Measuring light as perceived by the human eye is an important element of "smart building" design, as well as other more conventional lighting projects. To correctly control lighting systems based on available ambient light, a photometric sensor that detects light in the correct wavelengths must be used. The typical human eye is sensitive to light with wavelengths between 390 nm and 750 nm. Perception of different components of this spectrum can differ significantly between individuals, however. On the average, human sensitivity to light can be represented by a bell curve between approximately 450 and 650 nm and this is often used as a representative of the entire visible spectrum.
Smart buildings use photometric sensors to determine when to raise and lower window coverings or turn lights on and off to optimize lighting efficiency. Using smart building design can help save energy, water, time, and money.