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06-24-2015 12:47 PM  4 years ago
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T 3d

rrApprentice

Boston Mass

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Camera
What frame rate of a camera do I need to record a helicopter white out seeing the blades look slow motion
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06-24-2015 03:53 PM  4 years ago
Aaron29

rrProfessor

USA

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Am curious about this, too. Seems your typical go-pro has a funny arc wiggling around where the blades were.

Also might be some application for full size airplane viewing out the front window. Similar RPM. Just about every vid I've seen with a gopro pointing out front has the funny spasming arc.

So, T3D, if you don't get your answer here, the full size guys who shoot cockpit videos might know?
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06-24-2015 10:18 PM  4 years ago
AirWolfRC

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42½ N, 83½ W

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The blades look like in slow motion because of stroboscopic effect.

The shutter speed is close to some multiple of the rotor speed.

You get a different strange effect when you use a camera with a rolling shutter. The blades look like they have turned to limp spaghetti.
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06-24-2015 11:04 PM  4 years ago
rexxigpilot

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rexxig2@comcast.net

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Could use a camera with a CCD photo sensor to get rid of the rolling shutter issue, but CCD cameras are mostly a thing of the past and expensive.

A very fast shutter speed can make the blades appear stopped, but most cameras can't operate that quickly at their fastest speed. For instance, to make a 600 size heli with a head speed of 2300 RPM appear almost still (1" of blade tip movement over the shutter open time) requires 1/6400 second shutter. My Sony NEX 7 only goes to 1/4000 shutter speed. So 1.6" of tip movement is what I can achieve with good light and around an F2.8 lens or larger.
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06-24-2015 11:05 PM  4 years ago
Cobra 46

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Cambridge il usa

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Ok here's what I'm thinking
1900 rpm / by 60 (seconds in a min )

At 1/60 sec. shutter speed, each blade will make half a revolution, creating a full disk. At 125 = 1/2 disk. 250 = 1/4 disk. Even at a shutter speed of 1/1000 each blade will move 22.5 degrees of a 360 degree disk, still showing some blur. You will have to most likely use a really fast shutter speed to stop the rotor blades. Check your max shutter speed on your camera.
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06-25-2015 02:12 AM  4 years ago
AirWolfRC

rrProfessor

42½ N, 83½ W

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It sounds like you guys are using still camera settings for calculations.

I thought we were talking motion video.

With 1800 RPM rotor speed on a two blade rotor and a video frame rate of 60 fps, you get rotors that look like they're standing still. Like using a stroboscope.

A little bit higher head speed and the rotors look like they're moving forward real slow.

A little bit lower head speed and the rotors look like they're moving backward real slow.
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06-25-2015 03:24 AM  4 years ago
turboomni

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East of the Equator

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Just like an old mechanical head speed tach. A spinning motor and a disc with holes in it spinning.Setup is everything, All my heli's can fly far better than I can pilot them
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06-25-2015 03:32 AM  4 years ago
Aaron29

rrProfessor

USA

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06-25-2015 04:19 AM  4 years ago
Cobra 46

rrKey Veteran

Cambridge il usa

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I wasn't sure what he wanted
I just through it out there if he needed it!
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