True or false?

Discussion in 'Aviation Videos' started by Grampa, Dec 12, 2012.

  1. Grampa

    Grampa Member

    Joined:
    Feb 4, 2005
    Messages:
    542
    Likes Received:
    0
    Trophy Points:
    16
  2. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
    Staff Member Moderator

    Joined:
    Apr 9, 2005
    Messages:
    23,203
    Likes Received:
    786
    Trophy Points:
    113
    Gender:
    Male
    Occupation:
    Aircraft Maintenance Manager/ Flight Instructor
    Location:
    Colorado, USA
    The main rotor is really spinning, optical illusion from the camera
     
  3. meatloaf109

    meatloaf109 Well-Known Member

    Joined:
    Jan 1, 2012
    Messages:
    6,688
    Likes Received:
    252
    Trophy Points:
    83
    Occupation:
    plumbing "pro" at Lowes in Franklin N.C.
    Location:
    north carolina
    Either that, or photoshop.
    I believe very little of what I see on You-tube.
     
  4. Njaco

    Njaco The Pop-Tart Whisperer
    Staff Member Moderator

    Joined:
    Feb 19, 2007
    Messages:
    23,053
    Likes Received:
    994
    Trophy Points:
    113
    Occupation:
    Animal Control Officer
    Location:
    Southern New Jersey
    Agree with Joe.
     
  5. tyrodtom

    tyrodtom Well-Known Member

    Joined:
    Sep 6, 2010
    Messages:
    2,484
    Likes Received:
    110
    Trophy Points:
    63
    Occupation:
    auto body repair
    Location:
    pound va
    Haven't you noticed in films of aircraft shutting down their engines they appear to go slowly in one direction, stop, then go in the other direction. That's because the prop rpm is close to number of frames per second shot by the camera. That's how some crappy shows have the pictures of birds and insects that appear to have tandem wings.
    In that helicopter video the main rotor's rpm is sychronized with the video camera's frames per second.
     
  6. stona

    stona Well-Known Member

    Joined:
    Mar 28, 2009
    Messages:
    7,528
    Likes Received:
    947
    Trophy Points:
    113
    I thought that too but I can see a stationary shadow from a rotor blade a couple of times. I don't know whether that is part of the illusion.

    Steve
     
  7. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
    Staff Member Moderator

    Joined:
    Apr 9, 2005
    Messages:
    23,203
    Likes Received:
    786
    Trophy Points:
    113
    Gender:
    Male
    Occupation:
    Aircraft Maintenance Manager/ Flight Instructor
    Location:
    Colorado, USA
    Sums it up right there.........
     
  8. Capt. Vick

    Capt. Vick Well-Known Member

    Joined:
    Jul 23, 2008
    Messages:
    7,893
    Likes Received:
    637
    Trophy Points:
    113
    Gender:
    Male
    Location:
    Long Island, New York
    Which you would as a film is made up of a number of frames, with each frame capturing and instant of time. The shadow would be stationary (or appear to be) just as the blades are stationary (or appear to be). Obviously a shadow would exactly mimic the relative movement of whatever is casting it.
     
  9. N4521U

    N4521U Well-Known Member

    Joined:
    Nov 1, 2009
    Messages:
    8,633
    Likes Received:
    224
    Trophy Points:
    63
    Occupation:
    reduced to all around slobbing
    Location:
    Miranda, NSW
    Oh so true.........
    But, oh so cool.
     
  10. mikewint

    mikewint Well-Known Member

    Joined:
    Feb 17, 2010
    Messages:
    5,683
    Likes Received:
    430
    Trophy Points:
    83
    Gender:
    Male
    Occupation:
    Retired and living on the dole
    Location:
    Lakeview, AR
    stroboscopic effect. You can do the same thing at home using the TV. Spread your fingers apart and wave then back and forth in front of the screen or use a fan spinning in front of the screen. Wheels of a car speeding up or slowing down move forward, slow, stop, then reverse over and over
     
  11. tyrodtom

    tyrodtom Well-Known Member

    Joined:
    Sep 6, 2010
    Messages:
    2,484
    Likes Received:
    110
    Trophy Points:
    63
    Occupation:
    auto body repair
    Location:
    pound va
    I get the same effect when I use a timing light to set the spark timing on a car.
     
  12. A4K

    A4K Well-Known Member

    Joined:
    Dec 17, 2007
    Messages:
    12,162
    Likes Received:
    123
    Trophy Points:
    63
    Location:
    The back of beyond
    For same reason neon lights are forbidden in RNZAF workshops. A spinning lathe (etc) can appear stationary ...not good for the fingers.
     
  13. GrauGeist

    GrauGeist Well-Known Member

    Joined:
    Aug 29, 2008
    Messages:
    15,205
    Likes Received:
    2,041
    Trophy Points:
    113
    Occupation:
    Public Safety Automotive Technician
    Location:
    Redding, California
    Home Page:
    And sometimes, depending on the video camera, a propellor on an aircraft will appear as vertical bars if filmed from the cockpit...
    Also, I've taken many shots from the office of aircraft and the prop appears to be radiused depending on aperature shutter speed
     
  14. stona

    stona Well-Known Member

    Joined:
    Mar 28, 2009
    Messages:
    7,528
    Likes Received:
    947
    Trophy Points:
    113
    Good point :)

    Steve
     
  15. evangilder

    evangilder "Shooter"
    Staff Member Administrator

    Joined:
    Sep 17, 2004
    Messages:
    19,419
    Likes Received:
    137
    Trophy Points:
    63
    Occupation:
    Network Engineer/Photographer
    Location:
    Moorpark, CA
    Home Page:
    Yep, frame rate and spinning propellers cause some interesting effects. If you look at some of my flying videos, the props look like they are hardly spinning at all, or they get distorted. The normal video camera is 30 fps, makes it difficult to capture spinning objects.
     
  16. N4521U

    N4521U Well-Known Member

    Joined:
    Nov 1, 2009
    Messages:
    8,633
    Likes Received:
    224
    Trophy Points:
    63
    Occupation:
    reduced to all around slobbing
    Location:
    Miranda, NSW
    Been thinkin about this.

    My dream plane would be a Cessna 206C, STOL kit, tundra tires, gap seals.
    I could carry All the camping gear, And the beer!
    Any where I want!
     
  17. GrauGeist

    GrauGeist Well-Known Member

    Joined:
    Aug 29, 2008
    Messages:
    15,205
    Likes Received:
    2,041
    Trophy Points:
    113
    Occupation:
    Public Safety Automotive Technician
    Location:
    Redding, California
    Home Page:
    Here's a real quick example of what I was talking about, regarding the odd effects that a camera can produce when photographing objects like propellors, spoked wheels and the like...

    This shot was taken with a Pentax K100D DSLR camera during a flight in an Ercoupe several years ago, which has a two-bladed prop. The blades are definately straight and yet in this shot it's hard to tell if they're soft rubber or a new style shaped like a Scimitar (which would look badass, but highly impractical)...

    IMGP6090[720x479].jpg
     
  18. Airframes

    Airframes Benevolens Magister

    Joined:
    Aug 24, 2008
    Messages:
    47,691
    Likes Received:
    1,418
    Trophy Points:
    113
    Gender:
    Male
    Occupation:
    Retired
    Location:
    Cheshire, UK
    It's an effect more noticeable with electronic imaging (video/digital) than film cameras. A traditional cine camera normally shoots at 24 fps, compared to the 30 fps of a video camera, with each frame recording a separate, silver (photographic) image. A video camera is recording the equivalent of 30 FPS, but as an electronic 'signal'. The faster frame rate, and immediate 'capture', are similar to using a fast shutter speed, with a high ASA (ISO) film rating in a traditional 'still' film camera, where the faster the shutter speed, the more likelihood of 'freezing' a prop (or a spoked wheel, for example).
    You've probably noticed, in videos taken from the cockpit, that a prop might also seem erratic, turning fast, then slow, then stopping totally, then jerkily, and so on.
    In a traditional film cine camera, prop movement, depending on exposure conditions, is more likely to be shown as the human eye would normally see it, as a spinning disc.
     
  19. N4521U

    N4521U Well-Known Member

    Joined:
    Nov 1, 2009
    Messages:
    8,633
    Likes Received:
    224
    Trophy Points:
    63
    Occupation:
    reduced to all around slobbing
    Location:
    Miranda, NSW
    Personally I think the photo above proves the theory that as soon as a prop starts turning, it starts bending!
     
Loading...

Share This Page