Study about Increasing Brightness using Task-ambient Lighting in Offices

We conducted subjective experiments to determine an ideal method for achieving both energy saving and comfort in office lighting. The experiments were conducted in an actual office under 48 conditions of lighting and furniture, such as different average illuminance, lighted areas, reflectance, and height of partitions, and added wall-washers. Luminance images were captured from the subject's viewpoint, and converted into brightness images based on the Nakamura method. We then analyzed the relationship between the perceived brightness and the brightness images. In the results, the subjective evaluation value of the brightness of the room strongly correlated with the average values of the brightness scale of vertical components, such as a wall or partition, calculated from the brightness images. This suggests that we can reduce the electricity consumption of lighting and achieve higher perceived brightness without losing comfort by raising the brightness of the vertical components in the field of view.