Stability and recommended storage practices for new image media
Alan R. Calmes · Portuguese National Funding Agency for Science, Research and Technology (RCAAP Project by FCT) · 1992
The first medium used to record an image was a cave wall.Parchment and paper followed much la ter.Paper as a carrier of image data has held up well during the past 500 years.Some papers have lasted longer than others as a result of chemical composition and conditions of storage and usage.Photographic pi ates and films em e r ged in the 19th Century.The .requirements of a flexible base material for motion picture film brought about the use of cellulose nitrate film.Silver halide suspended in gelatin proved to be a stable recording material for photography.Cellulose nitrate gave way to cellulose acetate by mid-20th Century and calor dyes replaced 351 silver halide in many films.By 1990, polyester w as the preferred film base for images that had to have a long life.Image stability of photographic film continues to be irnproved.If processed and stored correctly, a photographic filrn image should last 500 years.Recording of images by signal processing evolved from sound recording technology.At first, sound recordings were soundwaves reproduced by analogous physical bumps in a spiral groove.The vibrations produced on a stylus, when dragged across the bumps, simulated the original sound.L ater, sound recordings were magnetic signals in metal particles on a thin strip of filrn.The frequency .modulations of the magnetized particles produced electronic signals which could activate a loud-speaker magnet and thus replicate the original sound.Magnetic tape evolved frorn this technology.Gamrna ferric oxide bound in polyurethane painted on polyester proved to be an effective systern for the rnanufacturing of rnagnetic tape.Video recording technology evolved out of the sound recording rnagnetic tape technology.The magnetic signals represented irnage information as well as sound.It took many tracks at first to include ali the data necessary to reconstruct moving images.ln the late 1950s, lhe first video tapes were 2 inches wide.Eventually, the format was reduced to 1/2 inch wide tape.352 ~ •' ' During the past ten years the use of video tapes has grown exponentially.The U. 5. Federal Government's expenditures on video productions are now greater than on motion picture productions.The huge consumer market for VCRs has given rise to the widespread use of home vídeo cassettes for television recording and rental tape libraries.Low-cost, light-weight vídeo carne r as are now replacing h orne movíe film cameras.Magnetic tape is replacing motion picture film as the preservation medi um for memorable events r such as weddings and bírthdays.Users of vídeo tape r however r are not being warned that video images may not last as long as those on motion picture film and that neither new machines necessary to read the old tapes nor spare parta for old machines will be available 25 years from now.Computer tape copied the manufacturing methods developed for sound recording and vídeo tapes.One-half inch wide tape became the standard for computer tape early in its history and remains the standard width of compu ter tape.As ín sound and video, cartridge compu ter tape systems are dísplacing open-reel systems.Mas ter sound recordíng platters were acetate coated glass r metal and vinyl dísks.Mass produced r stamped-out, ali vinyl records domínated the commercíal market for about 5 decades.Both video and cpmputer technologies h ave copied the disk concept of • sound recordings.