Faces as light probes for relighting

A light probe is commonly used for measuring the illumination of a real scene. Instead of equipping a man-made light probe such as a mirror ball, we propose to use a face in images as a natural light probe. To that end, we construct a statistical reflectance model for faces and use this model to extract the lighting and the reflectance field of an input face. With an iterative procedure, we can obtain the lighting condition from an unknown face image. As a byproduct of this procedure, we also estimate the reflectance field of the same face. By identifying the lighting condition of scene, we can provide an effective solution for various practical applications. First, we can insert a virtual object seamlessly into a real scene by illuminating the virtual object under the lighting present in the real scene. Second, we can relight a face under an arbitrary lighting condition using the estimated reflectance fields. Third, we can swap two unknown faces using the estimates of both lighting and reflectance fields. Based on various experiments, we show that the proposed algorithm is an effective tool for many practical applications: inserting a virtual object into a real scene, face relighting, and face swapping.