Task lighting:

Often task lighting refers to office lighting, where the task light is used to increase illuminance on the reading area. However, the illuminance level is not the only factor governing visibility. Contrast is also important, and a poorly positioned light source may cause contrast reduction, resulting in loss of visibility. Therefore, it can be argued that the most important purpose... of task lighting in the office is not increasing illuminance, but improving contrast.

Different strategies for office task lighting exist. The three main approaches are:
•Localised average lighting, where a lamp supplies both ambient light and task light
•Freely adjustable task light
•Asymmetric task light, where the lamp is placed at the side of the work area