Archived from groups: rec.video.desktop (
More info?)
"leo" <someone@somewhere.net> wrote in message
news:tQxhc.5339$e4.4511@newsread2.news.pas.earthlink.net...
> "Richard Cavell" <richardcavell@hotmail.com> wrote in message
> news:4085b4f6$0$27642$61ce578d@news.syd.swiftdsl.com.au...
> > Maybe I'm just tired, but can someone explain this, from the NBC
website:
> >
> >
http://www.nbc.com/nbc/footer/HDTV.shtml
> > For those of you are really technically inclined, think about this:
movies
> > and many primetime shows that are produced on film are made with only 24
> > pictures per second, so 1080i actually becomes progressive scan when
> > film-based material is being broadcast!
>
>
> 1080i is good enough for movie but 24fps is not satisfactory for fast
> motions. That really requires at least 60fps.
>
That is one of the Video/film differences. Video used to be very much
real-time. That is to say that the electron beam in the camera was scanning
the target in the tube in full sync with the TV at home. The exposure time
at any point on the screen is the amount of time it takes to scan the beam
over that point. Of course there are minor propagation delays, but other
than that, TV was really "live". A lot of the opinions in the video/film
question
date back to that time. Now cameras have chips and that changes everything.
Fields (or frames in a camera equipped for progressive) are captured all at
once,
much as film frames are captured. The exposure time can be as long as the
time between frames (or even longer by overlapping the frames). By making
the
exposure longer it is now possible to use "motion blur" to smooth the
motion.
This is how film folks get away with such a low frame rate. But that only
goes
so far. Cinematographers must learn some tricks to help them cope with
action.
The stuttering can be reduced in several ways.
Motion blur is one. Another is having the motion moving towards or away
from the camera (the effect is reduced by limiting the lateral motion). You
can
also track the fast moving object to keep it relatively stable in the frame,
and
then blur out the background so it just becomes a fast moving smear. The
same tricks can be used in video, but most people don't bother. The
interlace
artifacts that people are always complaining about can be greatly reduced
by good film-like camera work.
Some say that his limitation of film is a big part of what makes film better
than video. I say it is a small part. If you shoot video the way film is
shot,
it will look more like a feature film than shooting video the way video is
shot.
David
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