Halftone prints are characterized by dots 0/ different sizes arranged in a screen of constant frequency, i.e. thepictures are amplitude-modulated. Pictures characterized on the other hand by dots of constant area arranged at random and with a mean local frequency according to the local optical density, are frequency-modulated pictures. Pictures of this nature have now been cakulated and printed. Compared with halftone prints the following advantages were ascertained: brighter colours, higher resolution of details and higher contrasts. Moreover the tone reproduction proved to be more constant over the production run.

Une autotypie est caracterisee par des points a trame de grandeur differente, arranges dans une trame de [requence constante. C.-a-d. l'image est moduLee des amplitudes. Une image caracterisee par des points a trame de grandeur constante, arranges aLeatoirement a des distances variables selon la densite locale, est au contraire modulee des frequences. Des images pareilles etaient calcuLees et imprimees en offset. La comparaison avec l'autotypie montre les advantages suivants: des couleurs plus lumineuses, un pouvoir resolvant eleve et des contrastes eleves. En outre la reproduction des valeurs tonales etait plus stable.