Considering recent regulation opportunities to develop adaptive lighting for the automotive industry, this paper shows that a characterization of fog based solely on the atmospheric extinction parameter is not sufficient, especially in the perspective of adaptive lighting for road safety. This has been validated on synthetic images generated with a semi Monte-Carlo ray tracing software dedicated to fog simulation as well as with experiments in a fog chamber. Based on observations showing the limits of classical approaches used to characterize fog, a new way to estimate fog extinction at night with a camera is proposed, along with a method for the classification of fog depending on the forward scattering. Results are given and potential applications are discussed. The main contribution is that it allows for the estimation of a parameter linked to the droplet size distribution of the fog.
