Often task lighting refers to increasing illuminance to better accomplish a specific activity. 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. The most important purpose of task lighting in the office is not increasing illuminance but improving contrast. General lighting can be reduced because task lighting provides focused light where needed.
Different strategies for task lighting exist. The three main approaches are:
- Localized average lighting, where a lamp supplies both ambient light and task light
- Freely adjustable task light such as a gooseneck, balanced-arm lamp, or swing-arm light.
- Asymmetric task light, where the lamp is placed at the side of the work area
There are also other approaches to task lighting, for example, under-shelf luminaires.
Home task lighting
Task lighting can also be applied to home uses. Many people benefit from dedicated lighting for specific tasks such as cooking, sewing, reading, or paperwork. Home task lighting can be found in fixed or adjustable forms.
Contrast reduction in the office workplace refers to reading objects having decreased contrast compared to an estimated ideal contrast. If a lamp is placed so that printed letters reflect some of the light, their contrast against the paper background will decrease. This happens when a light source is reflected as in a mirror from the print into the eyes of the observer. A poorly placed lamp may render text illegible, regardless of illuminance level. For older persons, increased lighting and contrast is a necessary aid in performing daily tasks such as paying bills or reading.