Abstract: Brightness match of a white light and a low frequency monochromatic light, one of which was time modulated and presented intermittently, wasade by observers on a two-channel optical system. In order to match a con-stant white light, when the light/dark ratio of the monochromatic lightwas 16/4, its average brightness was lower than a constant monochromaticlight, independent of wavelength. This shows that the Talbort-Plateau lawdoes not hold for low frequency high light/dark ratio intermittent monochro-matic lights. The Talbort-Plateau law is effective for intermittent monochr-omatic lights of 650 nm. at low light/dark ratio(4/16 and 8/12).

Key words: Brightness sensitivity, Monochromatic light, Light/dark ratio, Brightness match