International projectionist (Jan-Dec 1956)

SCREENS, APERTURES AND ASPECT RATIOS [Continued from page 10) 1.65/1 ratio for regular, non-anamorphic prints gives rise to technical problems of film waste due to overly thick framelines, overworked projector intermittents, heating of the film by the arc lamp, and the number of frames per second needed to provide smooth, flicker-free projection at the highest light levels. As previously stated, the conventional 1.375/1 a.r. results in a waste, due to frameline thickness, of 15% of the total length of the film, while the 1.65/1 a.r. wastes fully 25%. The waste of film footage caused by the unused frameline areas is reduced in CinemaScope projection by the comparatively large apertures. CinemaScope framelines, being relatively thin, result in only 3.5% of unshown film length. The larger picture areas of CinemaScope films increase image definition and improve the focusing characteristics (depth of focus) of the projection lens. 3-Perforation Pulldown By employing an intermittent pulldown of 3, instead of the standard 4, perforations per frame of film, the resulting filmshift distance of 9/16 inch (0.5625") is enough to accommodate the 1.65/1 a.r. projector aperture (0.825" x 0.500") and permit the use of a necessarily larger camera, or printer, aperture (proposed dimensions: 0.87" x 0.55"). These dimensions result in an unused film-length in the camera of only 1.25%, and in the projector of only 6.25%. These figures compare favorably with the un used-length percentages in silent-film standardization, namely, 3% in the camera, 7.05% in the projector. Figure 5 is a side-by-side visual comparison of standard non-anamorphic release print and the proposed "3-hole" release print intended to be shown in aspect ratios of 1.65/1 and greater. Note that the 1.65/1 (or 1.66/1) a.r. projector aperture now in use for 4-hole film is to be used for 3-hole film. The picture area is NOT reduced by reducing the thickness of the framelines! A number of projection technologists have advocated the 3-hole frame shift for 35-mm film. There is nothing new in the proposal. It is worthy of serious consideration, however, first because of the necessity to restandardize the a.r. of normal-film projection, and secondly because the 3-hole pulldown offers several distinct advantages in addition to utilization of practically all of the picture area of the film. More Frames Per Second There are 16 frames per foot on standard 4-hole film. On 3-hole film there are 21% frames per foot, or 64 frames per 3 feet. If the present 24 frames per-second rate of exposure is kept, 3-hole film will travel only % as fast as 4-hole film, with a running time per reel 1% times that of present film. Instead of 1% feet per second (90 feet per minute), the travel rate of 4-hole film, the 24 frame/sec. 3hole film will run at the rate of 1% FIG. 5. Printing differences in 4-hole and 3hole frame placement. Note that the same 1.66/1 (or 1.65/1) a. r. wide-screen aperture is used with both kinds of projection print Higher aspect ratios may, of course, be used with the 3-hole frame shift. feet per second (67^/2 feet per minute). If, on the other hand, the linear running rate and showing time per reel is preserved in 3-hole film, the frame rate will be increased from 24 to 32 frames per second. The more rapid frame rate will result in a field rate on the screen of 64 exposures per second when regular 2-cutoff projector shutters are used. Projected pictures are virtually flickerless, regardless of light level, at 64 exposures per second. Yet another alternative exists, and one which is apt to be of greater interest to television engineers than to theatre-movie technologists. "If the frame rate of professional film is increased," argue the TV people, "it should be changed to 30 frames per second, the exact submultiple of the American TV field rate of 60 interlaced scannings per second." Let's see how the 30 frame/sec. rate affects running time and film consumption in the case of 3-hole film. It will change the travel rate from the present 1% ft. /sec. (90 ft./min.) to 1*1 ft./sec. (84% feet./min.). Therefore, 30 frame/sec. 3-hole film will run tb as fast as 24 frame/sec. 4-hole film, and the running time per reel will be 1-1/15 that of present film. The principal disadvantage of 3hole film standardization is the noninterchangeability with present-day 4hole CinemaScope prints. The anamorphic process could be readily adapted to 3-hole film, however; and by utilizing the whole 0.825" x 0.500" projector aperture and an anamorphic expansion factor of l1/*?, very high quality images in an aspect ratio of 2.475/1 would be obtained. (As an alternative, and with a slight sacrifice of picture quality and brightness, two 0.1-inch strips could be subtracted from the frame width for 3-channel stereophonic sound, leaving a projector aperture measuring 0.625" x 0.500", which, with an anamorphic expansion factor of 2, would result in a 2.5/1 a.r. picture.) Present Speed Favored Retention of the 24 frame/sec. rate is favored for 3-hole film prints. The advantages of this standard rate are fivefold. (1) Studio camera apparatus need not be altered. (2) Old pictures (Continued on page 34) 30 INTERNATIONAL PROJECTIONIST • JULY 1956