Brightness, when used by lighting fixture companies, is a term to describe the amount of light a person sees at the ceiling reflecting off the reflector trim. Generally the lower the brightness the better, making the fixture less noticeable in the ceiling. The terms Brightness and Luminance are used interchangeably, though Luminance is the more correct terminology, "brightness" is the more commonly used.

Brightness, or Luminance, is the light that is reflected from a surface toward the eyes, and which the eye perceives. Brightness can be determined two ways, either by calculation using the Average Brightness Method, or by direct measurement using the Maximum Brightness Method.

In the Average Brightness Method the luminance is calculated by using the candlepower measurements obtained from the test data and dividing by the area of the luminaire aperture at the specified angle.

In the Maximum Brightness Method the maximum luminance of the luminaire is measured directly with a brightness meter. The meter commonly views and records the brightness of one circular square inch.

The unit of measurement for brightness is the product of illuminance multiplied by the surface reflectance. Illuminance is the quantity of light (footcandles, lux) at a point on a surface. Brightness data is expressed either in footlamberts (the unit of luminance equal to 1 lumen uniformly reflected or emitted by an area of 1 square foot), or by candelas per square meter [cd/(m)(m)].

When comparing luminance data one needs to be aware of which method was used and with which unit of measurement. Candelas per square meter [cd/(m)(m)] can be converted to footlamberts by multiplying values by 0.2919. To convert footlamberts to candelas per square meter [cd/(m)(m)] multiply footlamberts by 3.426.