Helicopter Illusion

Interesting illusion: the helicopter's blades are somehow in sync with the camera's shutter making it seem as though they are not moving

Category:

Autos & Vehicles

Tags:

• helicopter
• illusion

[xarealpersonx]

God, are you people retarded? It's not a fake! The blades are just spinning at the same speed the camera is picking up.

[bumslug]

That's a MI-24 Hind helicopter. Rotor diameter 17.3m, rotation rate 240 rpm. If rotor spans ~70% of a 640x480 frame, we have ~4cm / pixel. For blur artifacts of +/- 1 pixel, blade tip travel ~10cm is allowed. The blade tip speed is 217m/s, so a 1/2000s exposure will satisfy this. Easily attainable in broad daylight with a good lens, and easily synced with a camera running at 1000-2000fps. In the last frame, the rotor tips are noticably less distinct than near the hub. That's motion blur.

[Doctopie]

@bumslug ....yeah

[jomdeluise]

Nyquist frequency Dumb Assholes

[lelliottjrUSMC]

What kind of butt-fucking sorcery is this???

[bumslug]

@Rapt0r111 Hi, thanks for your critique... That old comment was to address a bunch of silly reactions claiming the video is fake for all sorts of reasons. I thought I showed quite clearly why it's feasible to achieve this effect even with a simple approach of dropping the correct number of high-speed frames. There are other more clever ways to sync the shutter, such as triggering from the rotor sound. Also, I should point out that lift is generally achieved by altering blade pitch, not RPM.

[Rapt0r111]

@bumslug The only useful bit of information for explaining why this illusion occurs in your entire post is "240 rpm". Which could be completely incorrect for this video anyway due to the fact that if the blades constantly span at 240rpm there would be vertical acceleration possible.

[arandomJohn]

Note that the rate of rotation doesn't have to match the FPS of the camera. It just has to be some multiple of the camera's capture rate. In fact it gets worse than that. With the five blades it could be a different blade in a given position from frame to frame, so there are all sorts of framerates for the camera that could result in this effect.

[CLAV777]

@bumslug ..umm ya gotcha

[FactoryGaming]

@bumslug yeah i know..i totally agree

[drjeckyller]

This was a test to see the torsion and behavement of the rotorblades.

They sync'd the main rotorblades with he shutter from the camera. You have to synchronize it because the main rotor spins at different rpm for ascending and descendin.

[350z350zify]

@bumslug damn, your smart, im in algebra foundations in high school hah