Experiment · persistence of vision
Persistent vision
A moving image does not wait for your eye: your eye keeps drawing after the screen stops. This piece makes that persistence first-person — you resolve a spinning pattern into a gray blur, then hold its ghost on a page that has gone blank.
The stage
Fuse it, then vanish it
Spinning at 60Hz sector rate — your eye is already fusing the spokes into gray.
Sector frequency: 60 Hz
Fix your gaze on the center dot. After the countdown the ring disappears — keep staring where it was. The shape you still see is drawn by your retina, not by the page. The faint ghost the stage draws afterwards is only a guide to where to look.
The reveal
The screen stopped. You didn't.
An afterimage is the visible tail of persistence. Stare at a high-contrast shape for several seconds and the photoreceptors beneath it adapt to it; when the shape leaves, the patch of retina around it keeps reporting the difference for a moment. The ring you still see is not on the page — on a blank page you can actually catch it, its polarity inverted, floating where the ring was.
The ghost the stage draws is fainter than the one your eye makes, on purpose. It marks where to look without competing with what your own retina produces. Go ahead and blink: the real afterimage rides out a blink, and is gone by the second one.
How it works
Persistence, in two senses
Persistence of vision is a nickname for two real things. The first is temporal fusion: above roughly 50–60 cycles per second the eye stops resolving events and reports their average. That is why the spinning sectors collapse into a gray disc as you raise the speed, and why the sector frequency readout matters — a boundary passing a point N times a second is the same arithmetic as a flickering light.
The second is adaptation. Hold one image on the retina long enough and the cells serving it stop responding, so when the image goes, the surrounding cells briefly over-report. The ghost is compensation for the blank: the shape you saw, subtracted from the white page your eye expects.