60i, 30p, 29.97, 24p, 23.976 WHAT?!?!?
- Thread starter iFilm7
- Start date
BobDiaz
The Professor
BACKGROUND:
In the early days of Black & White TV in the USA, the vertical frequency was exactly 60 Hz.
The introduction of color to TV created a problem with a frequency of 60 Hz. The color sub-carrier frequency would generate a beat pattern with the sound sub-carrier frequency. One of the frequencies had to be changed.
(1) Change the color sub-carrier: by lowering all the scan frequencies by 1000/1001 (0.999), 60 Hz became 59.94 Hz and there was not a problem with any beat pattern.
(2) Increase the sound sub-carrier frequency by about 5 kHz. While this would work, all the TVs out there would be slightly off on the sound frequency adjustment.
Sadly, time code didn't exist at that time, so solution #1 was chosen.
It's common for us to talk about 60p, 60i, 30p, and 24p, BUT in reality all the numbers are slightly off from reality: 60p x 0.999 = 59.94p, 60i x 0.999 = 59.94i, 30p x 0.999 = 29.97p, 24p x 0.999 = 23.98p.
However, I find it a lot easier just to say, 24p, rather than 23.98p. So even if 60p, 30p, and 24p isn't exact, it's easier to express.
Bob Diaz
In the early days of Black & White TV in the USA, the vertical frequency was exactly 60 Hz.
The introduction of color to TV created a problem with a frequency of 60 Hz. The color sub-carrier frequency would generate a beat pattern with the sound sub-carrier frequency. One of the frequencies had to be changed.
(1) Change the color sub-carrier: by lowering all the scan frequencies by 1000/1001 (0.999), 60 Hz became 59.94 Hz and there was not a problem with any beat pattern.
(2) Increase the sound sub-carrier frequency by about 5 kHz. While this would work, all the TVs out there would be slightly off on the sound frequency adjustment.
Sadly, time code didn't exist at that time, so solution #1 was chosen.
It's common for us to talk about 60p, 60i, 30p, and 24p, BUT in reality all the numbers are slightly off from reality: 60p x 0.999 = 59.94p, 60i x 0.999 = 59.94i, 30p x 0.999 = 29.97p, 24p x 0.999 = 23.98p.
However, I find it a lot easier just to say, 24p, rather than 23.98p. So even if 60p, 30p, and 24p isn't exact, it's easier to express.
Bob Diaz
Barry_Green
Moderator
Yes, you'd do that with footage from any video camera.