On Wed, 21 Feb 2007 10:03:46 -0500, "Dean A. Scott"
wrote:


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.

That makes sense. IIRC, there is a type of still-camera shutter that works
similarly, and you sometimes see the same kind of "arcing" of moving propellers.

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.

Beginner's luck. The cameras were basically mounted on an extension of a big
aluminum angle, which was clamped to the axle by hose clamps. I put piece of
inner-tube rubber under the angle/clamps to protect the paint of the axle.
Details, including photos, on:

http://www.bowersflybaby.com/pix/video.html

The one problem I have is a low-frequency shake of the image. If you watch the
ground in the distance, you can see it's shaking up and down at about a 1/2 to 1
Hz rate. Both cameras do it, the newer camera has electronic stabilization, and
it didn't seem to help.

My guess is that it's that bit of rubber that's protecting the axle...I think
the mount is "bouncing" a bit. The effect is not really visible with the old
camera when it was mounted atop the tail, where there isn't any rubber involved.

Gonna try to protect the axle with nylon or wood, instead.

Ron Wanttaja