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1080/50/I and 1080/25PSF...what's the difference?

04-20-2005, 11:53 AM
Can someone please explain this to me?

I have a 1080/25/P feature film (film and produced all in progressive) and I want to make a version to play in England but don't have the bandwidth to transmit that format so say my two options say are to produce:
1080/50/I (1080 lines, 50 fields, interlaced)
1080/25PSF (1080 lines, 25 progressive segmented frames)

when I convert from 25p to the interlaced system I am splitting that frame into two producing 2 fields, each field has the same image (the image does not change between field 1 and field 2), each containing 540 lines, the first field scans the odd numbered lines and the second field scans the even numbered lines etc, what happens when I want to make a 25PFS from the 25p master, surely it takes exactly the same route as the 50/I system does? or are the segmented frames scanned differently?

If they are identical what is the point in have 2 systems that are the same?