By J. H. BAIRD
Baird Television, Ltd.
from the American Cinematographer Magazine, February 1942
WHEN war broke out, television in England was firmly established and appeared to be entering upon a period of prosperity long delayed. Preparations were in hand to meet a large and rapidly growing demand for televisors both for the home and the cinema. With the outbreak of war the television transmission service was immediately stopped, and the results to the growing industry were catastrophic. With no transmissions available receiving
sets were useless and commercial television came to an abrupt standstill.
The company of which I was President (Paird Television, Ltd.) one of the worst sufferers, was unable to continue. At that period I was engaged on research in Color Television, work which I have continued in private during the war. The transmission of television in color is not new: it was shown for the first time in public as far back as 1028, when I gave a demonstration at the annual meeting of the British Association. The demonstration was entirely experimental but the principle then shown is the same as that used in the latest apparatus.
It is in fact a process similar to color printing, three images corresponding to the three primary colors (red. green and blue) being superimposed. In the first color television apparatus, the three colored images were obtained from a disc perforated -with three spirals of holes, one spiral being covered with a red filter, the other with a green, the third with a blue; and the three pictures so produced were superimposed to form an image in natural colors.
The picture then shown was very small, only a few inches square and of poor quality. Development since that date has been slow, since general attention has been largely centered on monochrome. At last in 1938 I was able to
show a 12 ft. by 9 ft. Color Television picture transmitted by wireless from the Crystal Palace to an audience of 3,000 in the Dominion Theatre. The apparatus used, however, was costly and complex and not practicable for the home.
Immediately before the outbreak of war, in August, 1939, I was able to show Color Television for the home by using a rotating disc fitted with color filters in front of the ordinary Cathoderay tube of the present-day home receiver. In our latest apparatus the number of lines has been increased to 600, giving nearly twice the amount of detail available on the British Broadcasting Company’s black-and-white pictures. Both three-color and two-color processes have been experimented with. For practical purposes the two-color has much to recommend it at present and in our latest apparatus a two-color process is used in conjunction with a special form of scanning, a triple-interlaced 200-line primary field being employed, alternate fields passing through red and blue filters giving a final 600 line picture in color.
The complete field is scanned 16 2/3 times per second and complete colored pictures are transmitted at the rate of eight and one-third per second. With triple interlacing and alternate primary scans colored, this very low picture frequency can be used without undue flicker and with the very great advantage that the 600-line color picture can be transmitted on the same wave-band as that used by the B.B.C. for their 405-line black-and-white transmission.
The use of two colors in place of three simply means substituting a twocolor disc for a three-color. It entails a loss in color rendering, but if three colors are used a much wider channel is necessary for transmission, and considerable alterations in existing apparatus are required.
We are experimenting with both three and two-color, but for practical working the use of two colors has many advantages and commercial color television will probably commence with a two-color system which is immediately adaptable to existing apparatus and available channels.
After the war the broadcasting of color television will, I feel sure, be one of the major television developments. The colored television picture is far superior to the monochrome, and sooner or later must supersede it. As far as
Britain is concerned, the television service will be extended to cover the whole country instead of being confined to the London area. Cinemas will be equipped with television screens and television will become a regular feature of their programmes.
The importance of the television service is well recognized to-day and we may look forward to its early resumption as one of the first post-war developments.