Be kind, please don't rewind.

Just like ink bleeds through paper, the magnetic field of magnetic tape bleeds through to adjacent layers on a spool. Various factors can change how badly the contents of the tape is affected. Digital signals are generally more robust than analogue ones, extremes in temperature and/or humidity make the tape more susceptible to damage, exposure to an external magnetic field decreases the signal to noise on the tape, and thinner tapes and LPs are inherently more fragile.

Magnetic print-through is generally bad, although it is used in some duplicators due to the speed it allows the tapes to run at. Even in this scenario, print-through is still not the most desirable technique due to the gradual degradation of the master with every pass. Geometry tells us that the bleed on a spool is going to be ever so slightly offset from the original signal, the result is an echo. In the case of audio, we get just that, an echo. In the case of video, particularly VHS, echoes of the chrominance bursts make locking sync difficult necessitating the use of a genlocker, a device that strips and regenerates the video signal's chrominance bursts.

While not eliminating print-through, storing tapes tail-out reduces pre-echo print-through, making the echo less noticeable. The difference between a pre-echo or a post-echo could be the difference between a sync lockable video feed and one that's not. So please be kind to your tapes, don't rewind them.


Sources: Working under people with decades of experience in the industry, and digitising too many VHS tapes.


Written by Scout, 3/12/10. Retroactively published by Scarlet.

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