Large area luminaires with high light outputs and a high level of uniformity. Dimensions and light outputs of these luminaires are innovative and exceptional. They are also suitable for outdoor use, i.e. as a dust-proof and jet-proof version. The newly developed, light diffusing matt surface of the diffuser provides maximum uniformity and transmission by the luminous surface. The high light outputs significantly reduce the number of luminaires required to illuminate large and high rooms. The long life of lamps and low number of luminaires installed reduce installation, maintenance and operating costs.