That's some weird compression artifact...

Slow frame rate, I think.

Neither. The "shutter" speed actually looks to be around an effective 1/5000 of a second.
Normal video is 1/60. The distortion of the prop is not due to compression, but due to
how the image is scanned off of the sensor chip... sequentially, row by row, bottom to
top. That is, if it takes 1/5000 of a second to read each row of pixels, then multiply
that by 240 to 480 rows and you get 10 to 20 full frame images every second.

The position of the prop changes by a couple degrees by the time the next row of pixels up
on the chip is read by the camera's firmware. The result is the shearing, bending, and
floating pieces of the blades when the whole image is assembled. Very disconcerting since
we are all too accustomed to our human vision having analog motion blur. This visual
distortion is called Temporal Aliasing (digitally sampled 'stair-stepping' of time).

So Ron. What I'd like to see is how you mounted the camera. There was virtually no high
frequency vibration in that mount... very rigid. Impressive. Plus being that these
cheapo digital cameras are tapeless (record directly to flash memory as an mpeg 4 file),
there's no breakup of the picture due to tape-to-record head gaps from a vibrating tape.
Going to a better, high-end camcorder (even the best mini-DV), your picture is no doubt
going to go in the toilet of digital dropout and break up unless you use an external video
recorder appropriately vibration/shock mounted in the cockpit to prevent tape vibration
that separates it from the rotating head drum.

Dean Scott

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