Optimizing the strength of the Watercolor Effect by varying the width of the inducing contours. F Devinck1, P Gerardin2, M Dojat3, K Knoblauch2 |
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1University of Rennes, France |
| When a dark chromatic contour surrounds a lighter chromatic contour, the lighter color will assimilate over the entire enclosed area. This is known as the Watercolor Effect (WCE). Here, we measured its strength using Maximum Likelihood Difference Scaling (MLDS) as a function of luminance elevation of the inner contour. Five contour widths ranging from 6-24 arcmin were tested in separate sessions. An observer was presented with 3 luminances (a, b, c) of the stimulus contour. The task was to choose whether the strength of the fill-in color of stimulus b was more similar to that of a or c. The strength of the phenomenon increases with luminance of the interior contour. A stronger WCE was observed for an intermediate contour width (15 arcmin) with a decrease in strength of color appearance as contour width increased or decreased. In a second experiment, a contour width of 15 arcmin was used with different ratios between the outer and inner contour. The strength of the filling-in color was reduced for unequal contour widths, suggesting that balance of widths plays an important role in the WCE. Our data suggest that the WCE is tuned for the size of the inducing contours. |
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