84 Optical Illusions & Visual Phenomena 
(Visual Illusion · Optische Täuschung)

Motion & Time

• »Stepping feet« illusion 1 – strong, beautiful and (relatively) easy to understand
• Motion Induced Blindness – an illusion of disappearing dots
• Stereokinetic Phenomenon – an optical illusion of 3D from motion (aka »kinetic depth effect«)
• »Rotating Snake« Illusion – with a new explanatory twist
• Snake ad lib – optimising this motion illusion
• Pinna-Brelstaff Illusion
• Motion Aftereffect – also known as »waterfall effect«
• Spiral Motion Aftereffect – more effective for some
• Roget's Palisade Illusion
• Spoke Illusion – a motion illusion + an unexpected (?) aftereffect
• Wagon-wheel effect – closely related to stroboscopic artifacts
• Stroboscopic Artifacts – making a teaching point out of a nuisance
• Sigma Motion – an optical illusion due to an interaction of image dynamics and eye movements
• Eye Jitter – more on eye movements, involuntary ones
• Biological Motion – for me the most beautiful class of visual illusions
• Flash-lag Effect – moving and stationary objects perceived at different times
• Ramp Aftereffect – an aftereffect in time
• Enigma by Isia Leviant
• Freezing Rotation Illusion – a “Best Illusion of the Year” winner
• Reverse Phi Motion – something for the specialist
• »Stepping feet« illusion 2 – radial version of »Stepping feet 1«, weaker
• Motion-Bounce Illusion – sound influencing perception of motion (crossmodally)
• Motion Binding
• Breathing Square
• Missing-fundamental motion inversio
• Frequency-doubling illusion
• »Kaleidoscope Motion« Illusion
• Ternus Display
• Stroboscopic alternative motion

Luminance & Contrast

• Hermann’s Grid – fleeting luminance illusions
• Hermann’s Grid bent – a new twist, refuting the classical explanation
• Scintillating Grid – strong fleeting luminance illusions
• Induced grating – classical brightness contrast
• Craik-O’Brien-Cornsweet – collaboration of retina & cortex
• Wertheimer-Koffka-Ring – pitting Gestalt vs. lateral inhibition
• Simultaneous Contrast – here dynamic
• Pyramid Illusion – Vasarely revealed
• Munker-White Illusion – contrary to lateral inhibition
• Adelson’s »Corrugated Plaid« – context affecting brightness
• Adelson’s »Checker Shadow« illusion – more context affecting brightness
• Contrast Constancy – demonstrating space-average-based contrast gain control
• Contrast Gain Control – demonstrating temporal contrast gain control
• Lazy Shadow – Interaction of luminance & time
• Visual Acuity ↔ Hyperacuity

Colour

• »Lilac Chaser« – a rapid aftereffect, colours move which aren't really there
• Benham’s Top – colour from spatio-temporal patterns
• Neon Colour Spreading
• Structure from motion – fails at equiluminance
• Gestalt loss in equilumance
• Colour mixing – additive and multiplicative

Geometric- & Angle Illusions

• Hering Illusion – and other angular interactions
• Poggendorff Illusion – a classical geometric optical illusion with a new twist
• Fraser’s Spiral
• »Café Wall« Illusion
• Triangle Puzzle – a puzzle, but an illusion too

Space, 3D & Size Constancy

• Müller-Lyer Illusion – test your bisection accuracy
• Moon illusion
• T-illusion
• Sine Illusion
• Luminance Looming
• Shepard’s “Turning the Tables”
• Shepard’s “Subterranean Terror”
• Reverspective – reverse perspective
• Necker Cube – the mother of reversible figures
• Missing Corner Cube – a cube with multiple ambiguities
• Ambiguous Sillouette Illusion
• Frankfurter Illusion – binocular rivalry & supression

Cognitive- / Gestalt Effects

• Darwin Illusion – the afterimage creates a recognisable Gestalt
• Blur & picture content – spatial filtering (or high frequency masking)
• Hidden message – blur & figure-ground discrimination
• Kanizsa’s Triangle – depends on context
• Blotted letters – Gestalt completion
• Hidden Figures – Dalmatian Dog with 2 helpers
• Hidden Bird – more camouflage
• Rotation – changes the interpretation
• Impossible Objects – draw your own impossible object
• Hallucii – An “impossible” Movie

Specialties with faces

• Rotating face mask – hollow faces
• Find the Face (in the Beans) – a picture puzzle
• The face on Mars – imaginations of perception
• The »Thatcher Illusion« – inverted faces lose their emotional message
• »Ghostly Gaze« Illusion
• Dr. Angry and Mr. Smile – two messages in two spatial frequency bands
• The Lincoln Effect

Some sources

Donations

My bread-and-butter job: Universitäts-Augenklinik Freiburg

My involvement with our local →art society