Questions Beginners Ask
Tom R. Halfhill Staff Editor
Are you thinking about buying a computer for the first time, but don't know much about computers? Or maybe you just purchased a computer and are still a bit baffled. Each month in this column, COMPUTE! will answer some questions often asked by beginners.
Q For keeping programs on tape, what's the best kind of cassette recorder I should buy for my computer?
A First of all, be sure you have an option in this area. Some computers require a special recorder and are not designed to work with ordinary cassette recorders. Examples are Commodore and Atari computers. The Commodore 64, VIC-20, and PETs require a Datassette recorder; the Atari 400/800 and new XL models require the 410 or 1010 Program Recorder. These special recorders are optimized for data storage and generally cannot be used for any other purpose. For instance, neither the Commodore Datassette nor the Atari Program Recorders have microphones or standard input/output phono jacks. Instead, they have interface cables which plug into a special port on the computer.
Other personal computers are designed to work with any standard cassette recorder. Examples are the Texas Instruments TI-99/4A, Radio Shack TRS-80 computers, the Apple II, IBM PC/ PCjr, and Timex/Sinclair computers.
If you have a computer which can work with a standard recorder, check the manuals to see if the manufacturer recommends a certain brand. Sometimes a recommendation means the manufacturer has experimented with different recorders and has found a particular model to be superior. On the other hand, some manufacturers merely recommend a recorder made by an affiliated company. Radio Shack, for instance, advises TRS-80 owners to buy a certain Radio Shack recorder for their computers.
The best way to get a reliable recorder is to try several different models with your computer and decide for yourself. Unfortunately, you probably won't have access to very many recorders, unless you can find a store which will let you return any which don't work well. Perhaps you can borrow cassette recorders from friends for your tests. Or contact your local users group for advice.
Other than the computer manufacturers' own units, we know of only one recorder specifically made for home computers: the General Electric Computer Program Data Recorder (Model 3-5158A). It looks about the same as any other recorder in its price range (under $40), and even has a built-in microphone for taping voice or music. However, GE says the unit has a flatter bass response for more reliable data recording. It also has two features you should look for in any recorder to be used with a computer—a tape counter and a tone control. Tape counters are invaluable for locating programs in the middle of tapes, and tone controls can optimize the recorder's output for your computer. With any recorder, you should experiment to find the exact volume and tone settings that work best and then mark them for future reference.
Q I've tried to take pictures of my computer screen like the ones I've seen in COMPUTE!, but they never come out quite right. What's the best way to do this?
A In the first place, you must have a camera which can focus closely enough to fill the viewfinder with the screen. Most inexpensive cameras cannot focus sharply on objects less than three to five feet away. Inexpensive cameras also have semi-wide-angle lenses which make the image appear even smaller, plus separate view-finders which do not show the actual image as seen by the lens (and therefore the film). At COMPUTE!, all screen photos are taken with a tripod-mounted 35mm single-lens reflex camera with a 50mm (normal) lens. The camera is positioned so the edges of the screen are just visible at the edges of the viewfinder.
With this setup, only three major problems remain: avoiding reflections, determining proper exposure, and eliminating partial scan lines.
Reflections on the glass video screen are distracting and often show up as "hot spots" in the photograph. Flash pictures, of course, are out of the question. All light for the picture must come from the screen. We avoid reflections by shooting the photos in completely darkened, windowless rooms. At home you'll have to shut off all the lights, pull the window shades and curtains, and close the doors. If this isn't practical, try erecting a blanket "tent" over the camera and screen to block off all outside light.
Unfortunately, darkening the room can complicate the second problem—determining proper exposure. If the camera has a built-in meter, it is fooled by the dark background. We often get around this problem with a handheld light meter, holding it close enough to the screen to make sure it isn't reading anything else. You can do the same thing with your camera's meter, although it means removing the camera from the tripod for each reading. And be sure not to read a completely dark or light screen. Take your readings from medium tones or colors.
The camera must be mounted on a tripod for the exposure because of the very slow shutter speeds required. TV sets and monitors display an image by constantly redrawing it on the screen—about every 1/30 second. Theoretically, then, shutter speeds faster than 1/30 second result in a picture with only a partial screen image (the partial image shows up as a dark band across the screen). In practice, we've found that shutter speeds no faster than 1/4 second are necessary to completely eliminate partial scan lines. And that, in turn, means the image must remain motionless for the duration of the exposure to avoid blurs. We often have to modify programs to freeze them on the screen.
Finally, slow- or medium-speed films are better than fast films. We use Kodak Ektachrome 64 (a color slide film) mainly because it can be custom-processed locally in a few hours. Actually we would prefer Kodachrome or another film with a warmer response to compensate for the strong blues emitted by most video tubes. Our exposures with Ektachrome 64 are usually about 1/2 second at f/16. We bracket one stop each way to insure good results. We also hook up the computer to a regular computer monitor instead of an ordinary TV to get a sharper picture.