X-Message-Number: 2655 Subject: CRYONICS Videotape From: (Charles Platt) Date: Sun, 20 Mar 94 11:15:38 EST Re magnetic tape: It is true that old tapes may hold up well. I own open-reel four-track audio tapes from thirty years ago, and I can still play them. Video, however, is a different matter. The tracks are far narrower, they are recorded diagonally across the tape, and the timing of the signal is far more important. Thus, if the tape shrinks slightly, it can seriously affect the picture. By comparison, if audiotape shrinks slightly, the results are barely detectable. Another long-term problem is that the binder (which glues the magnetic particles onto the mylar tape) can deteriorate with age, with the result that metal oxide particles fall off the tape. "Print through" is also a problem, especially with very thin (long-playing-time) tapes. The coils of tape, tightly wound in the cassette, affect each other magnetically. For this reason, it's often recommended that tape should be wound and rewound periodically, to reposition the "layers" with reference to each other. Lastly, of course, tape can be demagnetized. Even if there is no interference from a magnetic field, it seems that very small fluctuations in the magnetic pattern can gradually disappear over time. I have noticed that my very old audiotapes have a poorer frequency response now than when I first recorded them (and this cannot be entirely explained by my aging hearing). For archival purposes, tape sucks. Unfortunately, however, there are no substitutes. We'll have to wait another twenty years or so for EPROMS to be big enough and cheap enough to store video. In the meantime, I suggest that archives should include monochrome photographic negatives, and perhaps color xeroxes on acid-free paper. These are two very stable ways to store images. --Charles Platt Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=2655