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Every month or so I get a call from a client about problems that an editor had with their tape. The problem is usually with loading footage into an NLE, with breaks in time code and picture. This occurs most often in BetacamSP camcorders, although other tape formats, which are similar in operation, can have these same problems. 

Camcorders and dockable decks have the ability to make "back space edits". Decks work like this: while recording and the "record" button is hit, the recording stops and the tape backs up a number of frames, then pauses. When you hit the "record" button again, the recording starts at the end of the last recording, with continuous time code, control track and video. Playback in either a linear or non-linear edit systems has no problems.

To work properly, the VTR must remain in standby mode of operation with the video drum spinning. This spinning creates an air-bearing surface with very low friction, which allows for the tape to move quickly enough to begin recording at that exact point it was last paused. Playback of this footage shows no breaks in picture or TC.

Problems with back space edits occur when the camcorder or deck is powered down, tape removed and inserted again as with B-roll swap, or just a battery change. Any time the video drum is stopped, you lose that friction-free tape to drum contact. Now when you go into record or standby again, the drum must turn against the tape with a higher friction. Depending upon the amount of wear on the head drum, the friction varies. This drag caused by the friction moves the tape enough to make the next recording at a slightly different location on tape. The playback of this spot on tape will often show a gap in RF, and time-code signal.

While newer decks have less of a problem here, there is no cost-effective way to keep them new. The drums are very expensive and are only replaced when they begin to make, or are close to making bad recordings.

How do you deal with this issue? You could just leave your camera in standby whenever shooting. This, however, causes additional headwear, greater chance of a head clog, and additional battery consumption. Batteries have to be changed anyway forcing you out of standby mode. You could try hitting review button on lens while in standby mode after either power down or save mode operation. This causes the tape to back-up again and may allow a good camera edit.

Probably the most important practice is to leave at least five seconds of rolled tape before any action takes place. Playback decks need enough time to lock-up their servo systems, to provide for stable picture, sound and accurate time code. This will go along way in making your editors happy.

As an experiment, make a sample tape of power down, save and standby mode camera edits at different parts of the tape, and in different modes of operation. Playback this tape and look for problems. It is better to know before a client gets your tape how your recordings react under such situations. If you find that edits are bad when in standby mode, your deck may be in need for service. Better you find out yourself than have your client tell you.

Another time code issue you could have is when swapping A-roll tapes with B-roll tapes. Some older decks will continue with last recorded time-code, while some newer decks will continue with the last time-code on the tape you just inserted.

One client complained of this problem when operating to an older model. There was no problem, just a difference in time-code operation.

Most decks use time-code memory batteries that keep the time-code free running or maintain the time-code when changing camera batteries. These batteries actually power circuits within the deck anytime the battery is removed, and should be replaced every one to three years depending on model. On the older Sony BVV-5s and early BVW-35s, a very large capacitor was used in place of a battery, which allowed only eight minutes of time-code back-up. They of course fail over time also.

Video gear is extremely complex. Understanding basic operations will help reduce problems and stress in the field.

Take care,
Roger  

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