Task lighting
Office task lighting
Localised average lighting
Localised average lighting consists of a luminaire that supplies ambient light as well as task light. Often it is an uplighter with a light source that is directed downward. It is intended to be mounted immediately over the workplace, and it can be either hung from the ceiling, mounted on the desk or a dividing wall, or it can be a free-standing floor lamp.
Freely adjustable task light
The main feature of the freely adjustable task light is evident; you may adjust it freely at any whim or to suit your needs. The lamp presents few limits to how you may position or orient the light. A freely adjustable lamp may include means for glare control, as a honeycomb or parabolic louvre that restricts the light output angle.
Asymmetric task light
The asymmetric task light is intended to be placed at the side of the actual task. The luminaire directs the light obliquely over the desk, with the highest illuminance typically about 1′ to 1′ to the side of the lamp head. It mostly has an arm system that holds the lamp head horizontally irrespectively of the arm movement – a parallel arm. Asymmetric lamps often cause more reflected glare than other lamps. In workplaces where people use different table heights, an asymmetric lamp may cause direct glare due to its absence of means for glare control (ref:1).
Contrast reduction
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.
Contrast reduction by veiling glare: In the left picture, the lamp is positioned where it does not cause glare, in the right picture it is placed where it produces maximum reflected glare.
Ideally, text should be rendered with highest possible contrast.
When the light source is reflected in the print, the contrast is reduced.
References
The glare free lamp, by Urban Domeij
Categories: Lighting
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