The measurement they used in their research was the foot-candle
, or the amount of light put out by one candle, one foot away.
The IESNA recommends that lighting levels for open parking facilities be a minimum of 3 foot-candles
, with an average-to-minimum uniformity ratio not to exceed 4:1.
The problem is that when local TV wants to broadcast a basketball game, the 50 foot-candles
aren't always enough.
The existing lamps provided only 25 foot-candles
on the floor.
According to these recommendations, visual tasks requiring high contrast should have illuminance values of at least 20-50 foot-candles
(215-538 lux; Category D).
These levels ranged from .04 foot-candles
to .45 foot-candles
Throughout the store, lighting levels have been increased from the traditional a foot-candles
to 52 foot-candles
Having obtained the number of foot-candles
, the next step is to determine the spacing of the lamps and their height.
Apparently no one has studied this intriguing question, but we do know that the intensity of white light has to be at least 40 foot-candles
(lux), and that an average of 100 lux for 16 hours will stimulate body growth and milk production in dairy cattle.
"We'd re-lamp a section, and within six months, the foot-candles
would diminish by at least 50% due to dirt and dust."
For example in Normal Mode: 170,000 Lux or 17,000 foot-candles
of light is available, while in Turbo Mode illumination can be increased to 220,000 Lux or 22,000 foot-candles
The Traceable light meter pen reads from 0 to 1,860 foot-candles
with a resolution of 0.1, and from 0 to 20,000 Lux with a resolution of 1.