Light & Vision
Last Update: February 8, 2012
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Quantifying Light

Being able to accurately quantify and control light as a physical quantity is important to both the art and science of lighting.  For instance, understanding a photometric data sheet can allow a lighting designer to quickly select which luminaires are likely to produce the desired effect for an architectural, retail or outdoor lighting design.

Physical Measures
The basic physical measures used to quantify the amount of light and its distribution are luminous flux, luminous intensity, illuminance, and luminance.  These physical measures are described in the table below, and in more detail in the text that follows.
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Basic Calculations
Lighting engineering requires the use and calculation of each of these quantities to understand how the resulting visual environment is likely to appear, and how well it will support visual performance and health.  These calculations are usually handled by lighting software, but an understanding of the basic calculations can help designers to understand what’s going on inside the black box of lighting software. 
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Light & Vision

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