Lighting system brings outdoors indoors STUTTGART, Germany, Jan. 3 (UPI) -- Researchers in Germany say they've developed a lighting system that can make workers feel as though they're working outside under the open sky. Scientists at the Stuttgart-based Fraunhofer Institute for Industrial Engineering say the system creates a feeling of spaciousness and freedom through a luminous ceiling that extends across an entire room and simulates lighting conditions that resemble those produced by passing clouds. The ceiling is composed of panels, each 20 inches by 20 inches, containing light emitting diodes with a diffuser film to create homogeneous lighting that illuminates the room throughout, a Fraunhofer release said Tuesday. The intensity of the LEDs can be varied to simulate natural lighting conditions on a cloudy day, researchers said. "The LEDs allow us to simulate these dynamic changes in lighting in a way that is not directly obvious to the naked eye," researchers Mathias Bues said. Otherwise the lighting might distract people from their work. But it does need to fluctuate enough to promote concentration and heighten alertness. In a study with 10 volunteers who carried out their daily work over the course of four days under different lighting conditions, 80 percent preferred the dynamic, changing "outdoor" lighting over fixed illumination, researchers said.