The optical diffuser has a transparent base body with a first 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 Archimedian 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 a regular hexagonal edge contour, 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 the regular hexagonal edge contour, 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.