1、BRITISH STANDARD BS ISO 12606:1997 Cinematography Care and preservation of magnetic audio recordings for motion-pictures and television ICS33.160.30;37.060.20BSISO12606:1997 This British Standard, having been prepared under the directionof the Consumer Products and Services Sector Board, was publish
2、ed undertheauthority of the StandardsBoard and comes into effect on 15 September1997 BSI09-1999 ISBN 0 580 28445 X National foreword This British Standard reproduces verbatim ISO12606:1997 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technic
3、al Committee CPW/36, Cinematography, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and
4、European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI S
5、tandards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsib
6、le 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 front cover, pagesi andii, theISO title page, pages ii to iv, pages1 to9 and a back cover. This standard h
7、as been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBSISO12606:1997 BSI 09-1999 i Contents Page National foreword Inside front cover Foreword
8、iii Text of ISO12606 1ii blankBSISO12606:1997 ii BSI 09-1999 Contents Page Foreword iii 1 Scope 1 2 Normative reference 1 3 Storage hazards and concerns 1 4 Summation of storage recommendations 1 5 Derivation of recommended storage conditions 2 6 Chemical stability 2 7 Magnetic corruption 3 8 Physic
9、al distortion 3 9 Preparation of media for storage 4 10 Removal of media from low-temperature storage 4 11 Preparation for reproduction after storage 4 12 Preservation of deteriorating recordings 5 Annex A (informative) Additional data 6 Annex B (informative) Bibliography 7 Figure A.1 Cross-section
10、of magnetic recording media (schematic) 6 Table 1 Storage conditions 1 Table A.1 Diversity of analog audio magnetic records 7 Descriptors: Cinematography, motion-picture film, audio data, sound recording, magnetic recording, storage, preservation, stabilization.BSISO12606:1997 BSI 09-1999 iii Forewo
11、rd ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technic
12、al committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of el
13、ectrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least75% of the member bodies casting a vote. International Standard ISO12606 was prepare
14、d by Technical Committee ISO/TC36, Cinematography. Annex A and Annex B of this International Standard are for information only.iv blankBSISO12606:1997 BSI 09-1999 1 1 Scope This International Standard recommends storage conditions for stabilization and preservation of magnetic audio recordings for m
15、otion-picture and television production. It recommends the desirable storage conditions for magnetic audio recordings, as they may remain in library or vault storage between periods of intermittent reproduction or duplication. It describes the care and handling of magnetic media intended to be intro
16、duced into, or removed from, storage. 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the edition indicated was valid. All standards are subject to revision and p
17、arties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ANSI/NAPM IT9.11-1993, American National
18、Standard for Imaging Media Processed Safety Photographic Films Storage. 3 Storage hazards and concerns Useful and acceptable reproduction of records removed from inactive storage requires attention to, and precautions against, all three of the following hazards: chemical degradation, physical distor
19、tion, and magnetic corruption2,3,10,11,23. Analog and digital recordings are on media with the same susceptibilities to chemical degradation and physical distortion. They do respond somewhat differently to magnetic corruption effects. The recommendations for storage conditions minimize each of these
20、 risks. 4 Summation of storage recommendations 4.1 Desired useful life of the recordings 4.1.1 Medium-term storage conditions Storage conditions suitable for the preservation of recorded information for a minimum of ten years. 4.1.2 Extended-term storage conditions Storage conditions suitable for th
21、e preservation of recorded information having a permanent value. 4.2 Recommended storage environments Atmospheric temperature and humidity conditions for magnetic media storage are summarized and tabulated in Table 1. Table 1 Storage conditions Medium-term Extended-term Equilibrium temperature, C Eq
22、uilibrium relative humidity,% Alternative1: Temperature, C Alternative1: Relative humidity,% Alternative2: Temperature, C Alternative2: Relative humidity,% 23max. 2045 20max. 2030 15max. 2040 10max. 2050 Physical status: Winding Enclosure Roll orientation Co-planar Protective Vertical Co-planar Prot
23、ective Vertical External magnetic field DC: Oe AC: Oe 50max. 10max. 50max. 10max.BSISO12606:1997 2 BSI 09-1999 5 Derivation of recommended storage conditions The values in Table 1 have been derived from the extensive practical experience with photographic films, as recommended by ANSI IT9.11 for the
24、 minimization of various degradations in monochrome photographic films. Most of the same polymers and modifiers are the major components of magnetic media. Existing data on magnetic media show that the two media are subject to the same degenerative reactions, with reaction rates that are similarly c
25、ontrolled by storage conditions10,11,23,30. 5.1 Application of the recommendations of Table 1 5.1.1 Cycling Cycling of temperature and/or humidity increases the severity of the storage conditions, and should be minimized. 5.1.2 Environmental purity Control of air-entrained solid particles and gaseou
26、s impurities such as sulfur compounds, acidic vapors, ozone, peroxides, nitrogen oxides, ammonia, etc. are observed to accelerate chemical degradation. 5.1.3 Alternative storage recommendations For extended-term storage, the three correlated temperature/humidity environments of Table 1 provide essen
27、tially equivalent protection to the media. The choice among the three may be based upon convenience and existing structures. 6 Chemical stability The stability of the organic carrier-matrix bearing the magnetic particles must hold the composite in its as-recorded structure to maintain the reproducib
28、ility of the record. Although specific audio magnetic records may incorporate additional chemical compounds not normally found in processed photographic films, it is perhaps fortunate that the chemical stabilities of the major components are controlled by the same environmental factors, thereby just
29、ifying parallel recommendations. 6.1 Moisture content and temperature of the media All of the studies on chemical stability confirm that it is the precise moisture content and temperature of the actual media that controls the stability2,10. When first placed in storage, the media may require conside
30、rable time to equilibrate to the surrounding storage environment. 6.1.1 Equilibration rates A compact roll of tape or film can achieve temperature equilibrium with its environment rather quickly, but can achieve moisture equilibrium only by the slow molecular diffusion of moisture into or out of the
31、 face of the roll, all the way to the midplane of the tape or film32. 6.1.2 Media enclosures Media in storage should be in a protective enclosure or in a cassette. Such enclosed recordings will require even more time to achieve a different equilibrium relative humidity. 6.2 Nature of chemical instab
32、ilities 6.2.1 Polymeric hydrolysis A major chemical degradation mechanism for most of the organic compounds present, both in photographic films and in magnetic recording media, is hydrolysis paced by the moisture content and temperature of the medium and possibly also catalyzed by some industrial po
33、llutants 1) 3,4,10,28,29. 6.2.2 Magnetic particle chemical stability The inorganic magnetic materials in the media may include oxides of extended thermodynamic stability, or metallic elements potentially subject to oxidation which is also facilitated by increased moisture content and/or increased te
34、mperature23,26,27,30. 6.3 Optimum extended-term storage Inasmuch as the rate effects of temperature and of equilibrium relative humidity (i.e.actual moisture content of the media itself) upon chemical degradation are cooperative, it is desirable, when maximum useful life of the recordings is importa
35、nt, to attempt reconditioning of the media before storage and to store at the lower range of recommended relative humidities and temperatures. 1) The actual moisture content of the media, either photographic or magnetic, increases with increasing partial pressure of water in the atmosphere (the abso
36、lute humidity), and decreases with increasing temperature of the medium. For most materials of interest over temperature ranges near “room temperature,” this relationship, by pure chance, correlates approximately with relative humidity of the atmosphere. Thus ANSI IT9.11 and related guides recommend
37、 equilibrium relative humidity ranges.BSISO12606:1997 BSI 09-1999 3 7 Magnetic corruption Magnetic recording is a reversible process and the magnetic pattern representing information in a record remains capable of alteration by subsequent exposure to an appropriate magnetic field. 7.1 Environmental
38、effects on magnetic corruption All mechanisms contributing to magnetic corruption increase in activity and significance with increasing temperature. 7.1.1 Temperature effect The temperature recommendations of Table 1 have been chosen for minimizing chemical degradation over several years storage. El
39、evated temperatures limited to several weeks, or even days, however, can induce magnetic corruption, and should also be avoided. 7.1.2 Thermal energy effects Randomized distribution of thermal energy among the particles over time can, with some probability, assist additional particles to change thei
40、r magnetic sense, possibly even as directed by the juxtapositioned fields of the recording itself 7.1.3 Magnetic field effect External magnetic fields provide an additional potential for magnetic corruption of the recordings. 2) 7.1.3.1 External DC fields with a magnitude no greater than50oersteds(4
41、kA/m), acting upon audio magnetic records in storage, have generally shown no degrading effect upon analog or digital recordings. 3) 7.1.3.2 External AC fields are capable of assisting a larger number of particles to change magnetization sense, and therefore the somewhat lower AC field level of10oer
42、steds(800A/m) should be observed. 7.1.3.3 External fields not only increase the level of the noise floor, but also increase the print-through effect (see7.2.1). An external AC field has been shown to be particularly effective in accelerating growth in the level of the printed signal. 7.1.4 External
43、magnetic fields External magnetic fields are most frequently observed near motors and transformers (mercial building elevator installations). Most of these installations are localized and therefore the field intensity falls off rapidly with separation; a few feet of separation from the source may pr
44、ovide protection. External fields of a more unanticipated nature may be produced by audio speakers, by cabinet latches, by magnetized tools,etc. 7.2 Analog recording mode Analog audio recordings strive for a signal-to-noise ratio of60dB-80dB and are therefore most sensitive to low-level corrupted in
45、formation. 7.2.1 Print-through is a significant problem in the storage of analog magnetic audio recordings. The imprinting field that is acting upon the most susceptible particles is coming from the adjacent layer of the recording itself. The “added noise” is thus not random but recognizable music o
46、r dialog, and therefore most distracting. 7.3 Digital recording mode Digital audio recordings provide quality reproductions from magnetic signal-to-noise ratios of about20dB. Accordingly, the reputed insensitivity of digital recordings to magnetic corruption has some foundation, but since digital sy
47、stems usually take advantage of higher information densities, and work close to the limiting ratio, the margin may not be as great as is generally assumed. 8 Physical distortion Reproduction of magnetic recordings (as well as the original recording process itself) requires consistent, intimate conta
48、ct of the magnetic head with the media surface. Physical distortions interfere with achieving this requirement and thus degrade the reproduction. 8.1 Plastic flow The deformation thresholds for plastic materials such as magnetic recording media are greatly dependent upon time. The yield point stress
49、, beyond which nonelastic and irrecoverable deformation occurs, will be nearly as high as the break stress for suddenly applied shock loads and may be nearly zero for stresses maintained over a period of years. 2) The earths magnetic field is of the order of one oersted(80A/m) and is below the level of concern. 3) Magnetic flux meters reading in this range have recently become commercially available at prices an audio archive could consider. Most meters read in gauss (technically the field induced in the meters sensor). This is nu
