Cylindrical illuminances at office workplaces
Good facial illumination
Harmonious distribution of brightness on faces
The good illumination of faces is important for communication purposes in offices. To achieve this, lighting must provide a bridge between high vertical illuminances in the room and good glare control for the user. Combining horizontally directed light components with wallwashing or ceiling washlighting is ideal. Downlights should be mounted in ceiling areas to the side of the desk. Wide light distribution such as oval wide flood along the longitudinal axis of the desk achieves the required cylindrical illuminances on the face. The actual modelling is the ratio between cylindrical and horizontal illuminance and should be in the range of 0.3 to 0.6.
The challenge for lighting design
With both standing and seated persons, narrow distribution luminaires arranged on one side or directly above create hard shadowing on faces. Dark eye sockets and shadows in the nose and chin areas make the illumination of facial expressions difficult. In addition to this problematic facial detection, another problem at desks is that users themselves cast shadows in their work areas. Webcams used for example in video conferences cannot resolve high illumination contrasts in faces so that areas in shadow appear dark.
