A method of manufacturing an image pattern for a security device includes providing a metallised substrate; applying a first photosensitive resist layer to a substrate first metal layer exposing the resist layer to radiation; exposing the resist layer to a first reactant substance; activating a cross linking agent in the resist layer; exposing first and second pattern elements of the resist layer to radiation of a wavelength to which the resist layer is responsive whereupon newly-exposed first pattern elements of the first photosensitive resist layer react, resulting in increased solubility by the second etchant substance, the second pattern elements remaining relatively insoluble by the second etchant substance; and applying first and second etchant substances to the substrate whereupon the first pattern elements of both the first resist layer and the first metal layer are dissolved, the remaining second pattern elements of the first metal layer forming an image pattern.