Previous chapters considered methods of estimating geometric shape information by using active-lighting methods, which provide photometric characteristics of the target scene and light sources. Because BRDF depends on materials, adequate lighting and analysis provides rich information about those materials. Moreover, multispectral light gives us more robust identification capability. Furthermore, polarization and fluorescence are useful for material classification. Analyzing captured images enables us to separate an image into several photometric components. Additionally, a scene illuminated by multiple lights can be decomposed into an image illuminated by a single light. As such, active lighting is useful, not only for geometrical analysis, but also for photometrical analysis.