Understanding Foot-Lamberts and Footcandles: A Guide to Light Output Measurement

Foot-Lamberts (ft-Lm) is a unit of measurement for light output, and it is used to describe the brightness of displays and other light-emitting devices. It is defined as the amount of light emitted by a source in a given area, with one foot-Lambert being equal to one lumen per square foot.
Footcandles (fc) is an older unit of measurement that is similar to foot-Lamberts, but it is based on the amount of light emitted by a source in a given time period, rather than the total amount of light emitted over a given area. One footcandle is equal to one candela per square foot, where candela is a unit of measurement for luminous intensity.
Both foot-Lamberts and footcandles are used to describe the brightness of displays and other light-emitting devices, but they are not interchangeable units. Foot-Lamberts are used more commonly in the United States, while footcandles are used more commonly in Europe.