Update: Projection Screens
Is there a potential downside to screens that reflect light equally in all directions? The answer is yes. Here's the justification often used for selecting higher-gain screens. These screens will give the primary viewer (in the money seat) more isolation from light coming into the screen from the sides than can be obtained from a low-gain screen. Light coming into the screen from the sides will be more visible to the viewer on a low-gain screen.
So what light could possibly be coming in from the sides of the screen? In an ideal viewing environment, there would be no light coming into the screen from anywhere but the projector. It's when you start making compromises in the environment that you get into trouble with light coming in from the sides. Obviously, if you have any room lighting hitting the screen it will compromise image quality.
The next source of light falling back into the screen comes from reflections of screen light off sidewalls, the ceiling or floors. For those who have mirrors on the back wall of their home theater, take a cue from vampire movies and cover them up while watching movies.
A low-gain screen, something at or below the characteristics of our original 1.3 gain screen, is required for a uniform image for a viewer of HD content. The reflectivity of the environment around that screen needs to be minimized in order for that screen to work. As the reflectivity of the screen becomes more uniform than 1.3 gain, the environment around the screen becomes more critical.
While on the topic of room light isolation, gray screens have an advantage over white screens for reducing the visibility of unwanted light hitting the screen. Just as the gray material is used to pull down the ambient light level of the projector, it will also darken any unwanted light hitting the screen. Knowing that we use gray screens to pull down the ambient light of a projector, and that such screens give us some ambient light rejection qualities, we suggest the use of gray screens from the Da-Lite Affinity series where they match the installation.