Tungsten lamps are now used very extensively in photographic sensitometry, and the wide range of exposure required for various materials makes necessary the accumulation of complete data on lamps of many sizes.
The characteristics of all tungsten incandescent lamps are similar in form, and in this note are described the average characteristics found for twenty lamps frequently used in this work.
From a study of the slope of the straight line, best representing the average candlepowercolor temperature relation, it is concluded that the changes in candlepower and color temperature, resulting from a small change in voltage, should be about equally perceptible under good conditions of observation.
K. S. WEAVER and H. E. HUSSONG, "A Note on the Color Temperature-Candlepower Characteristic of Tungsten Lamps," J. Opt. Soc. Am. 29, 16-19 (1939)