Film ID:
YFA 2947

COLOUR TV TRANSMISSION

1960s

Visitor Tabs

Description

This is an educational film that uses diagrams to explain how colour and black and white TV is filmed, transmitted, received, and displayed on a television.

The film begins showing how colour pictures can be transmitted from the studio. A diagram shows the inside of a camera and how light is divided into the three primary colours. Two mirrors divide the light into three tubes, separating out red, blue, and green light rays. The light is transformed into a pattern of electrical charges and scanned producing an endless signal of electrical impulses. These are conveyed to a picture tube. Each of the three signals activates a corresponding photosphere. In the screen, the colours are combined to reproduce the original image.

Signals can also be conveyed by cable for close circuit television. For black and white images, radio signals are sent using just one signal through a transmitter which sends an electro-magnetic wave. Colour images are sent in the same manner making the two systems compatible. With colour images, the three primary colours are combined in a circuit to produce the luminal signal. A sign wave oscillator transforms this into a modulated sub-carrier signal. Both colour and black and white signals are modulated on the same electro-magnetic wave. Circuits at the receiving end reconstitute the colours.

The colour tube is explained by showing three guns for each colour. The light strikes luminescent dots of the three primary colours. A perforated mask prevents the colours from striking the wrong dots which are placed so that the right ones are hit due to the different angles of the colour beams. The constant rhythm of the light produces the effect of a constantly radiating screen. The different amplitudes of the coloured lights causes variation in brilliance producing colour television. The camera zooms out on the image to reveal coloured balloons on a TV screen. The film ends with the logo for Mullard.