Given a general affine camera, we study the problem of finding the closest metric affine
camera, where the latter is one of the orthographic, weak-perspective and paraperspective
projection models. This problem typically arises in stratified Structure-from-Motion methods
such as factorization-based methods. For each type of metric affine camera, we give a
closed-form solution and its implementation through an algebraic procedure. Using our
algebraic procedure, we can then provide a complete analysis of the problem's generic …