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1945 Theatre Catalog, 4th Edition, Page 584 (556)

1945 Theatre Catalog, 4th Edition
1945 Theatre Catalog
1945 Theatre Catalog, 4th Edition, Page 584
Page 584

1945 Theatre Catalog, 4th Edition, Page 584

hibitors will welcome as a valuable contribution towards their theatre entertainment. The aim of the technician, who is primarily concerned with this aspect of television, will be to secure perfection independently in each of the divisions of work enumerated above. Outstanding among the problems are the following: (1) An increase in system definition, which will mean general progress under all sections; and (2) the improvement in theatre projection to a form comparable to the present film projection.

On the remaining problemsenamely, improvements in cameras, film scanning, cables, and radio linksemuch progress has been made, and the final necessary improvements will come in the course of solving the two major problems referred to above.

Equipment Used in Theatres

Taking as a basis equipment which has so far successfully been used, where definite lines of improvement can now

be visualized, development in the first instance will no doubt be concentrated toward obtaining a brighter and better picture with the high-voltage cathoderay-tube projection system which so far has formed the basis of the more recent demonstrations given by Baird, E. M. 1., and RCA. The first two have demonstrated high-voltage cathode-ray-tube projection with large aperture lenses; the last with an effectively large aperture mirror system. All three, however, have been projected from the center of the auditorium. The question of the positioning of the projection equipment is regarded as not of such great importance as the problems associated with the general improvement of the projected television picture.

Comparison with Cinema Standards 7

We must face the fact that television projection at the *moment compares unfavorably with normal film projection for the following reasons.

Brightness.-The maximum high-light

FIGURE 7.-Here is the Scaphony mechanical-optical receiver-proiector, installed in the Odeon Cinema, on London's leicester Square, in 1939. it was equipment of Scophony, Ltd., which was used in some early theatre demonstrations in the United States, and some of this original equipment is said to be still in use in Chicago. At the Odeon, as well as in other theatres where equipment was installed, special televised programs attracted sell-out audiences.



brightness so far achieved on the theatre large screen has been of the order of 1/2 foot lambert compared with 5 to 10 foot lamberts provided by black and white film projection.

DefinitioneSo far, nothing has been demonstrated having a definition represented by a standard of 525 lines, and it is doubtful if the best picture so far shown has had in practice a value of definition represented by a 300-line basis, on account of the many losses which are due to limitations in various parts of the system. If the equipment could reproduce the full detail associated with the perfect 525-line system, the picture would be good, but even then nothing like as good as the projected film which represents detail corresponding to something between a 1,000- and 2,000-1ine basis of scanning.

Quality of Picture.*The favorable reproduction of half tones in a full range of contrast has by no means yet been achieved. Many of the results bring to mind the soot and whitewash effect often associated with the early motion pictures; they show shadow effects which are disconcerting to the viewer, and the range of contrast between full black and full white is very limited.

Color.*TeleVisi0n has so far nothing to offer which can compete on the large screen basis with the color film.

Progress under these headings, particularly in respect of the first three, is of primary importance compared with problems of installation and operation.

Future Developments

The more important problems to be dealt with immediately are as follows.

(a) The determination of higher standard of definition necessary to provide the detail required, then having determined that to concentrate on the electrical equipment which will provide the synchronizing control and the amplifying and modulation needs for the requisite transmission channel. For example, supposing that it is agreed that approximater a 1,000-1ine basis will give all the detail that will be necessary, then a synchronizing generator system must be evolved, together with the video frequency and radio frequency systems that can handle modulation frequencies up to 20 megacycles a second. This factor determines also the requirements for distribution by cable and radio. Present coaxial cables, although very expensive to install, will satisfactorily handle frequencies only up to 2 or 3 megacycles a second. The extension for higher definition will increase the cost of these cables very considerably. The alternative is to use ultra-shortwave relay links which are limited in range. Thus We see quite a considerable program of work to establish in practice the higher definition standard and the distribution of pictures on such a basis.

(b) The problem of increasing brightness with existing systems of cathoderay-tube projection depends mainly on three things: (1) Increasing the brightness of the image in the cathode-raytube, and this in turn depends on being able to develop fluorescent materials

1945 Theatre Catalog, 4th Edition, Page 584