This question is answered by Bill Plageman, vice president of marketing and product management at Amerlux.
There is no difference between foot candles and lux in respect of what they measure.
In the same way that feet, inches and metres both measure length, foot-candles and lux both measure the illuminance (the amount of light) that falls onto a surface.
The footcandle is an ‘imperial measurement’, while lux is a metric (or SI) measurement.
What is the difference between the two figures?
Footcandles are more or less ten times the equivalent lux measurement, which comes from the way that the light is measured.
Take a beam of light and measure its intensity at one foot away from the source and that will give you the foot candle reading. Take the same beam of light and measure it from one metre away from the source and that will give you the lux measurement.
One footcandle equals 10.764 lux.
One lux equals 0.09 ftc.