Color rendering in high dynamic range images

If a photograph is reproduced “faithfully”, i.e. preserving the relative colorimetric values of the original scene, the resulting image will often look less colorful and less contrasted than the original scene due to some mechanisms of the human visual system. Film and digital cameras must compensate these effects in order to obtain visually pleasing images, which reproduce the appearance of the original scene. This problem occurs also in high dynamic range (HDR) photography, and tone mapped images may appear slightly hazy if the aforementioned visual effects are not compensated. In this paper we shall briefly recall the technique used by most cameras (both film-based and digital) and show one possible theoretical motivation based on a model of brightness perception. We shall then propose a simple technique which compensates the loss of colorfulness and contrast in tone mapped images, and show in particular how this technique can be combined with a tone mapping operator we recently proposed. Finally, we shall compare the results with those produced by a related method.