Unscientific American

Date: Fri, 3 Feb 1995 10:15:12 -0500
Sender: Association for Moving Image Archivists
From: Jim Wheeler <Jimwheeler@AOL.COM>

The January Scientific American article "Ensuring the Longevity of Digital Documents" is very unprofessional and several people and organizations are writing letters to Scientific American about it. My letter is too long to be published in Scientific American but I want the Editor to understand the issue. I also enclosed a copy of my paper "Videotape Preservation".

Jan 30, 1995
Scientific American
415 Madison Ave
New York, NY 0017-1111

Dear Editor,

I have been a continuous subscriber to Scientific American for the past 40 years, and I have always considered your articles to be both scientific and understandable. I was shocked to read an article in the January edition that has several gross scientific errors in it. The author of the article "Ensuring the Longevity of Digital Documents" may be an expert on digital processing, but he certainly is not knowledgeable about the permanence of magnetic media.

Mr. Rothenberg lists the lifetime of magnetic tape as one year. I have been an archival tape engineer for over 30 years and I can say that is absolutely false! The National Institute of Standards and Technology (previously known as the National Bureau of Standards), the National Media Lab, the Battelle Institute, Ampex, and Sony have performed life tests on tapes and a 20 year life expectancy is considered reasonable for magnetic tape. Personally, I have family tapes 47 years old that play today without any special treatment or handling.

I suspect that the author is confusing failure to play back data properly with the failure of the tape itself. These are two completely separate issues! To explain the difference, I will use the common VHS videotape format as an example. JVC introduced the VHS format in 1976 and it is now the most used videotape format in the world. The term format is used to define the width of the tape, the speed of the tape, the width of the video tracks, the method used to record the signal on the tape, etc. In short, all of the specifications needed for someone to build a tape machine to play that particular tape. Videotape formats are documented and controlled by the Society of Motion Picture and Television Engineers (SMPTE). In the case of VHS, SMPTE has documented VHS as the "H" format.

What has happened with the cheap and popular VHS format, is that some companies are using the consumer VHS machines to record digital data. These consumer machines are mass-produced at the rate of about a million per month and they are not built for durability or for high-quality recording/playback.

Using VHS machines incorrectly and for a purpose for which it was not designed has given videotape (and digital) a bad reputation. A dropout for video occurs in a flash and the eye may not even notice it. But, for data, a dropout might cause a multi-million dollar mistake. Consumers who use VHS machines for video will tolerate slightly degraded playback quality and occasional dropouts in the picture. That's what you get for a $500 videotape recorder. On the other hand, professional tape recorders are precision machines built to a very high standard of performance, but the price is $40,000 to $100,000.

There are other errors in the article:

  1. The idea of copying a tape every year is absurd. If the problem is with the format, then I suggest copying the information to a proven format. That will require only one copy, not one every year!
  2. There are no common magnetic fields strong enough to erase magnetic tapes and discs, unless the media is purposely placed next to a magnet. This concern keeps being repeated by people who do not understand magnetics.
  3. Digital is better than analog for long-term storage of data. This is because analog recordings lose some information each time they are copied, and there is no way of quantifying the quality of an analog recording. With digital (recorded on a professional tape recorder), the copy is a clone of the original. Also, with digital, the raw error rate can be monitored and a copy can be made when the uncorrected error rate exceeds an undesirable level. The copy is made using error correction.

The magnetic information recorded on the tape will last hundreds of years.

The common reasons for tape deterioration are:

  1. Physical damage to the tape--usually caused by a faulty tape recorder.
  2. Storing the tape in a high humidity and/or high temperature environment.

    Magnetic tapes and discs should not be exposed to a temperature over about 80 &176;F or a humidity over about 50 % RH for very long because this can cause the binder to degrade.

I do agree with the author on one thing, and that is the problem of format obsolesce. ALL high density media have the problem of becoming obsolete after a few years because someone will develop a new method of packing more data into less space and at a lower cost. Today, there are data tape recorders that can record the entire Encyclopedia Britannia on one cassette!

I should point out that ALL forms of high-density data storage media have a limited physical life as well as a limited format life. Gold-plated CD's should last hundreds of years, but finding a working CD player in the year 2050 will be extremely difficult. So, just as you must copy your 45's and LP's because record players are now obsolete, all archival information must eventually be copied to a new format.

Also, ALL forms of data storage (not just magnetic media) must be stored in a COOL & DRY environment to prevent it from deteriorating. This is true for film, books, and CD's, as well as magnetic media.

I am a member of a American National Standards Institute (ANSI) committee and also a SMPTE committee which are developing standards for long-term storage of magnetic media.


Jim Wheeler

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