PICTURES BY RADIO

New Zealand Times, Volume LIII, Issue 12618, 1 December 1926, Page 8

PICTURES BY RADIO

DEMPSEY-TUNNEY FIGHT WONDERFUL RINGSIDE PHOTOGRAPH FLASHED TO LONDON IN AN HOUR The picture of the Dempsey-'funney fight which we publish in this issue, although not the first photograph to be sent by wireless, is probably the most amazing and realistio ever sent to a newspaper office. It shows the absolute helplessness of Dempsey against the terrific right of his conqueror, Tunney. and the contrast which Dempsey presented in the ring as against the dominating attitude he exhibited in previous contests. Here we see the sledge-hammer blow which seems to have paralysed the one-time invincible champion. Judging by Tunney’s atti-

tude, the blow must have descended like a thunderbolt. The wonder is that Dempsey was not knocked out instantly. WONDERFUL WORK The photograph, which was dispatched by “World’s News” (London) special representative at ttie ringside, took exactly one hour in transmission, and it may interest readers to know that the actual cost was £23 10s. The transmission took place from the Central Radio Office, Broad-street, New York, the picture being received at the Marconi headquarters in London end delivered to the paper. Its faithfulness of detail, considering the difficulties .that beset the photographer, working at the ring-side, demonstrates the pitch of perfection attained in the apparatus used for sending pictures by radio.The delicate machine used to transmit the illustration across the Atlantic looks bafflingly complex to the uninitiated eye, yet its principle of working is simnle. . Actually, the photograph speeds across the ocean wastes in the form of a rapid series of elec-

trical signals, like dots in tile Morse code, of varying intensity. These are, of course, utterly meaningless to all except those possessing the apparatus required to construct them into proper form. The transmission is made from a positive print in the form of a piece of photographic film. This is attached to a cylinder composed of glass. Inside the cylinder, which rotates backwards and forwards, a tinv spot of intensely brilliant light is directed LIKE THE POINT OF A PENCIL on to the film. Beginning at one corner this minute light, by the movement of the cylinder travels backwards and forwards, gradually traversing the whole surface in a series of close parallel lines. The light, passing thro.-vn the film, falls in varying intensitv, due to the different shades of the photograph, on to a photo-electric cell. This, for all practical purposes, works in.the fashion of a human eye. Under the influence of strong light it closes up, and under subdued rays it opens. The internal resistance of the cell varies with the amount of light that reaches it through the film, and this variation in the current it gives off acts on an amplifier, which finally operates a telegraphio transmitter. The

transmitter then sends out the dot signals forming the picture. INTO PICTORIAL FORM The receiving apparatus in London re-translates these signals into pictorial form in the following way: The dot impulses are amplified and made to work a recording mechanism, to which is attached a stylus, or pen, that traverses a roll of paper. The movement of this p;)per synchronises perfectly with that of the film on the glass cylinder of the sending station. The density of the positive film is registered in faithful detail by the stylus which crosses the paper roll in a series of dotted lines, varying from almost perfectly white to deep black. As iastrument ticks out its “message” the operator standing by is able to see the transmitted picture being built up line by line, beneath his gaze, o-n the recording paper. When completed he removes the print from the machine and delivers it to its destination, just like an ordinarv post-office telegram. Many copies of the transmitted il l ’* tration can, of course, he taken by the process of re-photographing.