Measurement unit of illumination. Lumens are often stated in regard to video display specifications. Higher values mean that the display is able to output more illumination or more light. With higher light output, a video display is easier to see in a brightly lit room. This is especially important with front projection systems, which typically must be used in dim lighting on account of the fairly low light output of the projectors. lumen is technically a unit of luminous flux equal to the light emitted in a solid angle over a spherical surface by a uniform single point of light equal to one candle.