On Fri, 10 Mar 2000, Benno Senoner wrote:
> > >Why? The human eye has a lower sampling rate. 30 Hz should really be
> > >enough.
> >
> > Thanks, I didn't know that.
>
> Little correction:
> for example: PAL TV uses 25 FPS , NTSC TV uses 30 FPS,
> cinema movies use 24 FPS.
>
> Although 24-30 FSP is enough to provide a fluid movie,
> the movie is not as as smooth as you think.
>
> During very fast movements you can see the "comet" effect a little
> (you see the borders of the fast moving object a bit overlapped with the
> borders of the object in last frame).
This is due to the interlace of the NTSC and PAL systems. PAL uses
two frames, with a frame rate of 50 Hz. Every other frame is offset
by half a raster line distance. The comet effect is due to the
differences between half-frames being visible.
The same effect does occur on interlaced computer displays as well,
but most are non-interlaced these days.
BTW, the reason why you don't see this effect on computers that
generate PAL/NTCS output directly (C64, Spectrum, Amiga, ST,...)
or on game consoles in their low resolution modes, is that they fool
the TV set/monitor into using the first half-frame for every frame,
ie 50/60 full frames (with half the vertical resolution) per second.
> Therefore since peak meters move quite fast , I'd suggest to use 40-50 Hz
> for maximum fluidity. more that 50Hz doesn't make any pratical sense.
Well, I don't know if it makes much difference unless the meters are
*BIG*, but there is only one correct frame rate for smooth animation:
the *exact* rate of the display. Raster sync is required, just as for
video games.
//David
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