There is described a printed security feature (10) provided onto a printable substrate, which printed security feature includes a printed area (11) with at least a first printed section consisting of a multiplicity of geometric elements (GE, 15) printed with a given distribution over the printed area. The geometric elements are printed with at least first and second inks which exhibit the same or substantially the same optical appearance when illuminated with visible white light, such that the printed security feature produces a first graphical representation (A1) when illuminated with visible white light. At least the first ink is an ink which responds to non-visible light excitation by producing a characteristic optical response differentiating the first ink from the second ink. The printed security feature produces a second graphical representation (B1) when illuminated with non-visible light, which exhibits a distinctive two- dimensional graphic element (B) which is revealed only when the printed security feature is illuminated with non-visible light. The first printed section is subdivided into at least first and second printed portions (P1, P2), adjacent to the distinctive two-dimensional graphic element, and a third printed portion (P3), inside boundaries (200) of the distinctive two-dimensional graphic element. In the first, respectively second printed portion, the geometric elements are printed with the first, respectively second ink. In the third printed portion, the geometric elements are subdivided into first and second contiguous portions (GE_a, GE_b) which are respectively printed with the first and second inks. The first and second inks are printed in register one with respect to the other so that the boundaries of the distinctive two-dimensional graphic element are not visible when the printed security feature is illuminated with visible white light and the distinctive two-dimensional graphic element only becomes visible when the printed security feature is illuminated with non-visible light.