Open AccessThe photo-electric measurement of the diurnal and seasonal variations in daylight and a globe intergrating photometer
Author(s) -
W. R. G. Atkins,
H. H. Poole
Publication year - 1936
Publication title -
philosophical transactions of the royal society of london. series a, mathematical and physical sciences
Language(s) - English
Resource type - Journals
eISSN - 2054-0272
pISSN - 0080-4614
DOI - 10.1098/rsta.1936.0003
Subject(s) - daylight , photometer , measure (data warehouse) , spectral composition , optics , environmental science , radiation , computer science , remote sensing , physics , geography , database
Photo-electric cells of various types are becoming more widely used every day for the measurement of illumination, both natural and artificial. Their great convenience renders them specially suitable for the measurement and recording of daylight. A word of warning is, however, necessary. What the cells measure is not really “ light,”i.e. , the physiological effect produced on the eye by the radiation, but rather the physical effect produced on the cell by the same radiation. It has been argued with some justice that it is therefore unscientific to use the ordinary units, derived from visual measurements, to measure the effect on the cell. The argument would carry more weight if these units were strictly limited to the measurement of illuminations of definite spectral composition, and so did not attempt to compare effects which are essentially dissimilar. For practical convenience, however, we are driven to measure in “ candlepower ” illuminants differing widely from the standard candle in spectral composition.