British Kinematography (1953)

46 BRITISH KINEMATOGRAPHY Vol. 23, No. 2 bin the Institution is giving consideration to the issue o\' a general memorandum on the subject of the measurement of frequency variation in sound recording and reproduction. In preparing this series of standards a careful review was made o\' the corresponding standards of the Society of Motion Picture and Television Engineers of America (Z22.60, 61, 65, 66, 67, 68), and there is a close measure of accord between the essential requirements in the British and the American standards. I he standards are intended to provide a basis for the uniform production of test films for use by projector manufacturers, users, and service engineers. They specify the essential requirements of the films but not the met hods of producing them, in order not to hamper technical progress in this field. Each part prescribes the sound characteristics of the sound track and its dimensions and location in relation to the guided edge of the film. When appropriate, information is given as to the lengths of film which can be obtained splice-free. Part 1 relates to a film for testing and adjusting the range and level of frequency response of the projector sound system at a projection speed of 24 frames per second. The series of test frequencies covers the range 60 to 8000 c.p.s. and is suitable for both laboratory and service use. Part 2 relates to a buzz track film for checking the position of the scanning beam. Part 3 relates to a film for use in balancing the respective power level outputs from two or more projectors. This film, if calibrated and supplied with a calibration record, may also be used to determine the overall sensitivity of the sound equipment. Part 4 relates to a film which may be used for the adjustment of the focus and aximuth of the soundoptical system in the projector. Part 5 relates to a film for determining the uniformity of the scanning beam in the sound-optical system in the projector. Two types of film are specified, one with a sound track suitable for use in laboratories and the other with a track suitable for use in the routine maintenance and servicing of the equipment. Test films should in all cases be regarded as prevision standards of reference, and since their careful storage is a matter of importance if their characteristics are to remain unaltered, each part gives detailed guidance on the manner of storing such films, which are required to be on a " safety " base. B.S. 2013 x 2014 : 1953 — 8mm. and 16mm. Projector Spools. Two comprehensive standards have recently been issued for projector spools for 8mm. and 16mm. cinematograph film (B.S. 2013 and 2014 respectively), and these two standards supersede the short schedules of dimensions which are included in B.S. 677, "'Motion picture film.*' The standard for 16mm. spools covers seven sizes o\' spools from 50 ft. to 2000 ft. capacity, and that for 8mm. spools covers four sizes from 50 ft. to 400 ft. capacity. The standards specify all of the essential dimensions, including the outside and core diameters, overall width and width between flanges, spindle mounting and drive, and accuracy of running. In the case of the larger 16mm. spools a maximum weight is specified in order that these spools when loaded and packaged may conveniently comply with postal regulations. In preparing these standards care has been taken to avoid any unnecessary restriction to the freedom of design, but such essential requirements are included as will ensure that the spools are well constructed and will give satisfactory service. They deal with such matters as the attachment of the flanges to the hub and the accuracy o\' assembly, the ribbing of the flanges, the >pindle clamping face, method of film attachment with its associated finger access holes, lightening holes and general finish. The material is not specified as it is intended that the specifications should apply both to metal spools and to spools of non-metallic materials such as plastics. 1 or 8mm. spools and 16mm. spools up to 400 ft. ;. . two alternative forms of spindle mounting are provided, namely reversible and non-reversible mounting, but in larger 16mm. spools the reversible mounting is the single standard method. In preparing the standard for 8mm. spools the most careful consideration was given to the practicability of issuing a single common standard for spools suitable for both 8mm. cinematograph film and for magnetic tape for sound recording. It ultimately appeared, however, that the requirements associated with magnetic tape recording were such that any common standard would increase the cost of spools for 8mm. film and it was finally agreed that it was preferable for each industry to have its individual standard. In preparing the standard for 16mm. spools the corresponding American Standard (PH22.11 — 1952) was reviewed. It may be noted that whilst there is a general accord between the British and American Standards, there are a few points of difference, in particular in respect of the outside and core diameters of the 800 ft. capacity spool which, in the British Standard, are smaller than the American. This latter point may require to be borne in mind by those who may be concerned with the export of 800 ft. spools, and film on 800 ft. spools, to America and certain of the Commonwealth countries. It may not be possible for spool manufacturers to meet all of the provisions of these new standards immediately, but it is hoped that their acceptance by the industry will encourage the general adoption of a limited number of types, thus facilitating economic production, will ensure absolute interchangeability and will remove any difficulties or irritations which may in the past have been associated with spools for small gauge films.