Stare at the red dot. The left side is blindingly white, the right is black.
Luminance Adaptation Illusion
A foundational look at light adaptation and biological gain control.
🧐 What do you see?▼
Stare at the red dot for 30s. The left side is pure white, the right side is pure black. Switch to the test phase. The gray square on the left will look darker, and the gray square on the right will look lighter, even though they are exactly the same shade of gray (#999).
🧠 Why this works▼
This is the Light Adaptation Aftereffect. Your photoreceptors (rods and cones) and horizontal cells in the retina adjust their sensitivity based on the incoming photon count.
On the white side, your cells have used up their chemical 'bleach' and have reduced their sensitivity significantly. When shown a medium gray, they respond poorly, making it look 'dim' or 'dark'. On the black side, the cells are 'super-sensitive', so they react strongly to even a medium gray, making it look 'bright' or 'glowing'.
🧪 Try variations▼
- Intensity: Use the intensity slider to change how bright the 'white' side is. Lower intensity will lead to a weaker aftereffect.
- Reset: Look away at a dark corner of the room to quickly 'reset' your retinal sensitivity.
❓ FAQ▼
Is this related to 'night vision'?
Yes. This is the exact mechanism that causes temporary blindness when you walk into a dark room from the sunlight—your eyes are in 'low sensitivity' mode.