An Investigation of the Effective Intensity of Flashing Lights.
VIRGINIA UNIV CHARLOTTESVILLE DEPT OF PSYCHOLOGY
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The effective intensity of flashing lights was examined as a function of duration and area at threshold and suprathrehold illuminance levels and against different background luminances. In the first experiment the perceived brightness of a flashing point source of varying duration was equated to the brightness of a standard point source of a fixed duration. The intensity-time function obtained showed the well-known Broca-Sulzer effect only at suprathreshold levels. The data indicated that the maximum effect was found to occur at shorter durations with an increase in standard source illuminance. In the second experiment, the perceived brightness of a flashing light of fixed duration and varying area was equated to the brightness of a standard source of fixed area and duration. The intensity-area function obtained demonstrated a phenomenon which appeared analogous to the Broca-Sulzer effect, but in terms of area rather than time. The data indicated that brightness increased with area up to about 2 and then decreased between 5-7 after which brightness appeared to be independent of size. Author