6 ms·

This is What Happens When You Run Water Through a 24hz Sine Wave

95 points by alexholehouse 14y ago

seanalltogether 14y ago
Do you have to do something special with the camera to turn off motion blur and simply take snapshots in order to achieve this effect?
- panic 14y ago
  Kind of. From the description in the YouTube video: Set up your camera and switch it to 24 fps. The higher the shutter speed the better the results. But also keep in the mind that the higher your shutter speed, the more light you need. Motion blur isn't something you "turn off" -- it's the natural effect of light being collected over time. The faster the shutter speed, the less time the camera spends collecting light each frame. That means both less motion blur and a darker image.
jared314 14y ago
Petapixel[0] has a better explanation. It is an illusion created by the synchronized frame rate and oscillation. They have used the same trick with a strobe light for live effects. [0] http://www.petapixel.com/2012/04/24/sound-and-frame-rates-used-to-make-water-travel-backwards/ http://www.petapixel.com/2012/04/24/sound-and-frame-rates-us...
- DanBC 14y ago
  YouTube has a bunch of videos showing strobe light version. Here are two short videos - the second one shows the effect nicely. (http://www.youtube.com/watch?v=OtxlQTmx1LE http://www.youtube.com/watch?v=OtxlQTmx1LE) (http://www.youtube.com/watch?v=ZRlNOyxWWf8 http://www.youtube.com/watch?v=ZRlNOyxWWf8)
alexholehouse 14y ago
I feel like there's some information theoretic approach which could be leveraged here, and maybe in similar systems - ie. just from the video we can work out - The difference in video frame rate vs sound frequency based on the period of the wave - Maybe the structure of the wave itself based on the waveform, although maybe not.
- darkarmani 14y ago
  Nyquist-Shannon: http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_samplin...
  - mvanveen 14y ago
    Wait, if I'm interpreting the Shannon-Nyquist theorem properly here, doesn't that mean since the signal is 24 Hz that we'd want a 48 FPS frame rate to accurately get the signal?
    - j-g-faustus 14y ago
      If you want to reproduce the signal, yes. But in this case they don't want that. They want the illusion that the water is standing still, which you get by sampling the signal at the exact same point in every cycle. So to the sampler/viewer it looks like there is no signal at all.
noonespecial 14y ago
"This is What Happens When You Run Water Through a 24hz Sine Wave" I'm not sure this is the best title. "What happens when you wiggle a hose at a frequency close to a camera's frame rate and then film the water coming out of it" might be better. At the most basic level, this is just the game you used to play with a hose when you were a kid by waving the end and producing ribbons of water in the air. The video just added a camera trick to photograph the ribbon in the same place during each oscillation appearing to freeze it in place. Initially I thought this was going to be much cooler, actually using the speaker to move the air through which the water was travelling to produce an effect. I was hoping for an awesome standing wave demo or something.
- JDGM 14y ago
  "The video just added a camera trick to photograph the ribbon in the same place during each oscillation appearing to freeze it in place." This is such a concise summary and I'm totally with you. I think. If I understand right, it would not be impressive to watch in real life and is just a property of the recording. Correct?
  - catshirt 14y ago
    unless you internally processed images at 24 frames per second, yes. however you'd be hard pressed to simulate this manually without any wave generator, which is why the speaker is crucial to the illusion.
    - zapdrive 14y ago
      I think normally we process 15-16 frames per second. So if I did this with a 16hz wave, would I see the same effect?
      - Dylan16807 14y ago
        Eyes don't work like that at all. They're continuous. You can fake motion with a low rate of pre-blurred frames, but parts of perception can get all the way up to hundreds of fps.
nostromo 14y ago
This blew my mind even more because the water looks completely frozen: http://www.youtube.com/watch?v=mODqQvlrgIQ http://www.youtube.com/watch?v=mODqQvlrgIQ I'm still amazed that the water comes out so uniformly.
justjimmy 14y ago
Oh come on, you can't show that video w/o filming what happens when you try to touch the stream! *The reverse flow is quite mind boggling :O
ChuckMcM 14y ago
A much more interesting effect is putting water and cornstarch on a woofer connected to an oscillator [1]. No special camera tricks required! [1] http://www.youtube.com/watch?v=3zoTKXXNQIU http://www.youtube.com/watch?v=3zoTKXXNQIU
- kbenson 14y ago
  It seems someone else was reading What If[1] today as well... [1]: http://what-if.xkcd.com/36/ http://what-if.xkcd.com/36/
tedsanders 14y ago
I bet this would work much better with glycerin or glycerin/water mixtures. Water has a low viscosity, meaning it's relatively easy to induce turbulence. And turbulence, while not exactly chaotic, is somewhat random and nonperiodic.
raghus 14y ago
Or this http://www.youtube.com/watch?v=mODqQvlrgIQ http://www.youtube.com/watch?v=mODqQvlrgIQ
helloamar 14y ago
Awesome example. Lot of information posted on this comment, that's why I love HN.

95 points by alexholehouse 14y ago

Do you have to do something special with the camera to turn off motion blur and simply take snapshots in order to achieve this effect?

panic 14y ago
Kind of. From the description in the YouTube video: Set up your camera and switch it to 24 fps. The higher the shutter speed the better the results. But also keep in the mind that the higher your shutter speed, the more light you need. Motion blur isn't something you "turn off" -- it's the natural effect of light being collected over time. The faster the shutter speed, the less time the camera spends collecting light each frame. That means both less motion blur and a darker image.

jared314 14y ago

Petapixel[0] has a better explanation. It is an illusion created by the synchronized frame rate and oscillation. They have used the same trick with a strobe light for live effects. [0] http://www.petapixel.com/2012/04/24/sound-and-frame-rates-used-to-make-water-travel-backwards/ http://www.petapixel.com/2012/04/24/sound-and-frame-rates-us...

DanBC 14y ago
YouTube has a bunch of videos showing strobe light version. Here are two short videos - the second one shows the effect nicely. (http://www.youtube.com/watch?v=OtxlQTmx1LE http://www.youtube.com/watch?v=OtxlQTmx1LE) (http://www.youtube.com/watch?v=ZRlNOyxWWf8 http://www.youtube.com/watch?v=ZRlNOyxWWf8)

alexholehouse 14y ago

I feel like there's some information theoretic approach which could be leveraged here, and maybe in similar systems - ie. just from the video we can work out - The difference in video frame rate vs sound frequency based on the period of the wave - Maybe the structure of the wave itself based on the waveform, although maybe not.

darkarmani 14y ago
Nyquist-Shannon: http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_samplin...
- mvanveen 14y ago
  Wait, if I'm interpreting the Shannon-Nyquist theorem properly here, doesn't that mean since the signal is 24 Hz that we'd want a 48 FPS frame rate to accurately get the signal?
  - j-g-faustus 14y ago
    If you want to reproduce the signal, yes. But in this case they don't want that. They want the illusion that the water is standing still, which you get by sampling the signal at the exact same point in every cycle. So to the sampler/viewer it looks like there is no signal at all.

noonespecial 14y ago

"This is What Happens When You Run Water Through a 24hz Sine Wave" I'm not sure this is the best title. "What happens when you wiggle a hose at a frequency close to a camera's frame rate and then film the water coming out of it" might be better. At the most basic level, this is just the game you used to play with a hose when you were a kid by waving the end and producing ribbons of water in the air. The video just added a camera trick to photograph the ribbon in the same place during each oscillation appearing to freeze it in place. Initially I thought this was going to be much cooler, actually using the speaker to move the air through which the water was travelling to produce an effect. I was hoping for an awesome standing wave demo or something.

JDGM 14y ago
"The video just added a camera trick to photograph the ribbon in the same place during each oscillation appearing to freeze it in place." This is such a concise summary and I'm totally with you. I think. If I understand right, it would not be impressive to watch in real life and is just a property of the recording. Correct?
- catshirt 14y ago
  unless you internally processed images at 24 frames per second, yes. however you'd be hard pressed to simulate this manually without any wave generator, which is why the speaker is crucial to the illusion.
  - zapdrive 14y ago
    I think normally we process 15-16 frames per second. So if I did this with a 16hz wave, would I see the same effect?
    - Dylan16807 14y ago
      Eyes don't work like that at all. They're continuous. You can fake motion with a low rate of pre-blurred frames, but parts of perception can get all the way up to hundreds of fps.

nostromo 14y ago

This blew my mind even more because the water looks completely frozen: http://www.youtube.com/watch?v=mODqQvlrgIQ http://www.youtube.com/watch?v=mODqQvlrgIQ I'm still amazed that the water comes out so uniformly.

justjimmy 14y ago

Oh come on, you can't show that video w/o filming what happens when you try to touch the stream! *The reverse flow is quite mind boggling :O

ChuckMcM 14y ago

A much more interesting effect is putting water and cornstarch on a woofer connected to an oscillator [1]. No special camera tricks required! [1] http://www.youtube.com/watch?v=3zoTKXXNQIU http://www.youtube.com/watch?v=3zoTKXXNQIU

kbenson 14y ago
It seems someone else was reading What If[1] today as well... [1]: http://what-if.xkcd.com/36/ http://what-if.xkcd.com/36/

tedsanders 14y ago

I bet this would work much better with glycerin or glycerin/water mixtures. Water has a low viscosity, meaning it's relatively easy to induce turbulence. And turbulence, while not exactly chaotic, is somewhat random and nonperiodic.

raghus 14y ago

Or this http://www.youtube.com/watch?v=mODqQvlrgIQ http://www.youtube.com/watch?v=mODqQvlrgIQ

helloamar 14y ago

Awesome example. Lot of information posted on this comment, that's why I love HN.