[News Engineer]

What is 25p out of curiosity? I’ve always wondered

Half the lines of the picture are drawn 50 times per second, so it’s 25 complete pictures per second. This is known as interlaced and technically described as 50i (or in some technical circles 25i).

Another way of making TV is to just capture 25 complete pictures per second - they’re still transmitted with half the lines each time. This is known as progressive, or in technical terms 25p. Or could be called a ‘filmic effect’ because it looks similar to the 24 frames per second of film. It’s what SVT have gone with tonight

It might sound like sending 50 half pictures per second or 25 complete ones wouldn’t be any different.

However, when using interlaced you capture some of the motion information each time half the lines on the screen are drawn. By only capturing 25 individual pictures per second about 1/3 of the motion is lost by comparison to 50 half pictures. And on a show like Eurovision it’s really obvious. It’s a creative decision to give the show a certain look and it’s very fashionable.

The good news is 4K broadcasts are 50 complete pictures per second. So better motion that interlaced pictures. Unfortunately it’s perfectly possible so shoot 25 pictures per second and send each twice.