Luminance — A Tutorial Paper

The usual engineering interpretation of luminance (photometric brightness), luminous intensity per unit projected area, is adequate for many applications. However, the basic definition involves a limit of two independent variables, area and solid angle. Luminance is luminous flux per unit projected area per unit solid angle. Using this definition it is possible to explain why meters never exactly measure luminance and to determine what functions of luminance produce the responses of luminance meters. — All meter measurements and practical applications of luminance involve some type of averaging process. Generally, this presents no problem. There are many cases, however, in which a precise definition of the average must be based on the application since two independent variables are involved. It is important to recognize when this is required. This is especially true in scientific applications and in the design and analysis of luminaires, light sources, projection systems, and other optical systems. Many different values of luminance can be used to describe a light source, and it is important to choose the appropriate definition for each use.

Print ISSN

0361-4573

Published

1968-10

Content type

Original Research

DOI

10.5594/J13629