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Bass String Motion Captured on Video

Discussion in 'Strings [DB]' started by Jazzdogg, Jan 4, 2012.


  1. Jazzdogg

    Jazzdogg Less barking, more wagging!

    Jul 29, 2006
    San Diego, CA
  2. CrazyZeke

    CrazyZeke

    Dec 29, 2009
    Eastern WV (DC suburbs)
    Endorsing Artist - Phil Jones Bass
    That video is proof positive of the need to have a properly set-up fingerboard! Great illustration of the string harmonics and just how complicated a note (tone) really is. A lot more than just the fundamental. Thanks for listing the video! :hyper:
     
  3. Michael Eisenman

    Michael Eisenman Supporting Member

    Jun 21, 2006
    Eugene, Oregon
    Gives new meaning to the phrase "noodling around".
     
  4. It's interesting to see how much the D string moves compared to the G and A.
     
  5. Loosebrace

    Loosebrace

    Jan 1, 2012
  6. SBassman

    SBassman

    Jun 8, 2003
    Northeast, US
    I'm dense, but - how are we seeing this if it's not slo mo?
    Somebody splain.
     
  7. Probably a very short exposure time (to avoid visual smear over exposure time) for every frame and maybe also a low frame rate.

    For those who are familiar with digital sampling theory:
    I think the slow motion is a visual aliasing effect (frame rate is the sampling frequency and higher frequency of moving objects is aliased), like the wheels of wagons in old western movies (slowly) running backwards when the wagon moves forward.

    Just a guess but I hope close to the truth.
     
  8. This has been discussed in another thread in the past (about the same clip, funnily enough). I don't think that the strings are actually doing that; I think it's a strobing effect/interference pattern caused by the refresh rate of the camera system interacting with the strings' frequencies. The effect varies from string to string as the different frequencies interact numerically (ie, in/out of phase, qtr, half, full etc wavelengths) with the scan rate. This also explains why we can see the effect at 'normal' speed (as opposed to slow motion).

    You can duplicate the effect by looking through your vibrating strings at the picture on a cathode ray tube (CRT) TV (I haven't tried it with an LCD or plasma); our Australian PAL standard refreshes at 50Hz, so the effect worked for me around multiples of that.
     
  9. hdiddy

    hdiddy Official Forum Flunkee Supporting Member

    Mar 16, 2004
    Richmond, CA
    Yeah, it's just camera frame rate vs string frequency. It's the same effect you see when you watch a wheel spokes, or a propeller on a helicopter/airplane make the optical illusion that it's spinning backwards.

    Some of those shots are slowed down a little bit but they were shot at higher frame rates (like 30 frames per second or more) so it looks very smooth when you play it back at a slower rate. Camera trickery that is getting more and more common these days...
     
  10. It's actually camera LINE rate not camera FRAME rate; that was shot with a rolling-shutter camera, which means that the exposure is taken progressively from top to bottom, not simultaneously for the whole frame.

    Which looks cool, but doesn't tell you the shape of the string at any given moment. What it does show you, though, is how far it travels.
     
  11. +1 Andrew; similar reason to how it works on the CRT (the electron gun draws the picture as horizontal lines from the top of the screen downwards & starts again when it reaches the bottom. The frequency per second at which it achieves this is the vertical scan/refresh rate).
     

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