Portal de Periódicos da CAPES

A 35-mm. Unit for Cinefluorography

1948; Radiological Society of North America; Volume: 51; Issue: 5 Linguagem: Inglês

10.1148/51.5.728

1527-1315

J S Watson, Sydney Weinberg,

History of Medical Practice

During the planning of the 35-mm. apparatus here described, the Department of Radiology was fortunate in having access to a 16-mm. unit assembled some ten years previously by engineers of the Eastman Kodak Co. under the supervision of Mr. Rex Willsey. Basically it consists of an f/0.81 cine lens of 4.1 cm. focal length made at the Eastman factory after a lens formula of B. Luboshez,2 and a Cine-Kodak Special camera with an unusually rapid pull-down or intermittent, which at normal camera speed moves the film into place in about one-fourth the time required by the conventional film shuttle. This Kodak experimental unit was designed primarily for ease and simplicity of operation. Recently the lens has been coated, and a Patterson B2 screen installed, increasing the photographic speed by more than 50 per cent. Probably no combination of this sort, using a refractor lens, requires less x-ray energy to expose the film. The new 35-mm. unit, while slightly inferior in photographic speed, embodies certain well tried technical refinements which it is hoped will give better pictures in some of the more difficult applications of cinefluorography. In spite of 16-mm. convenience and economy, 35-mm. film would appear to have a number of advantages in this field, not the least being that the larger film can be worked over on an optical printer without appreciable loss of quality. In this way the rate of action on the motion picture screen can be speeded up or slowed down. Many other changes can be made by optical printing, but slowing the action is perhaps the most useful, being nearly indispensable in the case of scenes which have had to be taken at less than normal camera speeds because of poor illumination. Optical printing of one sort or another has been in use since the earliest days of cineradiography, when serial radiograms were first rephotographed on cine film in an animation camera. In this kind of transfer each negative image is generally repeated a number of times on the print, even when the subject of the film is a slow-moving viscus (1). The process of positioning or registering unperforated negatives, however, is slow and laborious, and the resulting motion picture is not always as steady as one would wish. In the modern optical printer, on the other hand, where cine film is printed on cine film, the steadiness of the print is limited only by the accuracy of the film perforations. Due to the relative unsteadiness of the smaller film in this respect, 16-mm. to 16-mm. optical printing is not generally considered satisfactory, whereas 35-mm. to 35-mm. and 35-mm. to 16-mm. optical printing are highly perfected and available in most film centers. If the larger film is decided on, partly for reasons of steadiness, it would be inconsistent to employ any but the most reliable camera movement, preferably with register pins, even though the advantages of the quick pull-down would have to be abandoned.