1. A method for providing a rendered composite image having image content encoded therein, and for enabling depth discrimination of the image content, comprising: encoding a first source image in a composite image to be perceived upon illumination by a first narrowband illuminant having long wavelengths of light within the visible spectrum; encoding a second source image in the composite image to be perceived upon illumination by a second narrowband illuminant having short wavelengths of light within the visible spectrum; and rendering the composite image to provide a rendered composite image on a substrate having the first source image recorded in the form of an imagewise pattern of a first narrowband colorant, and having the second source image recorded in the form of an imagewise pattern of a second narrowband colorant, wherein the first narrowband illuminant has a respective spectral power distribution that is substantially the complement of the spectral characteristic of the first narrowband colorant and the second narrowband illuminant has a respective spectral power distribution that is substantially the complement of the spectral characteristic of the second narrowband colorant; whereby the rendered composite image is susceptible to depth discrimination upon selectively subjecting the rendered composite image to simultaneous illumination incorporating the first and second narrowband illuminants, such that at least one of the first and second source images is depth discriminated with respect to the image content of the rendered composite image.