A hidden image method comprising: obtaining a first image and a second image, the first and second images providing between them a hidden image and a decoder such that a hidden image is decoded by the decoder when the first image and the second image are superposed at at least one decoding position; printing the first image onto a light transmissive substrate to produce a printed substrate; displaying the second image on an electronic display; and superposing the printed substrate relative to the display at a decoding position to decode the hidden image.