Abstract

A provisional observer for low level photometry is given by means of tables which show the relative spectral luminosity at luminance levels from the scotopic to the photopic regions. Derived tables show the spectral distribution of light from several Planckian or near Planckian sources, a Planckian radiator at 2360°K being used to define the illuminance scale.

Data are shown which indicate that a restricted additivity law, as herein defined, may be used at low luminance levels in evaluating stimuli of mixed spectral composition.

The I.C.I. standard photopic luminosity curve has been used as the terminal or photopic data in the formulation of this observer. However, data which have been accumulated in the 24 years since this luminosity function was adopted indicate that the blue-violet spectral region should be revised. The technique of low level photometry is discussed briefly.

© 1949 Optical Society of America

Standard Observer for Large-Field Photometry at any Level

D. A. Palmer
J. Opt. Soc. Am. 58(9) 1296-1299 (1968)

On the Standard Source for Low Level Photometry

J. Terrien
J. Opt. Soc. Am. 39(10) 888_1-889 (1949)

A Comparison of Electrical and Psychophysical Determinations of the Spectral Sensitivity of the Human Eye

Lorrin A. Riggs, Richard N. Berry, and Matthew Wayner
J. Opt. Soc. Am. 39(6) 427-436 (1949)

A Comparison of Direct Colorimetry of Titanium Pigments with Their Indirect Colorimetry Based on Spectrophotometry and a Standard Observer

Deane B. Judd
J. Opt. Soc. Am. 39(11) 945-950 (1949)

Sunlight and Skylight as Determinants of Photographic Exposure. II. Scene Structure, Directional Index, Photographic Efficiency of Daylight, Safety Factors, and Evaluation of Camera Exposure

Loyd A. Jones and H. R. Condit
J. Opt. Soc. Am. 39(2) 94-135 (1949)