Perceived spatial brightness when lighting up vertical or horizontal surfaces

​Until now, the focus in lighting design has mainly been on illuminating the areas and surfaces where visual functions must take place. Lighting design has therefore most of all been a practice in optimizing energy performance and compliance with rules. With the development of newer technologies in lighting control, it has become widespread that lighting not only aims to meet visual needs, but also stimulates other non-visual human factors.
The purpose of this report is to evaluate and to generate knowledge about perceived spatial brightness by illuminat-ing vertical or horizontal surfaces. The intention is to get closer to a clarification of whether and how much the light on the horizontal plane can be reduced by compensating with light on vertical surfaces so that perceived spatial brightness is still the same.
In this respect, the report is particularly interesting for lighting designers and other professionals working with lighting systems.