Are Scotopic Lumens?
Published lumen ratings are based on the "photopic" lumen
("P"), or light measurement based on daytime observations.
Lumen measurements, corrected for nighttime vision, are known as "scotopic"
lumens ("S"). The ratio of light measured by the 2 methods
is called the "S/P ratio". The S/P ratio for white-blue
(5000K daylight) light sources is 2.1. At 4000K the ratio is 1.65,
and for HPS lamps the ratio is 0.64. As a result, 4000K light sources
are at least twice as effective for viewing at night and 5000K, at
least 3 times as effective as HPS sources at the same at the same
Lamps with high scotopic-content and high S/P ratios, such as Venture's
Natural White lamps, also improve the ability to see indoors. Human
studies have shown that the S/P values, though previously applicable
to only nighttime conditions, can be used to describe the "effective
lumens" of indoor lighting as well. For example, if two rooms
are lighted separately with 4000K and 5000K lamps to equal photopic
luminance, the 5000K room will appear 13% brighter (2.1/1.65)0.5
With Opti-Wave Ballasts
as a system for:
lamp lumen maintenance (90%!)
Improved ballast efficiency
Lower audible ballast noise
Compare the Spectrums
Natural White® 950 Series