Thirty photos of a quiet street are thirty witnesses. Twenty-nine agree. One swears a cyclist was in the middle of the road.

Average their stories and you get a ghost cyclist, which is worse than either. Averages are easily bullied. The middle answer isn't: line up all thirty versions of a pixel, darkest to lightest, and take the one in the middle. The cyclist can shout all he likes; he's at the end of the queue, and the end of the queue never wins. Anyone whose story strays too far is no longer listened to at all: the statistical version of not being invited to the pub.

The catch: witnesses only agree if they were looking at the same spot, and you held the camera like a person. Near things wobble more than far things (hold up a finger and sway your head), so no single nudge lines up the bush and the hills. Each frame is bent, patch by patch, until every leaf agrees. Then they vote.

And the cyclist? Outvoted twenty-nine to one, he was never there. Somewhere a man is pedalling home with no idea he's been removed from history by a show of hands.

He's in good company. In 1838 Daguerre photographed the Boulevard du Temple, one of the busiest streets in Paris, and it came out empty: the exposure took minutes, and everything that moved simply failed to register. Everything except one man, standing still to have his boots polished, who became the first person ever photographed. Not because he mattered, but because he didn't move.

Combine runs on the same rule. Stand still and the picture keeps you. Keep moving and the crowd votes you out.
