A measurement of light that has been standardized by ANSI. It is commonly used to rate the brightness of a data projector. An ANSI lumen rating uses an average of several measurements taken across the face of the light source. A small room typically requires from 200 to 300 ANSI lumens, whereas a large room may require from 400 to 600. A large auditorium may need 2000 or more. See lumen.