David Novick's Color Illusion Page: Odds and Ends

This page rounds up various things I've tried with color and contrast illusions.

Experiment with Munker illusions: a single oval that appears to have a green-blue gradient. In fact the oval is a uniform color.
Much of the effect may be due not to color but to light-dark contrast.
So here's an example where the foreground and background colors have similar luminance. This means that the effect of non-uniform color in the oval is due to Munker rather than brightness contrast.
Having a significant brightness contrast definitely makes the illusion stronger, though.
An experiment with contrast illusions: As a baseline, here's a basic contrast illusion. The central rectangle on the left looks darker than that on the right, even though they're actually the same shade.
Having the shade gray vary within the central rectangles does not diminish the illusion, at least if, as in this case, the center of the rectangle is lighter. If anything, the illusion is stronger.
But varying the shade within the central rectangle a lot, in this case with a photo of cat, seems to destroy the illusion completely. To me, both photos look identical.

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Department of Engineering Education and Leadership | The University of Texas at El Paso

May 18, 2018