Fig 6. Same as Fig 2 for data from three sources.

First, observer AR replotted from Figure 2 of Rovamo et al. [18] measured using a white 1.66° diameter flickering target inside a 3.32° diameter equiluminant white surround. Second, observers WS and TU replotted from Figure 2 in Swanson et al. [19] measured using a 2° diameter flickering target illuminated by a mixture of red and green LEDs (light-emitting-diodes) that appeared metameric with a 600-nm light. Third, observers VMC and TEW replotted from Figure 2 in von Wiegand et al. [20] measured using a flickering LED target with a dominant wavelength of 625-nm that extended to 1° diameter and then fell with a cosine intensity profile to zero intensity by 2° centred within a larger 18° diameter annular surround of the same mean luminance and chromaticity. Both were superimposed on an 18° diameter 565-nm background intended to suppress rods.