The following is a Plus Edition article written by and copyright by Dick Eastman.
Genealogists are generally concerned with long-term data preservation. A lot of genealogists believe that the only method of preserving data is to print the information on paper. Yet, many of us have handled old pieces of paper that are decaying, crumbling, or fading to the point that the information is not readable. In fact, most paper manufactured in the past 75 years or so contains acids that will hasten the deterioration of the information you wish to preserve.
As we have seen recently in several places around the world, paper is especially fragile. Paper documents are easily destroyed by fires, floods, earthquakes, or building collapse. On a couple of recent occasions, valuable paper documents have been lost forever due to simple burst water pipes.
In archivist circles, the preferred solution is to “digitize data so as to preserve it” and then to make multiple copies, stored in different locations. However, even digitizing requires some serious precautions and planning. Today’s common choice for long-term digital data storage is CD-ROM or DVD-ROM disks. However, the technology has only appeared in the past two decades; so, we do not yet know if these devices will store data for a century or more. Some studies indicate that the information may not last that long. In fact, there is proof that some CD-ROM disks may not even last a decade!
The main advantage of digital data is that there is no signal degradation in the output. In a digital environment, data is stored in "bits," often referred to as "ones and zeroes." Each bit either is there or it isn't. In contrast, data stored on analog media such as a magnetic tape of audio or video, is stored in an infinite number of signal strengths. This variable quality is the problem; the result of copying it, playing it, or even just storing it is degraded audio or images. In short, analog data will degrade over time; digital data will not.
Anyone who has used both analog and digital cell phones is familiar with this difference. Analog cell phones work well when signals are strong. However, as the cell phone user moves further from the cell tower being used, the signal received deteriorates, slowly introducing hiss, static, and other noises. As the signal weakens still further, the induced noise eventually overpowers the wanted signal. By contrast, digital cell phones work much better. The user does not notice any difference between a strong signal and a weak one. In each case, the reconstituted audio sounds very good in the cell phone's earpiece. If the signal strength drops even further, the excellent-sounding audio simply disappears abruptly. When using a digital cellular connection, one never hears static or the hiss of "white noise." Either the received signal is good enough for perfect sound, or it is not there at all. There is no in-between condition.
The same is true of photocopies. Using traditional photocopies or photo-reproduction technology, make a copy of a copy of a copy of a copy, and you will see that each succeeding copy becomes a bit fuzzier than the preceding image. That is analog technology. Now do the same with a digital image of a scanned document. If the original was a crystal-clear image, each and every digital copy will be the same, regardless of the number of “generations” involved.
The same is also true for audio and video analog tapes when compared to digital disks. An analog tape can deteriorate over time and with frequent use, and the hiss of white noise will grow as signal strength weakens. For instance, on video, the white noise will appear as "snow" or as a fuzzy image. The condition worsens with time and with the number of replays. Eventually, the white noise overpowers the desired signal. On the other hand, digital data as stored on CD and DVD disks operates in loosely the same manner as the digital cell phone or the digital images. The signal will appear perfect to the user for many years. When the signal finally becomes so weak as to be unusable, the result is total silence. There is never an in-between period of growing hiss or static.
Likewise, copying data to a digital medium yields higher quality audio or video than that derived from an analog tape. An audio or video analog tape that is ten years old already has some hiss on it, perhaps a lot of hiss if an inexpensive tape was used. Any videotape that has been played frequently will also have added white noise. You already know this if you rented a popular videotape from the local video store back in the days when those stores still offered tapes. Any copy made from that tape is going to have at least as much hiss, even on the day that copy is made. Copying from a digital source, however, is quite different. Remember that the digital copy process does not introduce any white noise, hiss, or snow. The quality of the copy is as good as the original, even if copied many years later.
If you have family videos on VHS tapes, you might think about copying them to DVD disks now!
The life expectancy of all CD and DVD disks depends upon the processes that created the disks and recorded information on them.
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