The height of the fixture or lamp above the ground.

 

The general overall level of lighting in an area.

An opaque or translucent element to shield a light source from direct view.

A device used with a discharge lamp to obtain the necessary voltage, current, and/or wave form for starting and operating the lamp.

The angle between the two directions in the plane in which the intensity is equal to a given percentage (usually 10 percent) of the maximum beam intensity.

Strength of the sensation that results from viewing surfaces from which the light comes to the eye.