If you have a collection of old VHS tapes you are still hanging on to, it is important to realize that the memories they hold will not last forever. Signal loss, shedding, and tape wear are common issues that arise as video tapes age. Deterioration of tapes can eventually become so severe that it becomes impossible to view the content stored on them.
Video tape is a form of magnetic tape used for storing video and sound. To be more specific, a video tape consists of magnetic particles, namely metal oxide (i.e. rust), glued to a ribbon of mylar, along with a protective layer of lubricant which helps to protect the tape from the stresses of repeated playback and rewindings.
How long will the magnetic data last on a VCR tape before it becomes no longer u…
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Over time, the VHS lifespan decreases as these different layers begin to break down. Other factors, such as tapes being kept in a humid environment, can cause the tape to delaminate; the glue fails and the metal oxide no longer remains attached to the substrate.
The lifespan between tape formats differs. High-grade tapes tend to be more durable and have greater metal particle density which means a longer shelf life. Cheap tapes that flooded the market in the 1990s were cheap for a reason; flimsy cassette shells, low-density metal oxide, and inferior substrate which translates to shorter shelf lives.
The binder layer comes into direct contact with the heads of the playback machine and provides the signal quality. It contains magnetic particles that store the information on the tape. They are usually suspended in the binder along with lubricant, the purpose of which is to seep out during playback (microscopically), to prevent damage to the binder layer. The substrate and backing layers are there for dimensional stability and strength, and the backing layer also helps to reduce friction.
There are a number of factors that cause VHS tape to degrade, a key one being that the magnetic charge needed for them to work is not permanent. Magnetic particles gradually lose their charge, in a process called remanence decay. The rate of decay will depend on the exact chemistry of the particles used, but if it does happen you can expect some colour shift towards weaker hues and a loss of detail overall in your footage.
The lubricant in the binder layer can be used up; the level of lubricant will decrease with each use. Even if the tape remains unused, the lubricant can evaporate or degrade over time. As it erodes, the binder layer will take on more wear when the tape is played, which could affect the magnetic particles and cause information loss.
Research generally indicates that magnetic tapes like VHS and Hi8, stored well, will experience 10-20% signal loss, purely from magnetic decay, after 10-25 years. Given how long VHS has been obsolete, chances are that your old tapes have already reached, if not exceeded, this time frame.
If CDs can last over 100 years, why is the lifespan of VHS tapes so much shorter? The answer lies in the magnetic charge. Over time, the magnetic particles lose charge in a phenomenon called remanence decay. This causes discoloration, blacked out scenes, and eventually complete loss of footage. The best way to preserve tapes is to store them in a cool and dry place with little to no climate change. But keep in mind even the best quality tapes stored in optimal conditions will succumb to deterioration.
The longevity of the data stored on any drive depends on the conditions where it is stored and for how long. For hard drives, there are three main factors: magnetic field breakdown, environmental conditions, and mechanical failure.
Most sources state that permanent magnets lose their magnetic field strength at a rate of 1% per year. Assuming this is valid, after 69 years, we can assume that half of the sectors in a hard drive would be corrupted (since they all lost half of their strength by this time). Obviously, this is quite a long time, but this risk is easily mitigated - simply re-write the data to the drive. How frequently you need to do this depends on the following two issues (I also go over this in my conclusion).
To periodically refresh the data on the drive, simply transfer it to another location, and re-writing it back to the drive. That way, the magnetic domains in the physical disk surface will be renewed with their original strength (because you just re-wrote the files back to the disk). If you're concerned about filesystem corruption, you can also format the disk before transferring the data back.
Some government organizations "sanitize" hard drives by exposing them to a very powerful magnetic field, effectively (and literally) removing the data from the hard drive by "resetting" all of the sectors. Do note that storing a hard drive in, or near the presence of magnetic fields (alternating or static) will severely impact the data stored on the drive.
Some people mention that they believe that the actual physical motor in the hard drive will fail long before the data on the disk platters degrades significantly. While this is an issue for a hard disk that has been sitting for a long time, if the disk is used once in a while (at least every 3-5 years), this should mitigate this problem.
Compared to conventional long-term storage mediums (tapes, optical discs), the appeal of hard drives is quite apparent - they are small, easy to move around, have very good transfer rates, switch between computers with ease, and the data lasts for a fairly long time. But, like the two other storage mediums I mentioned, hard drives do not come without their own caveats. So long as you periodically "refresh" the data on the hard drive (and, in turn, ensure the mechanical aspects of the drive itself are still functioning), you should have no problems.
The conventional wisdom is that you should revisit your data every five years to make sure that you can still read it. The general consensus is that the magnetic platters in the drive will start to degrade in 5 years of storage. The bigger issue is that storage technology changes. That means a format that works today will be unreadable 5-10 years from now.
It depends entirely on the ambient electromagnetic noise, the density of the media, and the quality of the read/write head. More noise, more dense data, and lower quality read/write mechanisms will result in so-called "bit rot" setting in faster. It's also going to vary depending on the quality of the internal motor and bearings. Part of the problem of spinning up an old disk is the fact that they're mechanical, and mechanical things don't age well without maintenance.
On mag tape, I've always heard the limiting factor is the method they use to bind the magnetic particles to the tape backing. The shelf life in perfect conditions (no light, nitrogen environment, temperature controlled) for that is supposed to be about 25 years (which is a problem for hospitals, who are supposed to maintain data backups for the life of the patient). Tape continues to be used because it is cheap and very high density, not because it has a superior shelf life.
Simply put, however, long term reliability and integrity of hard disk storage is unknown. Even if the magnetic area is still good and has your data intact, corrosion on the read/write heads can cause read or write errors.
If the tape is a T-120 and the VCR is set to SP mode, for example, it will record for two hours with the best visual quality. The LP mode will last 4 hours, while the EP mode will last 6 hours.
VHS tapes last 10 to 25 years. How long will VHS tape last varies and depends on the quality of the tape as well as proper storage. Tapes stored in a climate-controlled environment can last significantly longer than the ones not stored correctly.
Originally, Beta I machines using the NTSC television standard were able to record one hour of programming at their standard tape speed of 1.5 inches per second (ips).[23] The first VHS machines could record for two hours, due to both a slightly slower tape speed (1.31 ips)[23] and significantly longer tape. Betamax's smaller-sized cassette limited the size of the reel of tape, and could not compete with VHS's two-hour capability by extending the tape length.[23] Instead, Sony had to slow the tape down to 0.787 ips (Beta II) in order to achieve two hours of recording in the same cassette size.[23] Sony eventually created a Beta III speed at 0.524ips which allowed NTSC Betamax to break the two-hour limit, but by then VHS had already won the format battle.[23]
There is a clear tape leader at both ends of the tape to provide an optical auto-stop for the VCR transport mechanism. In the VCR, a light source is inserted into the cassette through the circular hole in the center of the underside, and two photodiodes are to the left and right sides of where the tape exits the cassette. When the clear tape reaches one of these, enough light will pass through the tape to the photodiode to trigger the stop function; some VCRs automatically rewind the tape when the trailing end is detected. Early VCRs used an incandescent bulb as the light source: when the bulb failed, the VCR would act as if a tape were present when the machine was empty, or would detect the blown bulb and completely stop functioning. Later designs use an infrared LED, which has a much longer life.[citation needed]
Since the recording/playback time for PAL/SECAM is roughly 1/3 longer than the recording/playback time for NTSC, some tape manufacturers label their cassettes with both T-XXX and E-XXX marks, like T60/E90, T90/E120 and T120/E180.
In the original VHS specification, audio was recorded as baseband in a single linear track, at the upper edge of the tape, similar to how an audio compact cassette operates. The recorded frequency range was dependent on the linear tape speed. For the VHS SP mode, which already uses a lower tape speed than the compact cassette, this resulted in a mediocre frequency response of roughly 100 Hz to 10 kHz for NTSC,[citation needed] frequency response for PAL VHS with its lower standard tape speed was somewhat worse. The signal-to-noise ratio (SNR) was an acceptable 42 dB. Both parameters degraded significantly with VHS's longer play modes, with EP/NTSC frequency response peaking at 4 kHz. S-VHS tapes can give better audio (and video) quality, because the tapes are designed to have almost twice the bandwidth of VHS at the same speed. 2ff7e9595c
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