The most uniform screen we make is our front projection Matte White. That is, the observed brightness of such a screen doesn't change with viewing angle. Thus the eye perceives as much brightness at the center of the screen as it sees at the corners which in turn is the same amount of brightness visible from any angle of view. Gain, we must always remember, does not imply amplification. No screen can add power to the display.
All available brightness is created by the projector and only the projector.
So when a gain screen exhibits increased brightness at its center, it is certain that it has robbed that extra energy from somewhere else. With all diffusion screens therefore the higher the gain, the lower the uniformity. This is the principal reason to recommend low gain screens whenever possible. Our Video Vision, for example, is an extremely efficient diffuser whose uniformity can be degraded only by projector limitations. When the diffusion coating contains more than a diffuser, however, uniformity problems particular to rear screens begin to arise.