A Single-Shot Light Probe
Paul Debevec    Paul Graham    Jay Busch    Mark Bolas   
USC Institute for Creative Technologies

We demonstrate a novel light probe which can estimate the full dynamic range of a scene with multiple bright light sources. It places diffuse strips between mirrored spherical quadrants, effectively co-locating diffuse and mirrored probes to record the full dynamic range of illumination in a single exposure. From this image, we estimate the intensity of multiple saturated light sources by solving a linear system.

Recording on-set illumination to render virtual objects into a real scene is often accomplished by acquiring a panoramic, high-dynamic range (HDR) image where the object is to be inserted, and to use this HDRI map as an image-based lighting source on the CG object. The spherical panorama can be obtained by stitching HDR fisheye images from different directions, or more rapidly by photographing a mirrored sphere. Shooting HDR is necessary to capture light sources - they typically exceed ambient light by several orders of magnitude - but it requires recording, aligning, and assembling a range of exposures which can be time-consuming and complicates dynamic capture. If there is just one bright light in the scene, its intensity can be determined from an image of a diffuse gray ball, with the remaining illumination imaged accurately in the mirrored sphere. Even so, two images are required, and only one saturated light source is estimated. We relieve both restrictions.