4 ms·
Not quite! They capture one full frame every 1/30th of a second in the US and Japan, and 1/25th everywhere else. They capture one *field* every 1/50th of a sec
by Gordonjcp 4y ago
Not quite! They capture one full frame every 1/30th of a second in the US and Japan, and 1/25th everywhere else.
They capture one *field* every 1/50th of a second, and interlace it.
The reason for this is that it was hard to scan a full 625 lines in 1/50th of a second, and it would have required ludicrous bandwidth for the AM transmitters of the day and massive output valves to drive the scan coils in TV sets which would then produced huge flyback spikes.
So the decision was to scan 312.5 lines per field, offset slightly, with each pair of fields forming one 1/25th of a second frame. Telecine was easy in the UK because you could speed the film up a little and then each TV frame would be two fields per film frame.
If you shoot 50i you can deinterlace to 25p by combining the two sets of scan lines from each field with a bit of clever processing to hide the "combing" caused by things moving between fields, or you can double it up to 50p by just copying each line out twice with a bit of clever processing to smooth out the steps. I could post some video clips showing this if you were interested.
Of course modern digital TV cameras are capable of shooting 60p as you say, but anyone shooting "telenovela" stuff is going to be shooting 60i.
- warmcompress 4y agoThank you!! Our contemporary 60hz world seems to have retconned broadcast video standards.
- Gordonjcp 4y agoIt gets worse because for NTSC colour they changed it to 59.94Hz so that the colour subcarrier could be an odd multiple of the scan rate and just fit into the 4MHz-wide channels. This is why all your video editing software has got those ballachey 59.94/24.97 modes. It gets worse because for telecine you need to need to show two frames of 24fps film for every three frames of video, so you need to slow your film down to 23.976fps so it fits. Ballache.