title: Luminance-brightness comparisons of LED alpha-numeric sources at suprathreshold levels.
abstract: An experiment was conducted in which observers adjusted the luminance of  2856 K white comparison source to appear equally as bright as a red, yellow, or yellowish-green LED alpha-numeric source. Although the present CIE photometric system predicts brightness-luminance ratios of 1.0, the ratios obtained in this experiment, for the mean observer, were 1.13 for the yellowish-green, 1.28 for the yellow, and 2.54 for the red. These results demonstrate that there can be substantial differences between photometric luminance based on the V(lambda) function and brightness as perceived visually.
mesh_terms: D000328:Adult; D006801:Humans; D008163:Luminescent Measurements; D008875:Middle Aged; D012684:Sensory Thresholds; D014785:Vision, Ocular / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology