EncycloZine

Clash

The alternating gradients cause the parallel vertical lines to appear to diverge.

Hermann's Grid

Ghostly black patches appear at the white intersections. The illusion was noted by Hermann (1870) while reading a book on sound by Tyndall (1869).

Shimmera

The blurry dots shimmer and twinkle (better in larger version).

Scintillating Grid

Black phantom dots randomly appear in the white circles. When focusing attention on a single white dot, some gray dots nearby and some black dots a little further away also seem to appear. More black dots seem to appear as the eye is scanned across the image (as opposed to focusing on a single point).

The illusion seems to be reduced when the head is cocked at a 45° angle. It appears only at intermediate distances; if the eye is moved very close to or very far away from the grid, the phantom black dots do not appear.

The illusion was discovered by E. Lingelbach in 1994. It is a variant of the Hermann grid illusion (see above).