Lighting design for the biological effect of light
The rooms in which we live, work, learn or relax are extremely varied. Professional lighting design thus considers room size, ceiling height, the ingress of daylight and of course the activity primarily carried out by people in the specific rooms.
Suitable luminaires must be selected and arranged in accordance with these criteria, and lighting design under biological aspects also places special demands on both luminaires and their distribution of light in the room. Lighting designers have to take into account several factors to make sure that light has genuinely biological effects.
Biologically effective lighting must also comply with visual quality needs, and whether at desks, on machines or in operating theaters, light has to optimally illuminate the work area without adverse affects. A good lighting installation coordinates levels of illuminance according to visual tasks and distributes luminance uniformly in the room. It also restricts direct and reflected glare and also has good color rendering. The light does not flicker and takes into account the level of daylight entering. Fundamental requirements are stipulated by the DIN EN 12464-1 standard, "Light and Lighting – Lighting of Indoor Workplaces".
Light color is decisive
The various color temperatures of fluorescent lamps are dependent upon their mix of fluorescent material, and this gives various light spectra characteristics that have different effects on the circadian system of people. Light with a higher blue component for example is more effective with regard to our circadian rhythm than warm white light colors. Light color is specified as color temperature using the unit Kelvin, and characterizes the color appearance of the light of a lamp. The light color of the sky varies mainly between 6,000 and 10,000 Kelvin.
For light to be biologically effective, eyes must be able to perceive bright areas in a room, and wide-area luminaires illuminate the room for this purpose. Alternatively, luminaires with indirect light components illuminate the ceiling and upper third of the walls. The activating effect of light is usually desired during the day, and warm light colors are selected during the evening time. This means that the visible brightness in the upper area of the room can be reduced. With dynamic lighting, it must be considered that the spectrum emitted from a lamp is not negatively influenced by the luminaire or ambient colors in the room.
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