A simple and inexpensive 4pi light collector and two designs for a light meter for light attenuation studies

SUMMARY. A simple 4π light collector is described suitable for light attenuation studies. It uses table tennis balls as light collectors and its spherical response is near to ideal. A circuit for a simple meter based on an operational amplifier is given as well as that for a direct-reading log-ratio meter. Both circuits are intended for use with selenium photocells. The cost of the materials for detector and simple meter is less than £30.