The Relevance of Viewing Behavior and Movement in an Open-Plan Office for Predicting Light Levels at the Eye

Office lighting design should not only take into account comfortable vision, but also the non-image-forming effect of light. The latter is commonly measured or simulated as the amount of light falling vertically on the eye when facing a computer screen. In reality, light at the eye might differ from this assumption due to a person’s changing face orientation and movement within a space. This article compares light measured vertically toward a computer screen (static condition) with light at the eye position of office occupants while seated at a desk (dynamic-fixed condition) or moving freely within an open-plan office (dynamic-free condition). Light was quantified using melanopic equivalent daylight illuminance (mEDI). Face orientation was measured using a video-based method. The results show that the average difference between the mEDI for the static and dynamic-fixed conditions was small (7 l× or −1%), whereas for the static and dynamic-free conditions, it was considerable (282 l× or −21%). These findings indicate that changes in the position of office workers might need to be considered in office lighting design.