Projection screens are installations consisting of blank surface and a support structure used for displaying a projected image for the view of audience. Projection screens may be permanently installed as in a movie theaters, painted on the walls or semi-permanent or mobile as in a conference rooms or other non-dedicated viewing space. Uniformly white or grey screens are used almost exclusively as to avoid any discoloration to the image, while the most desired brightness of the screen depends on a number of variables, such as the ambient light level and the luminous power of the image source.