Problems of Underwater Illumination

Abstract

Visibility and lighting problems under water are discussed in relation to the known properties of the medium. Measuring instruments for use on the actual location are described. A photographic method of examining the visibility problem in daylight was used and range curves for targets of different reflection factor in water of varying clarity are derived from contrast measurements. The requirements of artificial lighting in water of poor clarity have been studied, the necessary equipment using mercury and sodium vapour discharge lamps has been developed experimentally, and techniques of its use in the sea have been learnt. The use of high speed photography for some special underwater problems requires the use of flash discharge tubes, and the application of these to propeller cavitation research is described.