March 5, 2017

Watch: This Is What Happens When You Sync Your Frame Rate with a Helicopter Rotor

No, it's not a magic trick. It's just clever cinematography.

If you perfectly sync your camera's frame rate with the rotation of a helicopter's rotor, some pretty interesting things happen. YouTuber Chris Chris has shared a video that shows a helicopter taking off, which sounds like nothing special, but because the camera that captured the scene had all the right settings, the blades of the aircraft appear to be completely still. Check out this crazy video below:

If you're wondering how this trickery works, it's actually relatively simple. The main source of confusion is whether it's the frame rate or shutter speed that makes the effect possible, but both are actually necessary to pull it off. In an online discussion about the phenomenon, an anonymous reader broke it down: 

It’s a factor of both. Since each frame has to ensure the blade is in the same position as the last it therefore needs to be in sync with the rpm of the rotor blades. Shutter speed then needs to be fast enough to freeze the blade without too much motion blur within each frame. Here the rotor has five blades, now lets say the rpm of the rotor is 300. That means, per rotation, a blade is in a specific spot on five counts. That gives us an effective rpm of 1500. 1500rpm / 60secs = 25. Therefore shooting at 25fps will ensure the rotor blades are shot in the same position every frame. Each frame then has to be shot at a fast enough shutter speed to freeze the blade for minimal motion blur.

This weird effect isn't anything new. There are quite a number of videos out there just like this.

And if that wasn't cool enough for you, here's a video that uses the same technique to create the illusion that a stream of water is frozen in time.

Your Comment

8 Comments

There are people out there thinking about rotation rate, shutter speed, and frame rate to capture the illusion of a floating helicopter, that's impressive. Could one achieve the same effect by using a similar formula with car commercials e.g., the rotation spin on a tire rim?

Salud,

A.S.

March 5, 2017 at 10:15AM, Edited March 5, 10:22AM

2
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Absolutely. The "wagon wheel" effect.

March 5, 2017 at 10:38AM, Edited March 5, 10:38AM

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Dylan Sunshine Saliba
Cinematographer
86

Looked up "wagon wheel" effect, that makes sense. I figured digital vs film would have changed that effect, but it remains the same . . . still gotta lot to learn.

March 5, 2017 at 10:56AM

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March 5, 2017 at 1:27PM, Edited March 5, 1:27PM

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In my line of work you get laughed at if you come back with footage like this.

March 6, 2017 at 10:52AM, Edited March 6, 10:52AM

1
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i agree. Especially if you need to film rotating objects. Any tips on filming not to get this effect?

April 14, 2017 at 8:54AM

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That is so cool, I am trying to think of a practical application for doing this but I'm pulling a blank -.-

March 7, 2017 at 6:15AM

0
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Allison James
Dating specialist
1

Bring it into after effects or some other compositing software, trim off the blades & turn it into a space craft!

March 10, 2017 at 2:42PM

2
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Derek Armitage
Filmmaker & Vlogger
568