DV Info Net - Different makes of tape?

Quote:

Originally Posted by Sherman Bahr (Post 1800206)

Someone once told me that the higher the grade of tape the less that it wants to rearrange itself after it's been written to. This was told to me back in the VHS days. My assumptions are that the mini DV tape has extremely fine metal particles. Again the finer the particles and the higher the concentration the less that they want to rearrange because they're adhering the magnetic information so tightly. In practice I'm not so sure how true this is.

The one thing that I do know and have experienced is that rewriting over recorded information will cause more tape dropouts. Today's camcorders do a very good job at tape dropout compensation. But obviously there are times where the dropout is too severe to be covered up and that's when you see it.....

'Normal' tapes from reputable manufacturers have the same magnetic material compositions as 'professional' products. Most of the difference is the quality of the case and as has been said, the medium's freedom from stretches and uneven coating, as would be experienced from the edge of the manufactured roll. Once the product is packaged, the situation is different for each tape transport. A really bad one will cause coating shedding at a faster rate than a well set up one with little wear. Assuming that we aren't talking about the continued use of faulty mechanisms, even a well used drive will probably give little trouble with tens of tape passes. It's irrelevant how many times the passes involve erasure and re-recording, the mechanical stress is the same and the magnetic properties do not diminish with changes of their state. If that was the case, hard drives would be useless after a few hours use as the materials have similar magnetic durability.
As far as magnetic pattern retention is concerned, digital tape has little of the problems that we lived with in analogue tape use. The tape does not need to have linear magnetic properties, so it is designed for maximum coercitivity and only the field at the erase and record heads will move any underlying patterns. Of course, if the heads are faulty or worn out, they won't perform properly but we are considering equipment that is functioning within its normal parameters.
A tape will shed much more coating on its first pass than on the succeeding passes until it is nearing the end of its life. That life should be many passes downstream even for consumer tapes, whether they are still being used to play the first recording made on them or the last of a succession of writes.