How does a television show moving pictures?

Answer 1

The picture is made line by line, from the top left to the bottom right.

This makes up a frame.

The next frame is over written by a new frame, built up line by line.

The frames are drawn at 30 frames a second in the USA system and 25 frames in the UK and Europe.

If the picture has altered between each frame, this is seen as motion, by our eyes.

We do not see the frames separately, but a continuous motion the same as a movie picture. This is known as 'persistence of vision'.

In old Cathode ray tubes, this persistence was also enhanced by the phosphor coating, taking a while to fade, between scans of the Cathode ray.

Modern, flat screens using LCD, LED or plasma, do not have a natural fade, but can be delayed electronically to make the transition smooth.

Modern TV's, not relying on the actions of a cathode ray (or beam), can access each individual pixel on the screen. The picure is scanned into a short term memory and then transferred to the screen, in a simulation of the old scanning system. The frames can then be doubled up, to reduce any perceived flicker. The picture can also be paused, by just sending the same frame from memory, especially when the signal has been lost.