Visual Perceptions under Modern Conditions

Abstract

The paper describes how certain topical problems of practical illumination strike a physiologist. Controlled investigations on the level of illumination, on the general illumination and on glare are described. The evidence is, on the whole, in favour of a high illumination without extremes of contrast. It is easy to find experimental evidence of improvement in vision when the illumination is raised to high values or when the worst forms of glare are eliminated. Modern practice aims at an illumination giving low contrast and with a minimum of glare. It may not be possible to justify the practice on experimental grounds but general considerations are in its favour. When contrasts are small the eye demands a higher general level of illumination than when strong contrasts are present. Although it is convenient to separate quantity and quality of light in controlled investigations there is probably a biological link between them. Some aspects of the colour of artificial illuminants are considered.