LogFAQs > #932237378

Sahuagin posted...

pretty sure it's more related to compression and/or image stabilizing. I saw a similar effect watching a bicycle video where the front tire appeared to almost be motionless except for turning forward an inch or two once every few seconds. the speed of the tire should be fluctuating a lot, so it's not synchronized with the camera. the compression on the video is just reducing something that is otherwise super hard to compress due to the amount of noise involved into something extremely easy to compress since it's no longer moving frame to frame.

Compression wouldn't cause this at all. It's totally the video frame rate matching a specific rate of rotation of the object. A wheel with thirty-two spokes would be a lot easier to capture stroboscopic footage of than a helicopter with five propeller blades. You just need the frame rate to match a multiple of 1/32 the rotational speed of the wheel compared to a multiple of 1/5 the helicopter blades. There are many more opportunities to match the wheel compared to the helicopter. Even if you don't match the rotational speed, the video can still appear to show a very slowly moving rotating object if you get close to the ideal amount. The the wheel wasn't completely stationary as it progressed a couple inches every few seconds, so they weren't entirely synchronized to one of those multiples of the wheel.

Here's a related video on the stroboscopic effect:
https://www.youtube.com/watch?v=2SgG99QKLFE

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