1、BRITISH STANDARD BS 5550-1.3.3: 1980 Incorporating Amendment No. 1 Cinematography Part 1: 8 mm film Section 1.3 Camera usage Subsection 1.3.3 Specification for claw-to-gate distance in 8 mm Type R spool-loading cinematograph equipmentBS5550-1.3.3:1980 This British Standard, having been approved by t
2、he Cinematography Standards Committee and endorsed by theChairman of the EngineeringDivisional Council, was published under the authorityof the General Councilon 1 June 1964 as BS 3747 BSI 02-2000 The following BSI references relate to the work on this standard: Committee reference CMS/28 Draft for
3、comment D62/6224 ISBN 0 580 03897 1 Co-operating organizations The Cinematography Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Board of Trade British
4、 Broadcasting Corporation British Film Institute British Film Producers Association British Kinematograph Society* Cinematography Exhibitors Association of Great Britain and Ireland Federation of British Film Makers Federation of Specialised Film Association Home Office Illuminating Engineering Soci
5、ety Incorporated Association of Kinematograph Manufacturers Ltd.* Independent Television Companies Associations* Kinematograph Renters Society Ltd. Royal Photographic Society* War Office The scientific and industrial organizations marked with an asterisk in the above list, together with the followin
6、g, were directly represented on the committee entrusted with the preparation of this British Standard: Association for Science Education British Amateur Cinematographers Central Council British Photographic Manufacturers Association British Universities Film Council Educational Foundation for Visual
7、 Aids Federation of Film Societies Film Laboratory Association Institute of Amateur Cinematographers Institute of British Photographers Ministry of Education National Committee for Visual Aids in Education Photographic Dealers Association Scientific Film Association Manufacturers of 8 mm cinematogra
8、ph equipment Amendments issued since publication Amd. No. Date of issue Comments 2831 September 1980 Indicated by a sideline in the marginBS5550-1.3.3:1980 BSI 02-2000 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Claw-to-gate distance 1 Appendix 4 Figure 1 Po
9、sition of claw 1 Figure 2 Effect of claw-to-gate distance with film having irregular perforation pitch error 2BS5550-1.3.3:1980 ii BSI 02-2000 Foreword This British Standard has been prepared under the authority of the Cinematograph Standards Committee in response to a request submitted by the Briti
10、sh Kinematograph Society. The standard is intended for application in new designs of equipment. From such information as has been collected on the current practice of camera and projector manufacturers it is believed that the value adopted for this British Standard is that most widely adopted throug
11、hout the world. The reasons underlying the importance of uniformity in the claw-to-gate distance in all makes of equipment are given in the Appendix. This British Standard (as BS3747) was confirmed in1977. All British Standards on cinematography are eventually to become Sections or Subsections of BS
12、5550. Accordingly this British Standard has been renumbered as BS5550-1.3.3. BSI Sectional List1, obtainable free from BSI Sales Department, catalogues the British Standards on cinematography. The latest edition of SL1should be referred to in view of these developments. A British Standard does not p
13、urport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside fron
14、t cover, pages i and ii, pages1 to 5 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS5550-1.3.3:1980 BSI 02-2000 1 1 Scope This British Standard specifies the reg
15、istering perforation with respect to the image on8mm TypeR motion picture film, and is applicable to spool-loading cameras, projectors and step-printers. NOTEIn the design of magazine loading cameras and projectors, the specified distance between claw and gate may not always be capable of realizatio
16、n. It nevertheless represents the desirable practice which should be followed when design considerations permit. 2 Claw-to-gate distance The operating claw in8mm cameras, projectors and step-printers, at the completion of the pull-down stroke shall be at a position which is two frames beyond the pic
17、ture aperture in the direction of film travel (not including the frame which is in the aperture at this moment) as illustrated inFigure 1. In equipment using multi-tooth claws, this position shall relate to that of the operative tooth of the claw. Figure 1 Position of clawBS5550-1.3.3:1980 2 BSI 02-
18、2000 Figure 2a Uniform perforation of film Figure 2b Irregular pitch error in film Figure 2c Film 2b being exposed in a camera The position of the claw is at the end of the pull-down stroke. Figure 2 Effect of claw-to-gate distance with film having irregular perforation pitch errorBS5550-1.3.3:1980
19、BSI 02-2000 3 Figure 2d Processed film 2b after exposure in camera 2c Figure 2e Processed film 2d being projected with a claw displacement different to that of the camera Figure 2f Processed film 2d being projected with a claw displacement the same as that of the camera The position of the claw is a
20、t the end of the pull-down stroke. Figure 2 Effect of claw-to-gate distance with film having irregular perforation pitch errorBS5550-1.3.3:1980 4 BSI 02-2000 Appendix The vertical steadiness of a projected picture is directly dependent upon the uniformity of the advancement of the film from frame to
21、 frame in camera, printer and projector. The perforation of the film, although reaching a high degree of accuracy in modern manufacturing processes, cannot however be absolutely precise and it must be recognized that there are slight deviations in pitch from one perforation to the next. These deviat
22、ions are, of course, very small, and in the case of35mm and16mm films do not normally result in any disturbing unsteadiness in the projected picture. Manufacturing processes are such that it is not at present practicable to reduce the dimensional amount of tolerance in pitch for the narrower gauges
23、of film. Thus the tolerance in relation to the actual image size is twice as great in8mm film as in16mm film, and four times as great as in35mm film. Every means possible have therefore to be taken to minimize the effects of pitch error in the case of8mm film if the steadiness of the projected pictu
24、re is to be acceptable. Figure 2a illustrates a film with theoretically uniform perforation, andFigure 2b illustrates a film with irregular pitch error (greatly exaggerated in the diagram). In designing cameras, projectors and step printers it is generally found convenient to locate the operating cl
25、aw at some little distance from the aperture in the gate. In the past there has been no universally accepted displacement and cameras and projectors are to be found in which the displacement may vary as much as from minus four frames (the claw being behind the picture aperture, expressed in relation
26、 to the direction of travel of the film) to plus six frames (the claw being ahead of the picture aperture). The unexposed film in the camera has no “frame”, only perforations. Each frame is generated as it is exposed. It will thus be seen that the position of the generated frame is related to the po
27、sition of the claw at the end of its pull-down stroke. Figure 2c illustrates the condition when the operating claw at the end of its stroke is in the third perforation below the centre line of the aperture. If there is irregular pitch error in the film (as inFigure 2b) there will be a corresponding
28、varying pitch in the exposed frames and the developed film will appear as inFigure 2d. Suppose that this film is a reversal film and is now projected. The position of the film in the gate at the end of each pull down is related to that perforation which has been operated by the claw in the projector
29、. The images on this film (because the film has pitch error in the perforations) are not however uniformly spaced. Suppose that the projector is one in which the claw operates in the perforation which at the end of the stroke is the second perforation below the centre line of the projector aperture.
30、 The projector is now showing the particular image taken by a camera corresponding toFigure 2c, but because the projector claw is operating in a different perforation from the perforation operated by the camera claw when taking this particular image, and because there is a pitch error between these
31、two perforations, the image will not be in its correct position in the aperture but will appear as in Figure 2e. A succession of such pictures, in varying positions in the aperture, produces picture unsteadiness. If, however, the projector is one in which the claw operates in the perforation which a
32、t the end of the stroke is the third perforation below the centre line of the projector aperture, that is to say the same perforation as was operated by the camera claw for this particular image, then, no matter how inaccurate the pitch of the perforations, the image will be correctly positioned in
33、the aperture. Similarly, each image on the film will in turn be correctly positioned in the aperture and, although the film has irregular perforation pitch error, the projected picture will be steady. Furthermore, any lengths of film, with their own, and different, perforation pitch errors, if taken
34、 in a camera in which the claw operates in the same perforation as does the projector claw, will be projected as a steady picture. But this condition can only result if the camera claw and the projector claw operate in the same perforation relative to the aperture, and to ensure that all films taken
35、 by any camera whatsoever and projected on any projector shall be shown with a steady picture, it is imperative that there should be a single universally recognized relationship for the displacement (number of perforations) between the claw and the picture aperture in all cameras and projectors. The
36、 purpose of this British Standard is to establish such a relationship.BS5550-1.3.3:1980 BSI 02-2000 5 The foregoing explanation is based on a reversal film. Similar conditions apply however in the case of positive films printed from negative films if, in printing, the negative and positive films mov
37、e together without related movement. In order that this may be achieved in step printers the same relationship between claw and aperture must exist. This standard applies therefore to step printers as well as to cameras and projectors.BS 5550-1.3.3: 1980 BSI 389 Chiswick High Road London W4 4AL BSIB
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