In the ordinary Computer Graphics (CG), a three dimensional object is represented on a two dimensional screen. Although there are several ways of projection, perspective projection is the most common way. Perspective projection and many other ways of projections, however, have the disadvantage that an object close to the edge is distorted. Since an object close to the edge is out of sight or out of conscious in many cases, this distortion has not been focused so far. We investigate this distortion quantitatively and propose a way to eliminate it.