Unit 6 Media Resources for Libraries and Their Preservation

UNIT 6 MEDIA RESOURCES FOR LIBRARIES AND THEIR PRESERVATION

Structure 6.0 Objectives 6.1 Introduction 6.2 Types of Media Resources 6.3 Paper (Print) 6.3.1 Care, Handling and Storage 6.4 Film 6.4.1 Filmstrips 6.4.2 Slides 6.4.3 Cinefilm 6.4.4 Microforms 6.4.5 Care, Handling and Storage 6.5 Magnetic 6.5.1 Audio Tape 6.5.2 Video Tape 6.5.3 Storage Disks 6.5.4 Care, Handling and Storage 6.6 Plastic 6.6.1 Transparent Plastics 6.6.2 Vinyl Discs 6.6.3 Optical Storage Systems 6.6.4 Care, Handling and Storage 6.7 Summary 6.8 Answers to Self Check Exercises 6.9 Keywords 6.10 References and Further Reading 6.0 OBJECTIVES

After going through this Unit, you will be able to: • familiarise yourself with the various media resources available in libraries; • categorise the media resources according to their forms; • understand the different formats of non – book materials and their capacity in terms of memory; and • know the preservation methods of various types of media resources. 6.1 INTRODUCTION

It is generally agreed that the functions of library are collection, preservation, 139 Media Resources organisation and use of documents. Now-a-days libraries, apart from the traditional documents like books, periodicals, pamphlets, charts and folders etc., have varieties of non – book materials (e.g. filmstrips, microforms, CDs, DVDs, etc.) made of film, magnetic and optical which can store large amount of information. In the modern information society, libraries and information centres play a pivotal role in providing information to the users in different formats. It is therefore, essential for Librarians and Information Providers to be conversant with the latest developments of library automation, digitisation, electronic resources, internet etc. for the quick dissemination of information and services to the users. In this Unit, we shall discuss about the media resources for libraries, their types and their preservation aspects. 6.2 TYPES OF MEDIA RESOURCES

The media resources for libraries can be categorised into four types according to their forms. They are paper, film, magnetic, and plastic. Shown below are the different types of media resources available in libraries. Media Resources

Paper (Print) Film Magnetic Plastic

Books Filmstrips Sound Tape Transparencies Periodicals Slides Video Tape Vinyl Discs Dictionaries Cinefilm Storage Discs Optical Storage Directories Systems Encyclopaedias Folders Pamphlets Brochures, etc. We shall discuss one by one, in detail, about their formats, physical size, capacity in terms of memory etc. in the forthcoming sections. Self Check Exercise 1) What are the major categories of media resources? Note: i) Write your answer in the space given below. ii) Check your answer with the answers given at the end of this Unit...... 140 Media Resources for 6.3 PAPER (PRINT) Libraries and Their Preservation Though this Unit is basically on non-print media, you need to be familiarised with the printed documents available in traditional libraries and their preservation aspects as well. Paper is still one of the predominant medium for storing and transmitting information the world over. Paper based collections available in traditional libraries include books, periodicals, dictionaries, encyclopedias, glossaries, bibliographies, yearbooks, handbooks, directories, biographies, gazetteers, atlases, maps, brochures, folders, pamphlets, etc. 6.3.1 Care, Handling and Storage

The following points can be considered for the care and maintenance of the paper collections: • Poor quality paper deteriorates rapidly in sunlight. It can be avoided keeping out of the light. • Paper surfaces and edges damage easily with handling. Various protective devices such as lamination, edge binding and the like can reduce these problems. • Printed sheets which are produced by spirit duplication generally fade in light. Copies, which are stored, should be kept out of the direct light to minimise these problems. • Dirt and grease from fingers can damage paper collections. It can be cleaned with an ordinary eraser. Self Check Exercise 2) List out any five kinds of print materials/documents available in traditional libraries. Note: i) Write your answer in the space given below. ii) Check your answer with the answers given at the end of this Unit...... 6.4 FILM

Films are available in different formats viz. filmstrips, slides, cinefilms and microforms. Let us discuss in detail, their physical formats, size, memory etc. 6.4.1 Filmstrips

Filmstrips are made up of a series of still pictures placed in sequential order on 141 35 mm filmstrips, which are available in two different formats. The formats Media Resources are single or half frame, and double or full frame. The still pictures, which are stored in filmstrips, can be viewed only using projector or viewing equipment. The visuals of single frame filmstrip are photographed in a vertical plane (see Fig. 6.1) and that the ratio of picture or frame height to width is approximately 3 to 4, whereas the double frame filmstrips are photographed on a horisontal plane, and the height width ratio is 2 to 3. The following figure shows the differences between single and double frame filmstrips.

Fig. 6.1: Filmstrips: Single Frame (a) and Double Frame (b) (Source: Cabeceiras, 1982) 6.4.2 Slides

Slides are small units of transparent material containing an image mounted on a rigid format and designed for use in a slide viewer or projector. A mount made of cardboard or plastic is used to hold the film. Sometimes glass is used to cover and protect the film within the mount. Slides are something different from filmstrips. They are individually mounted, and still visuals are stored on separate pieces of transparent film, whereas filmstrips can contain a group of still pictures on a continuous piece of transparent film. Various sizes of the slides and films that can be contained in the slides are listed in Table 6.1. Table 6.1: Sizes of slides and the films for slides

Sl. Size No. in inches

1. 2 x 2

2. 2 ¼ x 2 ¼ 3. 3 ¼ x 4

Out of these three sizes mentioned above, 2 x 2 inch size is the most prevalent size used in libraries. This mount or frame can contain 35 mm half frame film, 35 mm full frame film or 127 size film. These three sizes of films have the 142 same size mount and can be viewed using the same type of projection equipment. Moreover, the 2 ¼ x 2 ¼ inch frame and 3 ¼ x 4 frame can contain Media Resources for 110 film size and 120 film size respectively. Fig. 6.2 illustrates the various Libraries and Their sizes of slides. Preservation

Fig. 6.2: Various sizes of slides (Source: Cabeceiras, 1982) 6.4.3 Cinefilm This is the most popular medium to distribute films for public. Cinefilm means as, “a sequence of images arranged vertically, which gives the appearance of movement when projected on to a screen at the right speed”. Various formats of cinefilm are discussed below. • 35 mm with sound track: This format is generally used in public cinemas. There is also a double sized frame that means 70 mm size, which is used for major productions. 16 mm with sound track: This is the format, which is used for distributing films to small clubs, schools and businesses. The film can be projected at 24 frames per second, a reel of 40 ft. (i.e.120m) lasting about 11 minutes (36 ft. or 11m per minute).

Fig. 6.3: 35 mm and 16 mm films with sound track 143 Media Resources The sound track is usually optical, being a white stripe down the side as shown in Fig. 6.3. In some films the white stripe is replaced by a brown stripe which is the same as a thin piece of sound tape. This carries a magnetic sound track with all the properties of magnetic tape, and it can usually be erased. Optical sound tracks cannot be altered in this way. • 16 mm silent: This film has sprocket holes on both sides without white stripe down as in 16 mm film to produce sound. The film should be projected at 18 frames per second, a reel of 400 ft (120m) lasting about 16 minutes (i.e. 24 ft. or 7m per minute). 8 mm standard and 8 mm super film: Earlier, standard 8mm film was the only type of 8mm film available. Later, the sprocket holes which appear in left edge of the films, as shown below in Fig. 6.4, were designed for 16 mm film and equipment, and it became apparent that 8 mm film actually did not need such large sprocket holes in order to function properly. Hence, super 8 mm film was designed with much smaller sprocket holes, and the extra space resulted in a 50% increase in the size of the picture area.

Fig. 6.4: Standard 8 mm and super 8 mm film formats (Source: Cabeceiras, 1982) From the figure, we can see that the widths of both the standard 8mm and the super 8mm films are same. But the size of the sprocket holes of standard 8 mm (3mm) is twice as wide as that of super 8 mm (1.5mm). Sprocket holes of standard 8mm film are located on where the frames meet, whereas on super 8mm film the sprocket holes are adjacent to the middle of each frame. As a result, when projected, the super 8mm film produces a clearer, sharper picture than the standard 8mm film which is now considered obsolete. 6.4.4 Microforms

When categorising media, the microforms can truly be considered a hybrid. It is the amalgamation of both the print and non print media in that it makes print information available on a film format. Microform is a generic term for all media of communication used to store miniaturised text or microimages on film or paper. It cannot be utilised or read without magnification. It can be grouped into two categories: a) Serialised (roll) microforms; and b) Unitised microforms.

144 Serialised Microforms Media Resources for Libraries and Their Serialised microforms store images sequentially on a continuous roll film. Preservation One has to pass through all the images (before it on the roll), to locate an image. This category includes open reels, cartridges, and cassettes (see Fig. 6.5). Open Reel Microfilm: It is a continuous roll of 16mm or 35mm photographic film that wraps around a spool. It is used to store a large amount of miniaturised text and/or microimages which can be magnified and copied only with the aid of a traditional reader/printer or a reader/scanner. It usually comes in 100 foot lengths, though it can come in lengths of up to 215 feet. Microfilm Cartridge: It is simply a roll microfilm which has been placed in a compact plastic holder, that is self – threading in compatible retrieval equipment. It requires special insertion and material equipment. It protects the film from fingerprints and dust. Cassette: like a cartridge it houses a roll of microfilm but different in that it contains both a feed and take – up reel. The main advantage of a cassette is that the film does not have to be rewound before it is removed from a reader, and the image can be kept in position for later viewing.

Fig. 6.5: Serialised Microforms (A) Open reel microfilm (B) Microfilm Cartridge Unitised Microforms Unitised microforms are images that are cut or created in units and placed in special holdings. It is possible to locate each image directly. This type of microforms include microfiche, aperture cards, and jacketed microfilm (see Fig. 6.6). Microfiche: It is a card shaped sheet of photographic film, usually 3 × 5 or 4 × 6 inches in size designed to store miniaturised text and/or microimages that are arranged in standardised columns and rows. Microfiche can be produced from duplicated jacketed microfilm, from source documents using a step – and – repeat camera, and from Computer Output Microfiche (COM). On a fiche, 98 pages at a reduction ratio of 24x and 270 pages at a reduction ratio of 48x can be fitted. It is possible to read the title without magnification as the top of the microfiche sheet contains identification information like jacketed microfilm. Aperture Cards: An aperture card is a keypunch card with a rectangular window with either one frame of 30mm or several frames of 16mm microfilm inserted into the window. The microfilm is directly affixed to the card or it may be 145 Media Resources inserted into a thin jacket which is itself fixed to the card. The size of the card is generally 187 × 82 mm. These cards are mostly used for large engineering drawings. Jacketed Microfilm: A microfilm jacket is a fiche sized acetate or polyester carrier. It contains 3 to 8 sleeves or channels into which strips or single images of either 16mm or 35mm roll films are inserted. One jacket can hold up to 60 images. It can be used for records that are frequently updated. Because a jacket allows a file to be updated, and the new materials can also be inserted into the unused channels.

(A)

Fig. 6.6: Unitised Microforms (A) Microfiche (B) Aperture Cards (C) Jacketed Microfilm 6.4.5 Care, Handling and Storage

Good care and maintenance of film materials, which are concerned with the following points, constitute the basic procedures for their long-term preservation. Care • The films should be changed and inspected after each use. This can be done by using soft brush or puffer. The items, which are not frequently used, should be inspected regularly and rewound at intervals. • The equipments used for screening/display must be kept clean and dust free. Handling • In handling, films should not be jarred or dropped. This may produce scratches. • Use of bent containers or reels should be avoided. This can damage films severely. • Films should not be handled only by the edges, and should not be twisted. • Film materials taken out of the air conditioned storing, should be allowed to reach room temperature before these are screened/displayed. • Film materials should be projected/viewed only by equipments mounted safely. • Only qualified staff should be allowed to handle the media and the equipments. 146 Storage Media Resources for Libraries and Their • Film materials should be stored away from sunlight, which has bleaching Preservation effect. In sunlight colours fade with prolonged exposure. • Films should be stored in dust free containers. The polyester base attracts dust which damages the film surface. • The containers should not be composed of materials harmful to film materials, such as those having acidic, sulphur or peroxide contents. • Films under glass cover should be absolutely dry. • High humidity encourages bacterial and fungal growth in photographic emulsions and high temperature affects films badly in the long run. Relative humidity should be from 45 – 50 per cent and temperature around 20 – 22 degree Celsius. Self Check Exercises 3) What is serialised microform? Identify the formats. 4) List out the points to be considered for the storage of film media. Note: i) Write your answers in the space given below. ii) Check your answers with the answers given at the end of this Unit...... 6.5 MAGNETIC

Magnetic tape is discussed under two main divisions: audio and video in this section. 6.5.1 Audiotape

Audiotape is the most appropriate medium for music recording. Besides music, many types of information like lectures, debates, speeches, poetry readings, book talks, interviews etc. can be expressed through this medium. Tapes are made of plastic and coated with a layer of ferric oxide or chromium oxide. The plastic is either an acetate or polyester. Audiotapes are available in various playing speeds and recording formats (monaural, stereophonic, and quadraphonic) as well as various tracking configurations (2 track and 4 track). Tapes are commonly available in two formats: open reel and cassette. Open reel: The open reel was the first format available, and it is gradually being replaced by the cassette and cartridge. Tape reels are available in various sizes, 3, 4, 5 and 7 inches in diameter. Each size can hold twice as much tape. 147 Media Resources A 3inch (7.62cm) reel will hold 150 feet (45.7m) of 1.5 mil tape, a 4 inch (10.16cm) reel 300 feet (91.4 m), a 5 inch (12.7cm) reel 600 feet (182.9m) and a 7- inch (17.8 cm) reel 1200 feet (365.8m). All reels accommodate a tape that is ¼ inch (0.63 cm) wide. Playing times of these sizes are listed in Table 6.2.

Table 6.2: Playing Times of Audio Tape (Single track)

Reel Tape diameter length (inch/cm) (feet/m)

3/7.62 150/45.7 4/10.16 300/91.4 5/12.70 600/182.9 7/17.80 1200/365.8 Casette: It was first developed by Philips during the 1960s. The standard dimension of audio cassette is 10.2 × 6.4 cm. It can be categorised into two types according to its formats: reel-to-reel cassettes and loop cassettes or cartridges. The audio cassette tape is approximately 0.39 cm wide. It is reel to reel in design, which permits tape to be advanced or rewound at high speed. The recorders and players for cassette run at a standard speed of 4.76 cm per second. The cartridge tape is 0.63cm wide. It being a loop, operates only in one direction and at one speed. Cartridge tapes generally run at a speed of 9.52 cm per second. Both the cassettes and cartridges are simply inserted into the tape recorder, and are ready to be played. The inner side of the cassette has been illustrated in Fig. 6.7. Cassettes are labeled with a capital letter C followed by a number, such as C15, C30, C45, C60, C90, C120, which means that cassettes are sold with predetermined playing times. These are C30 (15 minutes each side) C60 (30 minutes each side) C90 (45 minutes each side) and so on.

1) Gearing of the left – hand supply reel 6) Felt pad 2) Left – hand supply reel 7) Baffle 3) Guide roller 8) Capstan 4) Guide pin 9) Gearing of the right – hand take – up hub 5) Pressure spring 10) Inspection window. 148 Fig. 6.7: Inner side of the cassette (Source: Fothergill, 1990) Digital Audio Tape (DAT) Media Resources for Libraries and Their This is the latest addition to the tape family and it is used in the computer for Preservation storing processed data, backing up data stored in disks and interchanging programs and data between organisations. DAT cassettes are much smaller 7.2 × 5.4 × 1cm (2.8 × 2.1 × 0.4 in), although the tape itself is the same width, 3.8mm (0.15 in). They are available in 60, 90 and 120 minutes lengths, although at long-play speed, they can last twice as long, i.e., up to 4 hours. The cassette itself is enclosed, completely covering the tape, and insertion into the machine pushes back a cover and lifts a lid to reveal it. Accidental eraser is prevented by moving a small slider on the back. When the hole is open, no recordings can be made. 6.5.2 Videotape Videotape is made of chromium dioxide or metal as the major constituent of the magnetic coating. Like all other magnetic tapes, which have been discussed earlier, videotape can also be used to record digital information for computer related equipment. Videotape is normally available either in open reel or in cassettes like audiotape. Let us discuss in detail the differant types of video tapes. Open Reel Videotape: Open reel videotapes are available in ¼, ½, 1 and 2 inch widths. 2-inch videotape is used for broadcasting. 1-inch videotape is mostly used for studio production, ½ inch tape is the most popular open reel format for localised viewing and ¼ inch tape is as good as ½ inch videotape. Out of these videotapes, 1 inch is the most widespread one which is used for professional recording and for many broadcast purposes. Videocassette: Videocassettes containing ½ and ¾ inch videotape are realising tremendous growth. Now, there are only three systems active in use : U-Matic, which is mainly confined to professional use; VHS, the common system; and 8mm video which is used in a number of semi-professional cameras. U- Matic cassette was the first videocassette format designed, and intended primarily for industrial and educational use. It uses 19.05 mm tape at a speed of 9.5 cm per second in containers, 221 × 140 × 32mm. They are available with varying lengths of tape providing recording times of 10, 15, 20, 30, 40, 50 and 60 minutes. VHS cassette uses 12.65 mm tape at a standard speed of 2.34 cm per second in containers, 188 × 104 × 25 mm. They are available with varying lengths of tape providing recording times of 30, 60, 90, 120, 180 and 240 minutes. VHS- C is a much smaller cassette which can be used in cameras to make recording, and S-VHS is a new development to improve the quality of the recording and playback. Cassettes using the small 8mm tape are 9.2 × 6.2 × 1.4 cm. The tape is totally enclosed when not in use, the flaps at the front of the container parting is opened when placed in the equipment. Playback of 8mm cassettes is generally either through a television set attached directly to the camera or through dubbing to a conventional video recorder.

149 Media Resources Fig. 6.8 shows the various videotape formats available.

Fig. 6.8: Videotape Formats (Source: Cabeceiras, 1982) 6.5.3 Storage Disks

In this section, let us concentrate on the magnetic disks which are used in the computer as the back-up storage medium for recording information or data, and programs. It can be categorised into two kinds: hard disk and floppy disk. Hard Disk Mainframe computers use disc packs, but these are stored within the computer service area. More common and increasingly available at relatively inexpensive prices, are hard discs or Winchester discs. These are smooth metal plates coated on both sides with a thin film of magnetic material. A set of such magnetic plates is fixed to a spindle one below the other to make up a disk pack (see Fig. 6.9) These are 7.5 to 20 cm (3 to 8 in) discs, kept with the reading heads in sealed, dust free containers, and are usually attached to or part of the computer itself. Storage capacity is up to 300 megabytes of data.

Fig. 6.9: Parts of Hard Disk (Source: Moulton and Stanley, 1982) Floppy Disk Floppy disks are used as secondary storage medium for storing and keeping back-up information or data stored in microcomputers. The floppy disk is made of magnetic oxide coated computer tape material. As the material used is not 150 hard plate but a flexible tape, it is called “floppy disk”. It is removable, portable, and widely used medium in libraries. Alteration, such as copying and deleting Media Resources for files or documents, can easily be done in any number of times. Libraries and Their Preservation Floppy disks are available in three formats: 8inch; 5.25inch; and 3.5inch. 8 inch and 5.25 inch floppies are now obsolete. There is also another form of a disk, about 2inch in diameter, available for recording still photographs shot with special cameras (i.e. digital cameras). About 50 pictures per disk can be stored and the playback is through a television set. The main parts of the floppy disk are shown in Fig. 6.10.

Fig. 6.10: Main parts of floppy disk (Source: Rajaraman, 2001) The disk is artificially divided, while formatting a new disk before use, into concentric tracks, each track being subdivided into sectors and each being assigned a separate code so that the computer can quickly locate it. A disk has 192 tracks, 9 sectors per track, 512 bytes on one side of the disk. The gross capacity on both sides is 1.75MB and the net capacity is 1.2MB. The rotation speed of a floppy is of the order of 366 rpm with a transfer rate of 40 Kilobytes per second. For reading and writing on the disk, the head has to be in contact with the disk surface. 6.5.4 Care, Handling and Storage

The care and maintenance of magnetic materials are concerned with the following points: Care • All tapes and discs should be played periodically to prevent the magnetic print-through of the message in other words inter layer transfer from one layer to the next. • The tapes must be flat on the reel. No part of a tape should be twisted, bent or erased. The tapes should be tightly rewound when not in use to prevent this kind of damage. • The disks should always be kept free of dust, grease and dirt, which seriously interfere with their efficient use. Handling • Tapes should be touched as little as possible, and carefully handled to avoid dropping down, which can cause irreparable damage to the tape. 151 Media Resources • The discs should always be handled tenderly. Any pressure on the disk can damage the surface. This can be caused, for example, by writing with a ballpoint pen on a label on the cover, or packing the disk into a container too densely. Storage • The temperature and humidity of the storing area should be from 17 – 20 degree Celsius and 35 – 45 per cent respectively. • Tapes should be stored in dust proof containers, to avoid accumulation of dust and dirt on and between layers of tape. • Recording on the tapes and discs is the result of magnetic process. It is important to store tapes and discs away from the influence of magnetic fields, which can be caused by high power electric motors. • Magnetic tapes should be stored in a vertical position to prevent damage. • The storage area or shelving must not be subjected to vibrations. Self Check Exercise 5) What is a floppy disk? What are the different formats available? Note: i) Write your answer in the space given below. ii) Check your answer with the answers given at the end of this Unit...... 6.6 PLASTIC

Plastic based material can be categorised into three types: transparent plastics; vinyl discs, and optical storage discs. Optical discs are now the most widely used media in IT industry and library. 6.6.1 Transparent Plastic

Overhead transparencies are extensively used in education for lecture, presentation etc. The major types of transparencies are clear acetate (on which information is drawn with a pen), thermal (heat process), and diazo(low speed photographic). The transparencies, which are used with the overhead projector, are available in various thicknesses. The thicknesses are commonly ranging from 0.05mm to 0.25mm as either single flat sheets or as rolls. The rolls are 25.4mm wide and of varying lengths, whereas the flat sheets are usually supplied in three sizes: 26.7 × 26.7cm (10 ½ × 10 ½ in.), 26.7 × 20.3cm (10 ½ × 8 in.) and 29.7 × 21cm (11 ¾ × 8 ¼ or A4). When loose sheets are kept against each other, paper should be inserted between them to reduce the natural 152 adhesion between plastic. 6.6.2 Vinyl Discs Media Resources for Libraries and Their There are two categories of vinyl discs, audio and video, discussed in the Preservation following sections: Audio Disc: Perhaps the prominent audio form is the disc recording. Discs are marketed in various sizes of 17.8cm, 25.4cm, and 30.5cm diameter sizes. The central hole for the spindle is about 7.5mm in diameter. This spindle need not be a tight fit. The disc recordings are available in three playing speeds, 33 1/3, 45, and 78 revolutions per minute (rpm). A speed of 16 2/3, called a transcription, is also available. The audio discs are now obsolete, but many libraries still have extensive collections of these discs. When playing a disc recording, a proper size needle, which is called ‘stylus’, must be used. The stylus used to play a 78 rpm record is 0.003 inches in diameter to fit a 0.003 inch record groove, whereas the stylus used to play a 33 1/3 or 45 rpm record is 0.001 inches in diameter to fit a 0.001 inch record groove. Video Disc: The videodisc is similar to an audio disc. The size and shape of the discs are same, and it has grooves. A slight difference is that the audio disc is generally black, whereas a videodisc is metallic and has an aluminized appearance. A single videodisc contains 108,000 grooves or frames (54000 on each side) and thus has the capability of storing 108,000 pages of printed text or ‘still’ information. Any particular frame can be retrieved and viewed in less than 3.5 seconds, when a disc is used on a player with an electronic accessioning function. Videodisc has already been illustrated in Fig. 6.8 (see two discs appear at last from left in back row). 6.6.3 Optical Storage Systems Various configurations of optical storage systems are: laservision, CDs and DVDs. Laservision These discs have been produced in two forms: a continuous moving picture of an hour’s duration each side without still picture facility; and a 36 minutes’ of duration each side with still picture control (i.e. individual frame/picture is easily identifiable). Two audio channels are also available on each: in the first providing stereo sound; and in the second offering selectable options such as two different languages, or sound effects on one with voice on the other. The discs are usually coloured silver, size, 30cm (12in.) in diameter and 3.4mm thick, and have a centre hole of 35mm diameter. The disc can hold 54000 individual frames or pictures. In addition, a teletext analogue is also possible, providing the option for other information. An extension of the laservision principle is known as Advanced Interactive Video (AIV). Both the visual and sound information on laservision discs are recorded in analogue form.

153 Media Resources Compact Discs In 1982, Sony recorded stereo music for the first time on a disc, called ‘Compact Disc’, transferring analog signals into a digital form. A compact disc is made of polycarbonate with one or more metal layers capable of storing digital information. Compact discs for audio were shown in 1980 and were launched commercially in 1983 by Philips and Sony. The physical size of the disc is generally 12cm in diameter, 1.2mm thickness, and 15mm hole in the centre of the disc. Different versions of the discs, which are available in the market, include CD audio, CD – ROM, CD – V, CD – I, CD – R, CD – RW etc.

• CD Audio: These are now very popular formats for distributing recordings of music. These discs are silver coloured, and the size is 12cm (5in.) in diameter, 1.2mm thickness. It has 15mm hole in the centre of the disc. Maximum playing time for one disc is approximately one hour. A smaller version, 8cm (3in.) in diameter, and the other version MP3, which can store 200 songs (approximately), are now gaining popularity for popular music. The recording is digital, and on one side.

• CD – ROM: This stands for Compact Disc Read Only Memory. It was launched in 1986. The disc, which is similar in size to audio CD, can hold 650 Megabytes of information (i.e. equivalent to about 300000 text pages of A4 size) that means an entire encyclopaedia or databases for bibliographic references viz., Library and Information Science (LISA), Science Citation Index (SCI), Aquatic Sciences and Fisheries Abstract (ASFA), etc. can be stored in one CD – ROM. At present, all CD – ROM products aim at libraries and librarians, because this is an appropriate medium for libraries to store and retrieve information, more space can also be saved.

• CD – R: It translates as Compact Disc Recordable also called Write Once CD –ROM. It was commercially available in 1989. It is made of polycarbonate, has a groove cut in it, and covered by a photosensitive dye. This layer is covered with a thin layer of gold (called reflecting layer). The final layer is a protective layer. A laser beam is used to write data. These discs are used to produce a large number of copies. The medium used is a 12 cm writable/recordable disc, and can be used in any standard CD – ROM player.

• CD – RW : This stands for Compact Disc - ReWritable. It became available in mid – 1997 and enables to write on to it in multiple sessions. One of the problems with CD – R discs is that we can only write to them once, whereas CD – RW drives and discs allow to treat the optical disc just like a floppy. These discs hold up to 80 minutes (700MB) of data, and can be rewritten as many as 1000 times.

• CD – V: The V stands for Video. These discs were commercially launched in 1989. These are available in a number of sizes with different playing times. The sizes are 12cm, 20cm, and 30mm. The 12cm (5in.) disc can carry up to 6 minutes of video with sound and a further 20 minutes of audio, all recorded like CD audio on one side only; the 20cm (8in.) up to 154 20 minutes of audio and video on each of the two sides; and the 30cm (12in.) up to 60 minutes of audio and video on each of the two sides. The Media Resources for recording formats are digital for audio, and analogue for video. Libraries and Their Preservation • CD – I: The I stands for Interactive. These discs are similar to audio CD in size and appearance. The data such as mixtures of text, graphics, audio, and still and moving pictures can be stored. The memory capacity is about 200000 pages of text, 7800 still pictures, an hour of stereo sound or nearly 20 hours of speech. The recordings will be digital only. Although the CD – I was never a commercial success, but it had its use in education, training, and other professional applications.

• CD – ROM XA: It stands for Compact Disc Read Only Memory – eXtended Architecture. This is a modification of CD – ROM which defines two new types of sectors (areas left free for extra data by the omission of error detection and correction code) that enable it to read and display data, graphics, video and audio at the same time. The other versions of CDs such as Photo CD, Video CD and CD – EXTRA have all been based on CD –ROM XA.

The following 6.11 figure shows the construction of a CD –ROM.

Fig. 6.11: CD –ROM (Source: Oppenheim, 1988) DVD (Digital Versatile or Video Disc)

The DVD is the new generation of optical disc storage technology. It has replaced the laser disc, and eventually could replace audio CD and CD –ROM. This disc holds 4.7 GB of data on one of its two sides. It is possible to store a 133 minute movie in one side of a DVD. With two layers on each of its two sides, it can hold up to 17 GB of video, audio, still photos or other information, and the access rates of 600 KBps to 1.3 MBps. Comparatively the DVD holds 28 times more data than the CD – ROM disc (see table 6.3 ). Like CD – ROMs, DVDs are also available in different physical formats such as DVD – ROM, DVD – R, DVD – VIDEO (simply called DVD), DVD – R/RW, DVD + R/ RW, DVD – RAM, DVD – VR, DVD – AR, DVD – SR, and DVD – A.

155 Media Resources Table 6.3: CD-ROM and DVD-ROM Comparison

Pit length (micron) Track Pitch (micron) Laser beam wavelength (nanometer) Capacity 1 layer/1 side 2 layers/1 side 1 layer/2 sides 2 layers/2 sides

(Source: Rajaraman, 2001) 6.6.4 Care, Handling and Storage

Care Plastic sheets are not generally used for any long lasting purpose. As long as the document printed or written on them are in need, the sheets are kept flat to avoid wrinkles. These are kept free from moisture to avoid sticking together. If several sheets are kept together one above the other, it is necessary that these are separated by sheets of paper kept in between. On the other hand, the plastic material from which disc is made is fairly strong. The major care, which the disc will need, is to protect the groove on it from dust and dirt, and to clean the surface, as well as the stylus of the player before using the disc each time. The pick up stylus physically vibrates along the groove as the disc is played. As a result, the grooves gradually wear out. This is a natural process of decay. The less number of times a disc is played, the longer it lasts. Use of worn out stylus quickens the process of decay. So the use of such a stylus should be strictly avoided. Handling Careful handling of discs to avoid their dropping down or scratching on their surface is essential. The discs should be as level as possible on the turn table when played. Storage Bending and warping due to exposure to heat and damp are very common. Such a damage may also be caused as a result of uneven pressure on the surface. Discs should, therefore, be stored in controlled temperature and humidity. Each individual disc should be placed in the paper sleeve, the opening of which should be against a sealed edge of a cardboard cover in which it is placed. The discs, so covered, are stored vertically, not leaning in either direction. It is not 156 advisable to stack several discs together, stacked one above the other. Media Resources for 6.7 SUMMARY Libraries and Their Preservation In this unit, different types of media resources, print and non – print, have been discussed. Film media, which include filmstrips, slides, cinefilm, and microforms, have been discussed in detail with figures and illustrations. Magnetic media, which include audiotape, videotape, and magnetic disks, have also been discussed. Plastic media, which include transparent plastics, vinyl discs, and optical discs (CDs, DVDs, etc.), have been explained, with suitable examples. An attempt has also been made to discuss the methods of preservation for handling and storage of all four kinds of media resources separately. 6.8 ANSWERS TO SELF CHECK EXERCISES

1) The following are the four major categories of media resources: i) Print ii) Film iii) Magnetic iv) Plastic 2) Print materials available in traditional libraries are: i) Dictionaries ii) Directories iii) Yearbooks iv) Handbooks v) Encyclopedias 3) Serialised microforms means to store images sequentially on a continuous roll film. One has to pass through all the images (before it on the roll), to locate as image. The available formats of serialised microforms are: i) open reel microfilm

ii) cartridges, and

iii) cassettes. 4) The following are the points to be considered for the storage of film media: i) Film materials should be stored away from sunlight, which has a bleaching effect. In sunlight colours fade with prolonged exposure. ii) Films should be stored in dust free containers. The polyester base attracts dust, which damages the film surface. iii) The containers should not be composed of materials harmful to film materials, such as those having acidic, sulphur or peroxide contents.

iv) Films under glass cover should be absolutely dry. 157 Media Resources v) High humidity encourages bacterial and fungal growth in photographic emulsions and high temperature affects films badly in the long run. Hence relative humidity should be from 45 – 50 per cent and temperature, 20 – 22 degree Celsius. 5) This is the disk which is used as a secondary storage medium for storing and keeping back-up of information or data stored in microcomputers. These disks are made of magnetic oxide coated computer tape material. As the material used is not hard plate but a flexible tape, it is called “floppy disk”. These are removable, portable, and widely used medium in libraries. Floppy disks are supplied in three formats: 8inch; 5.25inch; and 3.5inch. 6) A compact disc is made of polycarbonate with one or more metal layers capable of storing digital information. The different kinds of physical formats are: i) CD – Audio ii) CD – ROM iii) CD – R (Recordable) iv) CD – RW (ReWritable) v) CD – V (Video) vi) CD – I (Interactive) vii) CD – ROM XA (eXtended Architecture) 6.9 KEYWORDS

Microform : A miniature reproduction of printed or other graphic matter which cannot be read without magnification. Sound Recording : A recording on which sound vibrations are registered by mechanical or electrical means so that the sound may be reproduced. Video Recording : A recording designed for television playback, on which both pictures and sound have been registered electronically. 6.10 REFERENCES AND FURTHER READING

Cabeceiras, James (1982). The Multimedia Library. 2nd ed. New York: Academic Press. Fothergill, Richard and Butchart, Ian (1990). Non – Book Materials in Libraries: A Practical Guide. 3rd ed. London: Clive Bingley. IGNOU – MLIS – E1 (1997). Preservation and Conservation of Library Materials. New Delhi.

158 Moulton, P. D. and Stanley, Timothy S. (1989). Hard Disk Quick Reference. Media Resources for Indiana: Que Corporation. Libraries and Their Preservation Oppenheim, Charles (ed) (1988). CD – ROM: Fundamentals and Applications. London: Butterworths. Purcell, Lee (1995). Super CD – ROM Madness. Indianapolis: Sams Publishing. Rajaraman, V. (2001). Fundamentals of Computers. New Delhi: Prentice Hall of India. Weihs, Jean (et al) (1979). Non – Book Materials: The Organisation of Integrated Collections. Canada: Canadian Library Association. http://www.state.sc.us/scdah/SEVEN.PDF (accessed on 09.11.2003). http://www.dvddemystified.com/dvdfaq.html (accessed on 09.11.2003).

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