A method comprising: receiving one or more reference source images and one or more corresponding non-reference source images having at least one of camera settings and scene settings closest to those of the one or more reference source images, the one or more reference source images comprising image data for one or more reference cards, comprising representations of a set of reference values; generating one or more output images for the one or more corresponding non-reference source images by performing at least one image processing operation for the one or more corresponding non-reference source images; deriving, based on the image data for the one or more reference cards, scene-referred metadata comprising a set of reference values and a corresponding set of coded values, the corresponding set of coded values comprising coded values in the one or more output images, wherein the scene-referred metadata further comprises at least one of information about one or more camera settings with which the one or more reference source images and the one or more non-reference source images are captured, and information about one or more scene settings with which the one or more reference source images and the one or more non-reference source images are captured; and outputting the one or more output images with the scene-referred metadata as a part of image metadata separate from the image data for the one or more output images; wherein the at least one image processing operation is configured to: obtain a modified reference source image or modified scene-referred metadata for the one or more non-reference source images by interpolating or extrapolating the closest reference source images or the scene-referred metadata generated therefrom, and perform the image processing operation based on the modified reference source image or the modified scene-referred metadata. receiving one or more reference source images and one or more corresponding non-reference source images having at least one of camera settings and scene settings closest to those of the one or more reference source images, the one or more reference source images comprising image data for one or more reference cards, comprising representations of a set of reference values; generating one or more output images for the one or more corresponding non-reference source images by performing at least one image processing operation for the one or more corresponding non-reference source images; deriving, based on the image data for the one or more reference cards, scene-referred metadata comprising a set of reference values and a corresponding set of coded values, the corresponding set of coded values comprising coded values in the one or more output images, wherein the scene-referred metadata further comprises at least one of information about one or more camera settings with which the one or more reference source images and the one or more non-reference source images are captured, and information about one or more scene settings with which the one or more reference source images and the one or more non-reference source images are captured; and outputting the one or more output images with the scene-referred metadata as a part of image metadata separate from the image data for the one or more output images; wherein the at least one image processing operation is configured to: obtain a modified reference source image or modified scene-referred metadata for the one or more non-reference source images by interpolating or extrapolating the closest reference source images or the scene-referred metadata generated therefrom, and perform the image processing operation based on the modified reference source image or the modified scene-referred metadata.