projector when obtaining local I–V characteristics of individual emission sites. The features of constructing such dependencies are shown with the example of an experiment with a nanocomposite field emitter. The main factors influencing the analysis of glow patterns are discussed: the illumination effect, the halo effect, adsorption-desorption processes, vacuum discharges, burnout and contamination of the phosphor screen. Algorithms for reducing these effects with the computer processing of experimental data are described.