1. A method of making a hologram or diffraction grating, comprising the steps of: forming in a surface of a substantially transparent substrate a continuous relief pattern over an area thereof that is capable of forming a recognizable image upon polychromatic viewing light being reflected from the surface relief pattern, and forming non-continuous, substantially opaque reflective layer areas over said surface relief area with a pattern that allows simultaneous viewing completely through the substrate across said area and viewing of an image reconstructed from the portions thereof to which said reflective material is attached, said step forming the pattern of said discontinuous opaque reflective layer portions with a spacing in excess of 25 such portions per inch in at least one direction across said relief pattern.