Adam Lott is a second year MSI student specializing in Archives and Records Management with an interest in moving-image media. He is the latest participant in The Archivists Apprentice series, which follows School of Information students as they complete their internships. You can read his previous posts here.
Cutting Through the Magnetic Tape, Part 2
A common mantra for archivists is “know thy collection.” This is a relevant practice for any archive, however, when dealing with time-based media there should really be an addendum: “Know thy equipment.” Between U-Matic, Betamax, Digibeta, DV Cam, the occasional film reel, and every format in between, appropriate players must be secured, lest you desire a collection of useless plastic. Unfortunately, obtaining this equipment can be a chore in itself. Take the U-Matic tape deck, for instance. What I’ve learned is that these decks are always breaking, are incredibly expensive to replace, and are becoming more and more difficult to come by.
Among the very first things I learned at CUNY was how to properly clean the heads of a helical scanning deck. Saying that alone was confusing in itself, but after delving into the inner workings of the deck, everything soon became clear. As a space saving technique, sound and video data is written onto a tape diagonally, and must be read as such. A cylindrical “drum” is at the center of every tape deck and is equipped with two “heads” which read a tape’s encoded data. By rotating past the tape, one head reads every odd line, while the other reads every even line.
To better understand what I mean by “lines,” observe the picture of the plane. Notice how the image is spliced into black and colored lines. Now imagine these lines as the even and odd lines being read by the cylinder heads. This is why we call VHS interlaced, because it displays many lines representing one solid image. North American standards dictate that an upwards of 500 lines make up a single frame of an image, with 29.97 frames occurring every second. With so many moving parts, it’s easy to see how a lot can go wrong.
When digitizing video, it’s important to be cognizant of the condition of your equipment. Frequently, problems within the deck can be identified based off of errors present in recorded video. For instance, the infamous “tracking error” occurs when the drum heads aren’t in synch with the moving tape, causing image distortion. Other issues can occur from dirty heads, poor tape tension, scratches on your tape, and an endless array of other factors. Once your image looks good, color hue and intensity must be adjusted using a vectorscope and waveform monitor. These are used in tandem with a color test pattern. To quickly sum up this process, think of the test bars as a palette for the colors displayed on a TV screen. By representing this palette on a waveform monitor and vectorscope, you can tell if a certain color is too bright, too dark, or too dominant, and adjust to a proper setting.
In the end though, many decks are insufficient for use and must be discarded outright. In cases like these, we salvage as many parts as possible and send them on their way. Having spent significant time with these machines, it was disheartening seeing them go, especially when you consider that they were once sold for $30,000 per deck. As with anything, the fragility of video cassettes and their players scale with their age, and securing the appropriate tools for digitization is becoming increasingly difficult. The more acquainted I become with video equipment the better prepared I feel to address these challenges in the future. Ensuring their longevity is essential for ensuring the longevity of your assets.