The relative energy distributions of the M-2, P-25, AG-1, and M-3 flashbulbs have been determined over the spectral range from 3400 Å to 7600 Å, using a National Bureau of Standards lamp as a spectral standard, and a Jarrell-Ash Ebert-mount spectrograph as a spectroradiometer. From these data and the blackbody radiation function, values for the color temperature of the flashbulbs have been calculated using a computer to derive a least-squares, best-fit value of color temperature.
D. J. Bracco and S. Weisberger, "Determination of the Spectral Emission of Commercial Flashbulbs by Emission Spectrographic Techniques," Appl. Opt. 5, 1275-1279 (1966)