Best Illusion of the Year Contest » Contrast

’Weaves’ and the Hermann Grid

admin — Sun, 13 May 2007 05:35:50 +0000

Kai Hamburger & Arthur Shapiro

University of Giessen, Germany, and Bucknell University, USA

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Swimmers, Eels and Other Gradient-Gradient Illusions

admin — Sun, 13 May 2007 05:34:04 +0000

Emily Knight & Arthur Shapiro

Bucknell University, USA

The red button adds/removes half of the background grating. The swimmers bob up and down when they are in front of the grating but not when they are in front of a uniform background

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Sinha: Hidden Strength of the Classical Simultaneous Contrast Illusion

admin — Tue, 09 May 2006 05:18:37 +0000

Pawan Sinha

MIT, USA

Catching Patches

admin — Tue, 09 May 2006 05:16:01 +0000

Rob Van Lier & Mark Vergeer

Radboud University Nijmegen, The Netherlands

We present an illusion based on Hermann-grid like gratings in which the contours are quite randomly distorted. These distortions guarantee a severe reduction or complete disappearance of the visibility of the patches. Starting with these gratings we show that the patches at the crossings return when luminance edges are introduced and extended at the intersections. The ‘returned’ patches have the same relative lightness properties as they would have in a regular Herman grid (dark patches when the crossing bands are relatively light, and light patches when the crossing bands are relatively dark). In addition, the polarity of the perceived lightness difference does not depend on the lightness of the edges (i.e., whether they are dark or light). A remarkable effect here is that at the crossings the whole area between the edges is perceived to have a different lightness, irrespective of the shape of that area (i.e., whether the edges bend inward or outward etc.).

See Power Point presentation with different versions of the illusion

World’s Largest Lightness Illusion

admin — Wed, 24 Aug 2005 05:05:29 +0000

Barton Anderson & Jonathan Winawer

University of South Wales, Australia & MIT, USA

In this illusion, it appears that there is one set of black figures and one set of white figures. In fact, the two sets of figures are exactly identical. They appear different because the surrounding regions they are on cause the visual system to segment the images into layers. Thus one set appears to be white figures behind dark clouds, and the other set appears to be dark figures behind light clouds. If you cut out the figures you will see that they are identical!

See the illusion: movie

Image segmentation and lightness perception Barton L. Anderson & Jonathan Winawer Nature. 2005. 434:79-83