footlambert

The footlambert is a unit of luminance, a measure of how much light is reflected or emitted from a surface. It is part of the imperial and U.S. customary systems of measurement. One footlambert is defined as the luminance of a surface that emits or reflects one lumen per square foot. In other words, if a surface has a luminance of 1 footlambert, it means that for every square foot of that surface, one lumen of light is being perceived.

This unit is commonly used in the lighting industry, particularly in the United States, to specify the brightness of displays, screens, and illuminated signs. For example, the recommended luminance for a television screen in a darkened room might be around 10 to 30 footlamberts, while a brightly lit office might aim for 50 to 100 footlamberts.

The footlambert is related to other units of luminance, such as the candela per square meter (cd/m²), which is the SI (International System of Units) standard. One footlambert is approximately equal to 3.426 candela per square meter. This conversion is important for comparing luminance values across different measurement systems. While not as universally adopted as the candela per square meter, the footlambert remains a relevant unit in certain professional contexts.