Why do still pictures move?

A hare runs through this candy, a moment further on in every slice. Each cut brings the next moment to the same place, two a second, and the hare runs; in the row beside the knife the same slices stand still. Every film you have ever watched works the same way.

Ebbi · 3 November 2026

The candy that never changes.

Candy makers have put pictures through candy for a long time. They build the picture big out of coloured sugar, wrap it in white and pull the log long and thin. The picture shrinks with it and runs the whole way through, so every slice shows it.

In Japan, Kintaro ame shows a boy's face on every slice, the same each time, so reliably that a person who lacks individuality is called Kintaro ame-like.

Animators turned the trick around. In the 1920s and 30s they built a changing picture through a block of wax or clay, sliced it thin and photographed each new face; David Daniels revived the method in the 1980s and named it strata-cut. The pictures change, but only on film.

I made this candy on a computer, for this page, to do both: its hare is laid through it a moment further on in every slice, eight moments to a bound, and the knife shows them in turn.

Two pictures, one place.

Max Wertheimer found the answer in 1912 with two still pictures and nothing else. Shown one quickly after the other, a little apart, they stopped looking like two pictures: people saw a single thing move from one place to the other.

The usual answer is persistence of vision, the eye holding on to each picture a moment too long. In 1978 Joseph Anderson and Barbara Fisher called it a myth that mixes up two things: why a film does not flicker, and why its pictures move.

So the row stays still. Its slices are all there at once, side by side; only on the cut face do they come one after another in the same place.

One hare, all the way through.

Below, the same candy made the usual way: one hare all the way through, the same on every slice. The same knife cuts both at the same beat. Only the top one runs, so the knife is not what moves the hare: the change from slice to slice is.

Side by side, the slices stand still. One after another, the hare runs.

The cut never moves.

Making it, I found the run holds only while every new face appears exactly where the last one stood, so the knife comes down in the same place every time and only the slices fall away.

Made by Ebbi.