HERNÁNDEZ-RODRÍGUEZ, CASTELÁN: IMPROVING PHOTOMETRIC CONSISTENCY 1 A method for improving consistency in photometric databases

Building photometric databases usually requires the gathering of images of a still object under different light source directions. During this process, unexpected artifacts such as noise, shadows, inter-reflections and other unwanted effects introduced by the sensibility of the camera may appear along the database, diminishing its consistency as a whole and therefore its suitability for the purposes of photometric analysis. This paper describes a method for improving photometric consistency in image databases acquired under photometric rigs. The main idea of our approach is to build and analyze a luminance matrix storing the reflectance behavior of each pixel under the different light source directions. To this end, we propose to fit sinusoidal functions to the singular vectors of this luminance matrix in order to improve its agreement with Lambertian reflectance. Experiments demonstrate that our method improves the photometric consistency of the database, providing stability for the purposes of photometric analysis of the database and surface shape recovery.