The optical diffuser has a transparent base body with a base body surface, which is divided into facets. Each facet has an elevation or a depression correlated or associated with a second curved surface. Respective facets have correspondingly different geometrical shapes. In some embodiments the respective apexes (S) of the elevations or depressions are arranged along a spiral, especially an Archimedean spiral. In other embodiments the apexes (S) are defined by coordinates (x.sub.s', y.sub.s') derived by rotation of coordinates (x.sub.p, y.sub.p) of all points (P), which are defined by an arrangement of facets with regular hexagonal edge contours, about a center (0, 0) through a twist angle (.delta.). Alternatively the apexes (S) are defined by coordinates (x.sub.s'', y.sub.s'') derived from coordinates (x.sub.p, y.sub.p) of all points (P), which are defined by the arrangement of facets with regular hexagonal edge contours, by random variations with the help of a Monte Carlo method. The optical diffuser according to the invention produces a circular soft-edged light field, which is outstanding for photographic applications.