🚀 go-pugleaf

In article <1992Aug14.121823.27891@bcrka451.bnr.ca> sandness@bnr.ca (Glen Sandness) writes:
>
>Several CCD image sensors I have read about generate the interleaved
>NTSC signal by simply dumping the same 200+ scan lines for each field
>of a complete frame.  This means that the second field of the frame
>is actually offset in time from the first field.  Is this how all
>video cameras operate?

Most pro video I've seen seems to shoot 60 distinct fields per second,
where if you do a frame still you may get motion artifacts due to the
fields being taken from different points in time.

I don't know about consumer cameras.

>I know that motion picture film is converted to video by periodically
>re-using frames to reconcile the 24-frame/sec motion picture rate with
>the 30-frame/sec video rate.  Does that mean that in this case the
>second field of the frame is NOT offset in time from the first field
>(i.e. both fields have been recorded from the same static movie frame)?

The method normally used is "3-2 pulldown" in which half of the film
frames use 2 fields and the other half use 3 fields, in an alternating
fashion:

video frame  |1    |2    |3    |4    |5    |
video fields |  :  |  :  |  :  |  :  |  :  |
film frame   |1 :1 |1 :2 |2 :3 |3 :3 |4 :4 |

So 2 out of 5 video frames have fields taken from different film
frames.

                                              -Dave Dodge/dododge@wam.umd.edu