AP

DIRECT TELEVISION from ALEXANDRA PALACE

by Arthur Dungate

.

A Television Gallery

The 5x4 era

When 405-line television began in 1936 from Alexandra Palace, firstly as a demonstration to visitors to the annual Radiolympia Show in London in August, and then later as a regular service from November that year, the aspect ratio - or picture shape - was chosen as 5x4 (5 units wide by 4 units high). This made more efficient use of the available screen area of the round-faced cathode ray display tubes of the time.

Test patterns, on cards placed on easels, were used to line up the Emitron cameras in the studio, and similar patterns photographed on 35mm film were broadcast to allow adjustment of receivers.

Test
5x4 Test Card A
5x4
5x4 Tuning Signal
5x4
5x4 copyright notice
5x4
5x4 Tuning Signal
5x4
5x4 Tuning Signal

With the advent of World War II, the Television Service closed down at the beginning of September 1939. When it re-opened after the war, in June 1946 the same aspect ratio of 5x4 was used.

However the increasing use of cinema film, which had an aspect ratio of 4x3 - "Academy Ratio", made it desirable to change television's picture shape to match, and the change to 4x3 was made in April 1950.

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