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Old Feb 02, 2011, 04:16 PM
NightRunner417 is offline
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Fly Like A Thing Posessed!
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USA, FL, Fort Myers
Joined Nov 2010
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Originally Posted by KeithLuneau View Post
That's pretty impressive how the prop disappears under the indoor light! I wish they would do that in the sunlight... lol
It's the light level... You can actually *make* it happen if you put a bit of tinted glass or optical quality plastic in front of the lens. See, in bright light, the electronic shutter of a digital camera has to switch very quickly in order to limit the exposure and keep everything from being too bright or even whiting out. The fast shutter times act like a strobelight, freezing objects in fast motion. That's why you see bands when looking through the prop - because the fast shutter is freezing the moving prop but in a distorted way due to the scanning action of the camera imager. Shutter rates on modern digital cameras can exceed 1/10000th of a second with ease, allowing even very fast objects to be frozen very cleanly in a still image.

In lower light, fast objects begin to blur because the shutter can no longer switch fast enough to cause the strobe effect. When light decreases sufficiently, any very fast moving object will blur so much that it's like looking at a fast fan with the naked eye - all you see is a kind of dimness to the light that passes through the fan blades, but you don't see the blades themselves unless you are looking at it under pulsating light like fluorescent, television glare, or incandescent lighting. Under daylight, you simply don't see them at all, you only see the blur.

If you want to eliminate the stripe effect in your videos of the prop and the shutter rate interfering with each other, simply slow down the shutter by dimming the light that it sees. The prop will blur out as a result. The downside of this is that if you don't get it right, like you darken the view TOO much or the light level drops due to clouds or whatever, even the relatively slow moving objects could begin to blur, causing a general motion blur across the entire view. Pick the right day, with steady light bright or dim, and you can exploit the effect and your prop will only look like a circle of blur, just like it does to your eyes. :-)

Rick NR417
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