Blur & figure-ground reversal

from Michael’s Visual Phenomena & Optical Illusions


What to see

Above you see –most probably– an apparently random array of blocks. Blurring the image reveals an unexpected message of doubtful soundness.

There are several ways of blurring: You can squint your eyes, move away from the screen, or use the sliders “Size” or “Blur” or both of the latter two. The most famous version is on page 2 (it’s not true, BTW :), and the effect has been turned into an advert for glasses (page 3)


The strong spatial low-pass filtering removes the 3-dimensional masking cues, enabling a re-evaluation of figure and ground.


I once saw this when I visited Spillmann’s lab, the animation above is based on an image I found as “eye test”. The original source seems unknown. Please step forward so I can acknowledge!