seeing things

[dlmfan]

since i been watching ppv, i see something that i don't understand. no matter what class, if the lettering is bright white on the tires, in the corner, the left rear shows it stops and goes reverse. what is the deal??

[Shiny Side Up 18]

It's an illusion. The camera's refresh rate is slower than the "refresh rate" of the human eye.

[BloomerWon]

Stroboscopic Effect. It's wagon wheeling...

[Morgs153]

Certain videos of helicopters and prop driven aircraft will do the same thing when the rotation of the prop and refresh rate synch up. There's a vid I watched of a TU95 Bear which has massive turbo prop engines and contra rotating twin props on each engine. Sometimes it looks like both quit turning.

[GrocMax]

Its because an electronic camera's 'aperture' scans vertically and from left to right, when the vertical refresh rate comes close to the 'beat frequency' (matching frequency or multiple) of the rotating object, it slows, stops, and reverses optically.

[EvelB7]

Try using an adjustable timing light if want to see how this happens...