PAL basically has a subcarrier frequency of 4.3361875 mhz and a line
frequence of 15.625 khz which means the 2 waveforms are only in step once
every 2500 lines - 8 fields.
8 field lock only allows edits when fully coloured frames, but 1 frame in 4
is not as sony once put it in the sony 5000 manual 'not many editing
chances' so cutting on the 180 degree inverted point became common. Known
as 4 field lock or 'pal paired' this simply forces the picture to miove up
a scanline to be in phase. As these non pal edits only occur as cuts no one
notices and you match frame out for a dissolve equally out of phase so no
one is ever any the wiser.
It was never a problem with 2 inch but it became apparent in 1978 with the
introduction of 1 inch leading Roderick Snell to write his famous paper on
'springers and shifters' at the IBC conference that year... in that paper
he suggested component recording as a solution to colour framing issues.
On beta machines the 4 filed and 8 field lock was an attempt to conform to
pal video requirements from one inch sources and i think just worked off
timecode, there was also a colour frame flag that got set on the tape but
beta was the beginiing of the end for 8 field nonsense and D1 put paid to
it permanently.
best regards
Mike
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