Brightness of a Capacitor Discharge Lamp - Bloch's Law for Brief Flashes
ARMY MEDICAL RESEARCH LAB FORT KNOX KY
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Brightness of a capacitor discharge lamp tc, 16-25 micro sec has been extrapolated from determinations of the subjective attenuation of comparable durations upon square wave flashes from a glow modulator tube R1131C. For the large field 61 degrees and high adaptation state 273 td, psychophysical integration of time and intensity Blochs Law was found to hold only at durations less than 1.5 x 1000 microsec. Examination of the manufacturers data on lamp candlepower converted to trolands encourages the conclusion that large errors occur when the troland and other photometric quantities remain uncorrected for Blochs Law effects which are found at short durations. A correct troland or adequate troland is described.