David Novick's Color Illusion Page: Relationship between Color-Completion and Munker Illusions

This page explores the relationship between the color-completion illusion and the Munker illusion.

As a warm-up, notice that Munker illusion may be a function of the foreground color only: the illusion persists when the background changes to gray.
And here's a similar example with red and blue. All four ovals are actually the same color..
In this green-violet example, the illusory colors look similar whether the background colors are the opposites or just gray.
If the oval color is white, completion and Munker effects appear to be identical. The two illusions are basically the same. Any difference is likely a brightness contrast effect.
Indeed, changing oval to gray (RGB 123,123,123) produces difference, especially for green, that is likely due entirely to brightness contrast effect. But main idea is that Munker represents spreading completion color over oval's color to create illusory color.
Here are the same foreground/background colors with yellow ovals. Again, the color-completion and Munker illusions appear to be nearly identical.
The same colors with darker yellow ovals produce similar results, although to my eyes in this case there are slightly larger differences between the completion and Munker colors.
With light-blue ovals, the result is again similar. The ovals are, of course, all the same color.
With darker blue ovals, the effect is mostly similar but the greenish ovals seem to differ in color between the Munker and color-completion cases. I expect that this difference is due to the brightness contrast effect.
Indeed, changing the background color to a lighter gray for the greenish blue oval in the color-completion case seems to make the completion again more similar to the Munker case.
Here's a strong example of how the Munker and color-completion illusions are basically the same. In this Munker illusion, the ovals are actually the same shade of yellow.
And here's the same Munker illusion with its corresponding color-completion illusion, where the background is the same yellow as in the Munker illusion. I perceive the ovals in the Munker illusion to be exactly the same colors as the in the color completion illusion.
One more thought on Munker and color-completion illusions: it doesn't always work. For example, here's a Munker illusion where the ovals are both gray, and they appear to be strongly reddish and greenish.
And yet in a color-completion illusion with the same green and violet foreground colors but with a light gray background, to my eyes the ovals now look just mainly gray rather than reddish or greenish, and I'm not sure why this is the case.

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

May 17, 2018