Maintained footcandles indicates a light level after light loss factors are considered over a period of time. While light output may describe either the output of a light source or fixture, maintained footcandles always takes into account the efficiency of the fixture in transmitting light to the workplane. The light that we actually see, brightness can be measured as the light leaving a lamp, or the light reflecting from an object's surface. If not controlled, brightness can produce levels of glare that either impair or prevent a desired task being performed. Glare can be described as direct or reflected glare, which can then result in discomfort or disability.
Direct glare comes straight from the light source.
Reflected glare shows up on the task itself, such as a computer screen. Discomfort glare does not prevent seeing makes it uncomfortable. Disability glare prevents vision. Lighting systems require electrical input to work. A lighting system's rated input wattage, therefore, is the amount of power required for it to work at any given instant of time.