WHEN in the course of human Events, it becomes necessary….
Floating on the Frame Rate
byVanderleunonJuly 19, 2017
When reviewing the security footage from outside his house in Austin, Texas, Al Brooks spotted an unusual sight: a bird seems to hover past the camera with its wings completely stationary. Of course it wasn’t really hovering (and no, it’s not suspended by strings) but rather the frame rate of the camera matched the flaps of the bird’s wings perfectly resulting in a stroboscopic illusion. This is the same stroboscopic effect you might see in a video of airplane propellers that aren’t moving or when the wheels on a car appear to be frozen.
I would think that either the frame rate and wing flap was the same (1:1 ratio), or a perfectly divided ratio, 2:1, 3:1, or 1:3, 1:2, etc. That would create the same effect. Pretty cool regardless.
Anybody remember old cowboy movies where the stage coaches were being chased by bad guys and the wheels appeared to be rotating backward? I was just a kid when my Dad tried to explain the sample rate to me, but it did not jell until electronics school.
Phil in EnglewoodJuly 19, 2017, 3:45 PM
This video demonstrating/explaining rolling shutter is pretty good, too. The odd video of airplane propellers starting about 2:00 is particularly interesting.
“From a student radical/hippie/leftist of the Free Speech Movement/Vietnam Day Commitee era and a full-on Democratic Liberal in the decades after, I think I’ve evolved a politics that is neither right nor left but is, in its elemental nature, draconian. In the last 20 years, I’ve taken apart my beliefs with a sledgehammer. Now I’ve got to put the surviving parts back together with tweezers and other ‘shabby equipment, always deteriorating’.”
When reviewing the security footage from outside his house in Austin, Texas, Al Brooks spotted an unusual sight: a bird seems to hover past the camera with its wings completely stationary. Of course it wasn’t really hovering (and no, it’s not suspended by strings) but rather the frame rate of the camera matched the flaps of the bird’s wings perfectly resulting in a stroboscopic illusion. This is the same stroboscopic effect you might see in a video of airplane propellers that aren’t moving or when the wheels on a car appear to be frozen.
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I would think that either the frame rate and wing flap was the same (1:1 ratio), or a perfectly divided ratio, 2:1, 3:1, or 1:3, 1:2, etc. That would create the same effect. Pretty cool regardless.
Anybody remember old cowboy movies where the stage coaches were being chased by bad guys and the wheels appeared to be rotating backward? I was just a kid when my Dad tried to explain the sample rate to me, but it did not jell until electronics school.
This video demonstrating/explaining rolling shutter is pretty good, too. The odd video of airplane propellers starting about 2:00 is particularly interesting.
https://youtu.be/dNVtMmLlnoE