Design Considerations
Last Update: October 30, 2010
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Lighting Quantity

Lighting profoundly affects many human reactions to the environment. These human reactions range from the obvious, such as the dramatic beauty of an illuminated landmark or the emotional response of a candlelight dinner, to subtle impacts on worker productivity in offices or sales in retail stores. The profession of lighting design, which grew from a mixture of theatrical and architectural methods, is largely valued for its ability to intuitively and artfully provide high quality lighting consciously meeting visual, environmental and efficiency requirements.

This section reviews the quantitative measurements of lighting design, providing acceptability standards, discussing determination methodologies as well as visual and spectral concerns.

Task Illuminance
Illuminance describes the amount of light falling on a surface. If the surface is horizontal, light striking it is known as horizontal illuminance; if the surface is vertical, it is called vertical illuminance. Some tasks though are at an angle, such as reading a book in a hospital bed.
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Setting Illumination Levels
The IES design procedure is the most widely used and accepted method for determining lighting levels for applications.
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Illumination Based on Spectrum
Illumination recommendations based on lumens and footcandles do not completely account for certain effects of the spectrum of light sources. There are a number of conditions under which details of the light source spectrum need to be considered to better reflect human vision or perception.
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