Seamless stitching of image projected from multiple projectors onto a spherical screen allows very high-resolution image display and brings observers a highly realistic feeling. An optimum arrangement of such projectors is desired from the cost-performance point of view. As a preliminary experiment for such consideration, the relationship between the viewing angle and the ratio that an observer's gazing point is within the viewing angle was investigated and the subjective evaluation with images in which the resolution was reduced in the peripheral region was performed.