Abstract
When two images, one depicting colored disks and the other depicting colored windmill patterns, are displayed in succession, the color of the windmills is perceptually replaced by black. The illusion is striking. Experiments confirmed (1) that the luminance contrast between the target patterns and the background must be large and (2) that the disks and windmills must be static on the retina and in register. The illusion is weakened when the windmills and disks have different colors.
Highlights
We studied some characteristics of this illusion as follows. (1) The illusion was strong when the background of the windmill was bright (Figure 2a). (2) The disks and windmills had to have the same color, otherwise the illusion was weak (Figure 2a). (3) The desaturation was maximized when the windmills appear immediately after the disks without temporal gap (Figure 2b). (4) The illusion strongly depended on the luminance of the windmills and their background, while it depended only weakly on the hues in the pattern (Figures 2c and d)
Dark patterns and bright backgrounds led to the stronger desaturation
The other characteristics based on our personal observation are that (7) the shape of target other than the windmill, e.g., concentric circle or random dots, can induce the illusion, as long as the background region weaved into the figure, and (8) the smaller masks relative to the windmills appear to decrease the illusion, which suggests that the masks need to cover the whole region of the windmills
Summary
We studied some characteristics of this illusion as follows. (1) The illusion was strong when the background of the windmill was bright (Figure 2a). (2) The disks and windmills had to have the same color, otherwise the illusion was weak (Figure 2a). (3) The desaturation was maximized when the windmills appear immediately after the disks without temporal gap (Figure 2b). (4) The illusion strongly depended on the luminance of the windmills and their background, while it depended only weakly on the hues in the pattern (Figures 2c and d). We report a novel optical illusion wherein chromatic windmills are perceptually replaced by black when presented in succession with chromatic disks (1) The illusion was strong when the background of the windmill was bright (Figure 2a).
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