> From: Flamingfields@xxxxxxx
> Reply-To: "Basic and applied design (Art and
> Architecture)"<DESIGN-L@xxxxxxxxxxxxx>
> Date: Sat, 16 Feb 2002 08:06:44 -0500 (EST)
> To: DESIGN-L@xxxxxxxxxxxxx
> Subject: Re: seizures (old)// frame rates in US TV
>
> Patrick asked,
>
> I don't understand then the option between 30 and 60 frames per second.
> what for ?
>
> +++++++++++++++++++++++
>
> The "appearing" number of frames on NTSC television is 30 per second. The
> number 60 comes from the fact that an NTSC signal scans twice for each frame,
> projecting first one half of the frame data, then the other half. I am still
> trying to figure out whether this data is interleaved, or whether you get the
> top half, then the bottom half. I suspect the former.
>
> - Bascom Guffin
top half ? probably not. better interleaved. It would be a way to go to the
next start of the image in an elegant way.
but certainly more complexity then than in the pAL-secam system.
I always learned the scanning of the frame was in one direction, in Europe.
but actually it's also possible an ultrafast scanning must happen when the
beam goes back to the start of the next frame. It's supposedly then that
complementary info, eventually other data not relevant for the frame
fabrication is transmitted to the software of the receptor.
So then also you would have 25 frames per second, and another 25 other
ultrafast (and /or black - no visible signal) frames.
But if considering the "visible" frames, then, there would be only 25 images
- visible - per second in Europe.
But also as you wrote , then the NTSC would have 30 half frames downwards,
30 other half frames upwards, total only 30 complete IMAGES per sec. I
think we will agree...
but still wondering about the wasted material if copying 30 fps material
from video tape to a 24 fps on acetates. ( less differences from a 25 fps
video as in Europe)