What is the basic measure of the amount of light produced by a light source?

The basic measure of the amount of light produced by a light source is referred to as luminous flux, which is measured in lumens. Lumens quantify the total amount of visible light emitted by a source in all directions, providing a clear indication of its brightness. This measurement is fundamental in the field of lighting and is crucial for understanding how much illumination a source can provide in a given space.

In contrast, watts measure electrical power consumption rather than light output, which is why this choice is not suitable. Lux and footcandles, while related to the perception of light in a specific area, are measures of illumination, representing light intensity per unit area. Lux is defined as one lumen per square meter, and footcandle is one lumen per square foot. However, they do not measure the total output of a light source itself but rather how that light is distributed over a given area. Thus, lumens stand out as the correct choice for measuring the light emitted by a source.