Home Video Hints: Get Those Tapes in Shape (page 2)

About Blacking a Tape

Blacking a tape means recording its entire length with no video or audio information, resulting in a tape that is, paradoxically, fully recorded and at the same time blank.

There are two reasons for blacking an analog tape. First, playing back the first part of the tape will usually reveal stretched tape, misaligned record heads or similar problems. The screen will show giveaway lines and other artifacts, instead of the expected black. (I once had to redo an entire morning of an expensive professional shoot because a roll of bad tape was not caught before use.)

A more important purpose is to lay down an uninterrupted reference track that always reveals exactly where you are in the tape and how to return to any shot located previously. Whenever you press Record, whether blacking the tape or making a shot, you lay down a reference track along with the picture, sound and sync information.

Digital and hobbyist analog camcorders create two quite different reference tracks. An analog track, called a control track, simply carries a pulse recorded once every second. A camcorder or VCR computes elapsed time on a tape by counting and adding these pulses. It is important to note that these counter numbers are not recorded onto the tape and will reset at zero each time a tape is ejected or inserted. In an analog system, the playback time-counter will stop when it has no more pulses left to count.

A digital camcorder, by contrast, uses time code to assign a unique address to every video frame. In a digital system, the recorder will start assigning time code from zero when it finds a codeless (blank) section of tape. This can result in duplicate time code numbers on a single tape and would make tape logging difficult, and computer editors could find batch capture operations do not work. It is a bit of a myth, however, that DV camcorders perform insert edits when recording, leaving existing time code untouched on the tape. It may appear that this is true, since the new time code exactly matches the time code that is over-written.

In both systems, the solution to these problems is to lay down an uninterrupted reference track before shooting any video by blacking the tape, thus guaranteeing continuous numb…