The basic proposition of digital imaging is summarized in Figure 2.1. Image data is captured, processed, and/or recorded, then presented to a viewer. As outlined in the caption, and detailed later, appearance depends upon display and viewing conditions. Viewing ordinarily takes place in conditions different from those in effect at the time of capture of a scene. If those conditions differ, a nontrivial mapping of the captured image data – picture rendering – must be imposed in order to achieve faithful portrayal, to the ultimate viewer, of the appearance of the scene (as opposed to its physical stimulus).