Lighting louvers formed by transverse and longitudinal blades improve the performance of indirect ambient light luminaires by increasing light output, widening the output of the luminaire's maximum intensity light, or both. These lighting louvers include at least one of the following features: non-symmetrically shaped apertures, wider apertures over (or under) the luminaire's lamp(s), longitudinal blades of shorter height nearest the lamps, and longitudinal blades having differently curved longitudinal sides. Each of these features contributes to improved luminaire performance.