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<blockquote data-quote="barticus" data-source="post: 2219047" data-attributes="member: 778051">Yes.&nbsp; It&#039;s something called &quot;aliasing&quot;.I&#039;ll try to explain this with a very simple example.&nbsp; Suppose you&#039;re filming a wheel that has no features except for the air valve, which is at the 12 o&#039;clock position at the start.&nbsp; If the wheel turns clockwise at 24 revolutions per second (rps) and you film it at the rate of 24 frames per second.&nbsp; In a case like this, the air nozzle won&#039;t seem to move at all.Now suppose the wheel turns a bit slower, say clockwise 23 rps.&nbsp; Then the film will show the air valve moving CONTER-clockwise at maybe 1 rps.&nbsp; That&#039;s the reverse turning you&#039;re talking about.&nbsp; If, on the other hand, the wheel turned clockwise at 25 rps.&nbsp; They you&#039;ll see the air valve turning clockwise at about 1 rps.When you see wheels turning in reverse, you&#039;re probably seeing the wheel lug nuts or cut slots in the rims.&nbsp; That&#039;s a bit more complicated because the you&#039;re probably not tracking the same feature.&nbsp; In other words, if a wheel has 5 slots, A through E, and is turning clockwise really fast, you&#039;re probably not seeing the same slot from one frame to the next.&nbsp; If A is at 12 o&#039;clock in frame 1, B might be just short of 12 o&#039;clock in frame 2, then C a little short of that in frame 3, and so on.&nbsp; The wheel is indeed turning clockwise, but it&#039;s moving so fast the camera can&#039;t keep up with it.&nbsp; Since all the slots look the same, it looks like the wheel is turning in reverse.Hope that helps!</blockquote>

[QUOTE="barticus, post: 2219047, member: 778051"] Yes. It's something called "aliasing". I'll try to explain this with a very simple example. Suppose you're filming a wheel that has no features except for the air valve, which is at the 12 o'clock position at the start. If the wheel turns clockwise at 24 revolutions per second (rps) and you film it at the rate of 24 frames per second. In a case like this, the air nozzle won't seem to move at all. Now suppose the wheel turns a bit slower, say clockwise 23 rps. Then the film will show the air valve moving CONTER-clockwise at maybe 1 rps. That's the reverse turning you're talking about. If, on the other hand, the wheel turned clockwise at 25 rps. They you'll see the air valve turning clockwise at about 1 rps. When you see wheels turning in reverse, you're probably seeing the wheel lug nuts or cut slots in the rims. That's a bit more complicated because the you're probably not tracking the same feature. In other words, if a wheel has 5 slots, A through E, and is turning clockwise really fast, you're probably not seeing the same slot from one frame to the next. If A is at 12 o'clock in frame 1, B might be just short of 12 o'clock in frame 2, then C a little short of that in frame 3, and so on. The wheel is indeed turning clockwise, but it's moving so fast the camera can't keep up with it. Since all the slots look the same, it looks like the wheel is turning in reverse. Hope that helps! [/QUOTE]

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