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cangle49
08-08-2008, 02:35 AM
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