Journal of the Society of Motion Picture Engineers (1930-1949)

296 AMERICAN STANDARDS ON MOTION PICTURES Vol 46, No. 4 American Standard Specification for Multi-Frequency Test Film for Field Testing 1 6-Millimeter Sound Motion Picture Projection Equipment R^f. U. S. fat. Off. Z22.44-1946 1. Scope and Purpose 1.1 This standard describes a multi-frequency sound test film used for testing and adjusting the sound systems of 16-mm sound motion picture projection equipment. The test frequencies on this film are adequate for normal field and general laboratory use. 2. Test Film 2.1 Frequencies. The test film shall contain the following series of frequencies, each preceded by spoken announcement recorded at approximately 10 db below full modulation: Frequency Tone Footage Cycles Feet 400 50 100 200 300 500 1000 2000 3000 4000 5000 6000 7000 400 12 6 6 6 6 6 6 6 6 6 6 6 6 12 2.1.1 Frequency Tolerance. The frequency tolerance of the recorded signals shall be ± 2 percent of the nominal frequency of each portion of the test track. 2.2 Recording. The test film shall be an originally recorded, splice-free, direct playback, positive variable-area sound track, recorded so that the modulated light is substantially constant when the film is reproduced with a scanning beam of negligible width. Modulation of the recording shall be 95 =fc 5 percent at 7000 cycles. The level within any one frequency of each reel shall be constant to within ± 0.5 db. The recording shall be accomplished on a recorder so constructed as to keep the flutter content of the film to the absolute minimum consistent with the state of the art. The distortion of the recorded wave, up to a frequency of 3000 cycles, shall not exceed 5 percent. 2.3 Film Stock. The film stock used for the test film shall be cut and perforated in accordance with the American Standard 16Mm Sound Motion Picture Film; Cutting and Perforating Negative and Positive Raw Stock, Z22. 12-1 941, or latest revision thereof. 2.3.1 Resistance to Shrinkage. The film stock used for the test film shall have a maximum lengthwise shrinkage of 0.50 percent when tested as follows: At least 20 strips of film approximately 31 inches in length shall be cut for measurement of shrinkage. After normal development and drying (not over +80F [+26.7C]), the strips shall be placed at least V* inch apart in racks and kept for 7 days in an oven maintained at + 1 20 F (-f 49 C) and a relative humidity of 20 percent. The strips shall then be removed, reconditioned thoroughly to 50 percent relative humidity at +70F (+21.1 C), and the shrinkage measured by an adaptation of the pin-gage method outlined in Research Paper RP-1051 of the National Bureau of Standards. The percent shrinkage shall then be calculated on the basis of deviation from the nominal dimension for the length of 100 consecutive perforation intervals given in American Standard Z22.12-1941, or the latest revision thereof, referred to in 2.3 above. 2.4 Film Identification. Each test film shall be provided with a suitable leader, title, and trailer, and shall be accompanied by a calibration of the level of the frequency recordings. 2.4.1 Calibration. The calibration shall be in terms of light modulation at the photocell with a scanning beam of negligible width, and shall be correct to within =b }/4 db up to and including 3000 cycles, and within it Va db above 3000 cycles up to and including 7000 cycles. The correction for each frequency shall be so stated that it will give the true level when the correction is added algebraically to the output level measured using the film. NOTE: A test film in accordance with this standard is available from the Society of Motion Picture Engineers.