Hermann grid illusion
Watch grey smudges appear where bright streets cross
The Hermann grid produces phantom dark spots at intersections when your retina adapts to high-contrast “streets”. Begin by narrowing the streets, then scroll to expand the full lab.
Live canvas
Step 1 · Street width
Make the white streets narrow or wide
Thin white corridors between black squares trigger the strongest grey blobs. Widen the streets and the illusion fades away.
Step 2 · Contrast
Dial in the dark square levels or invert the entire grid
High contrast exaggerates the response from retinal ganglion cells. Softening the dark squares or inverting the palette lets you test how polarity influences the effect.
Step 3 · Geometry
Control the grid size and the corners
More cells create more intersections to explore. Slight corner rounding morphs the illusion toward the Scintillating Grid variant.
Step 4 · Extras
Add blur or scintillating dots
Soft defocus mimics viewing the grid slightly out of focus. Adding small white dots at intersections morphs the classic illusion into its scintillating cousin.
Step 5 · Presets & export
Jump to proven configurations or save a snapshot
Use presets to demonstrate strong and weak variants in class, then export a PNG or SVG when you find a setup you like.