Abstract :
The wide range of subjects, physics and engineering, physiology and psychology, coming within the purview of the illuminating engineer is pointed out. A brief résumé of the recent rapid progress in illumination is followed by a description of fundamental principles; in particular the use of the modern conception of luminous flux in illumination calculations is described. The chief requirements of a lighting system are that the lighting should be both adequate and suitable. It is pointed out that, in the past, adequacy has generally been emphasized to the neglect of suitability. It is, however, difficult to overestimate the importance of the latter factor in good lighting and it is dealt with in some detail under the following headings:¿ (a) Freedom from glare and excessive contrast in the field of view. (b) Adequate but not excessive diffusion. (c) Correct colour. (d) Correct proportion of local and general lighting. As an example of the application of the results of a psychological investigation to a practical lighting problem, a description is given of a method of so designing a street-lighting system that the glare may not exceed a certain specified limit. In conclusion the opinion is expressed that the present lighting load could be at least quadrupled, with immense benefit to the community.
