1. A method of generating an image signal of a representation of a captured physical scene, the method comprising: providing, in the image signal, a first pixelised picture encoding and a second pixelised picture encoding, each pixelised picture encoding having a luminance component and a color component represented by sets of code words of a number N of bits, corresponding to a two-dimensional array of pixel positions; encoding a first image of the captured physical scene with luminance and color code words in the first pixelised picture encoding; encoding dynamic range extension data in the color component of the second pixelised picture encoding in lieu of color values, the dynamic range extension data corresponding to at least one region of pixels in the first image and representing a dynamic range extension transformation in the luminance component to obtain an increased dynamic range image based on the first pixelised picture, wherein the dynamic range extension data includes the luminance transformation or a modification of the luminance transformation.