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brightness and color perception were improved under white metal halide light under
mesopic conditions.2 By using white light, peripheral vision is improved and energy is
saved compared to a HPS or LPS lighting system.
2-5.2.4 For all exterior lighting applications where peripheral vision is important such
as detecting pedestrians and other potential off axis activity, white light as produced by
a metal halide, fluorescent, or induction lamp is recommended.
2-5.2.5 Lumen effectiveness multipliers may be used to account for the improved
visibility provided by white light as opposed to HPS. Table 2-1 lists lumen effectiveness
multipliers for three different sources. To use the table, determine the appropriate
luminance condition and the source being used. Note that most computer lighting
programs can calculate luminance as an option. From the table, find the corresponding
multiplier. This value is then multiplied by the lumen output of the lamp published by the
manufacturer to determine the effective lumens. Notice that during photopic (10 cd/m2)
conditions, the multiplier for all sources is 1.00 and no adjustment needs to be made to
the lamp lumen output. At lower brightness levels, white metal halide light becomes
more effective and low-pressure sodium becomes less effective. (Because sources are
being compared, one must be set as baseline. In this case, high-pressure sodium is the
base and all values are 1.0 under any brightness condition.)
Table 2-1. Lumen Effectiveness Multipliers vs. High Pressure Sodium3
High Pressure Sodium
Low Pressure Sodium
"Evaluation of Visual Function Under Different Light Sources", (Lighting Research Center, Rensselaer
Polytechnic Institute, Troy, NY, December 11, 1995) p15.
Lewin, Ian. "Lumen Effectiveness Multipliers for Outdoor Lighting Design." Journal of the Illuminating
Engineering Society, Summer 2001.