In lighting design there is a need for simple way of indicating how bright different surfaces will appear to the eye so that lighting designers may converse meaningfully with non-specialists in routine engineering situations. Scales of apparent brightness, which imply that the perception of brightness can be represented by a single figure combining both luminance and adaptation level, suffer from a number of shortcomings. The author suggests that a logarithmic scald of luminance while not accurately representing the human perception of, brightness, has a number of conveniences to commend its use in his way. It would also appear to be possible to extend the principle for the purpose of specifying the visual field, by employing a logarithmic scald of illumination which could be combined with a reflectance scale to provide a dual-scale.
Abstract