A method of displaying together IR image data and visible light image data corresponding to the same field of view in the same image is disclosed, comprising displaying IR image data in at least a first portion of the image and visible light image data in at least a second portion of the image. The method is characterized by the step of displaying the IR image data according to a colouring scheme adapted to the temperature range relevant to the first portion of the image. The resolution in the relevant temperature range may be increased by applying the entire range of colours available in the colouring scheme to the selected temperature range.