A measure of brightness for projectors under standards set by this body. This specifies an average brightness produced on a screen of known reflectivity using a particular test image, or images. A specification war is underway with each projector claiming a higher and higher ANSI lumens rating. The amount of brightness required for a good job from a projector requires three things to be taken into account, in order of increasing importance: the reflectivity of the projection surface, the size of the projected image, and the amount of ambient light in the room. High output projectors (> 1,000 ANSI lumens) are important for making presentations, class room work and the like. But for home theater use, look for something lower, preferably under 700. It will generally give you a longer lamp life and darker black areas, which are more important for delivering a good quality image. If the projector has an 'economy mode', try using this. If it doesn't throw out the color balance too much, it may well deliver a better home theater image.