International projectionist (Jan 1963-June 1965)

Focal length 1.913 x throw Throw picture width focal length x picture width 1.913 Picture width = 1.913 x throw focal length Aspect ratio = Width Height Height of Picture = Width Aspect ratio picture width based on a 2.21 to 1 aspect ratio. The above formulas and comparisons is in an additional small table to relate corresponding focal length in millimeters to dimensions in inches — just for general orientation. Even though the tables are self-explanatory, for the calculation of specific installations, with given lenses, screen sizes, and throw, the usual formulas can be applied using the dimensions of the 70mm aperture. The focal length lenses listed in the top column are all lenses especially designed to cover the 70mm aperture, and only such lenses should be used. Do not project 70mm prints with lenses only suited for 35mm apertures— even if they have a 4" O.D., and do not project 70mm prints by using supplementary lenses, lens attachments, or focal length converting devices. A 70mm projector alignment film with a test chart as shown in Figure 4 should be used to check lens performance for cleanest and sharpest picture projection. This test film is available through supply houses and shipped with instruction sheet for its use. It can also be ordered from SMPTE, 55 West 42nd Street. New York 36, N. Y. The Sound System The sound system for six-channel sound reproduction, as established for 70mm release prints, is generally handled by service organizations. We think, however, that it will be appreciated to publish the engineering facts on the six magnetic sound tracks on 70mm release film. As can be seen in Figure 2, the tracks are numbered from 1 to 6 — going from left to right if the film is placed with the magnetic coating up and the emulsion down. The tracks are used as follows: (with the listener facing the screen). Track 1 for the left speaker — Track 2 for the left center speaker — Track 3 for the center stage speaker — Track 4 for the right center speaker — Track 5 for the light speaker — Track 6 for the surround or auditorium speakers. The recording and reproducing speed is 24 frames (5 perforations) per second — representing exactly 120 perforations per second or 112.2 feet per minute. The center of the picture precedes the corresponding sound by a distance of 24 five-perforation frames. It should again be noted that the above specifications have been established by TODD-AO and are in accordance with their presently used process. In line with the specifications for 70mm composite film sound as outlined by the TODD-AO Corp., the theatre sound equipment should fulfill the following specifications: 1. The frequency response as measured on theatre equipment should be 50-8,000 cycles flat within plus or minus V2 db. 40-12,000 cycles flat within plus or minus 1.5 db. 2. Cross talk between channel . . . minus 40 db. at 1,000 cycles. 3. Signal to noise ... 55 db. 4. Wow and/or flutter not to exceed 0.2 of 1% in ^ band width between 2-200 cycles. 5. Preamplifier distortion not to exceed 1% when operated at a level of 12 db. above the level from magnetic film recorded at 3% distortion. 6. Power amplifier distortion not to exceed 2% at rated output of the amplifier between 50 and 12,000 cycles. 7. Speakers and power amplifiers should be of such power rating that any single track can properly fill the auditorium's acoustical needs. All necessary test films for checking 6-channel magnetic sound installations, as specified above, are available through the TODD-AO Corp., West Coast Division 1021 N. Seward St., Hollywood, Calif. IP 0.880 0.86O I ' 0.870 0.890 2.050 0.850 ♦ MOTION RESEARCH PICTURE COUNCIL HOLLYWOOD, CALIF. 1 imiiiii minim mini 111111111111111111111 iiiiii fc 1.710 750 1.900 L 1.920 1.940 2.020 m 2040 0.88O °-860 0 :♦ ♦ ♦ ♦ 111! = 2.030t 1.930 1.910-1 1.890 1.730 1.690 il !!!!!!! iiiiiiiiiiiHiiiiiumimmimimmmiiimT iiiiiiiiiiiiiiimiiiiimiiiiiiiiiiiiiiiiiiiiimiiiiiiiiMiiiiiiii mill !!!!!!!!!!!!!!!!!""""""" '"" """ humiiiiii llllllllllllllllllllllll IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIMIIIIIIIIMMII 70MM PROJECTOR ALIGNME NT FILM ♦ 1.710J 1.750 1 L L 1.900* 1.920J 1.940 111 2.020J 0-850 o.870 o.890 2.040^ J J 70MM TEST FILM CHART International Projectionist February, 1969