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  • Pulldown

    Does anybody have any advice on pull down. Some of the new camcorders
    have pull down rates (see definitions below from websites). Can I assume
    that if I purchase a new camera and don't film in cinematic mode (read
    below) and the camera says it is capturing at 29.97 fps, that my
    velocity data is reliable? Normally we use more scientific cameras but
    with an up coming project we have to purchase 10 simple to use cameras
    on a 3000 dollar budget. So I am not familiar with the reliability of
    the low end everyday camcorder (JVC GR250, Cannon ZR830, and Panasonic
    PV GS59).

    When in the Cinematic Effect mode, the Sony camcorder brings video in at
    30 progressive frames per second. To get the film-like effects, the Sony
    DCR-PC350 drops every fifth frame. The camcorder then uses what’s called
    a 2:3:3:2 pull down to convert the now-24p video into a signal that can
    be recorded onto a normal Mini DV tape. The Panasonic AG-DVX100 uses the
    same 2:3:3:2 pull down; however, the Panasonic is working with true 24p
    video, whereas the Sony is using 30 frames-per-second video with every
    fifth frame thrown out.

    *Other definitions of pull down:
    Pulldown *­ introducing a pulldown is the process which compensates for
    the differences in frame rates between film and video by creating new
    frames. For 24 fps film to be converted to 30 fps NTSC video, a 3/2
    pulldown is used which creates an extra 6 frames per second.

    *3:2 Pulldown* The technique used to convert 24 frames per second film
    to 30 frames per second video. Every other film frame is held for 3
    video fields, resulting in a sequence of 3 fields, 2 fields, 3 fields, 2
    fields, etc.

    *3:2 Pulldown* – Movies are filmed at twenty-four frames per second
    (fps). Televisions operate at thirty frames per second. If we simply
    show the movie at 30fps it will appear to go too fast – the "Keystone
    Cop” effect. The “3:2 pulldown,” method repeats selected movie frames a
    second time to display the 24fps movie on the 30fps television at the
    right speed

    Thanks,


    --
    Craig Angle M.Ed, M.Ed, ATC, CSCS
    Research Associate II
    Veterinary Sports Medicine Program (www.vetmed.auburn.edu/sportsmed)
    Auburn University, College of Veterinary Medicine
    Doctoral Candidate, Biomechanics Program
    Department of Kinesiology, Auburn University
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