Why We Didn’t Take Screen Grabs in the 1980s

Opinion

We couldn’t. The operating system on our micro-computers (today known as PCs) was text-based DOS [disk-based operating system], so there were no images to grab. (You could use the DOS '>' redirect function to save screen text to a file, such as dir /s > dir.txt.) So, marketing firms would send out prints and slides of their software to show off the products, in the hope that we magazine editors would use them in their print publications.

A very few programs included a screen grab function. WordPerfect for DOS had one, but saved images in its proprietary WP5 format; this was fine, as long as you were using the images in WordPerfect documents. (Translating between graphical file formats was uncommon.) AutoCAD v1.x for DOS had a screen grabber that sent the image direct to the printer, which was removed in later releases.

In the second half of the 1980s, I was the technical editor of CADalyst magazine, and I had a need to show the screens of AutoCAD, as well as of products that worked with AutoCAD.? Images had to be made physically of the computer screen. I could have purchased an expensive rig that added a hood and a brand-name 35mm SLR camera for taking pictures. But it was expensive.

To get a nice picture, I had to compensate for the problems posed by photographing actual screens of computers. One was glare from the daylight and from office lights; another was the curvature of the computer screen, which in those days were made from cathode ray tubes (CRT); a third problem was setting the correct exposure in the camera to end up with a richly-colored image.

(CRTs formed their images by cleverly using electro-magnets to direct a beam of electrons across the glass, which was coated with phosphorus. The beam was turned on and off about 30 times a second, causing the phosphorus to glow briefly. The beam scanned across horizontally [a scan line], then dropped down a fraction of an inch to scan the next line. The glass was curved so that the electron beam traveled the same distance from its source to the screen, no matter its position on the screen.)

To compensate, I came into the office of CADalyst magazine at night, set up my camera on a tripod with a 100mm lens, reduced the f-stop by -2, and used the self-timer to take the photograph. It took, naturally, me a while to get all these parameters correct, as I was working with slide film, which needed to be sent away for processing. It could take a week or two to see if the results turned out -- or not.

In time, I had my formula for success:

• Night time -- to eliminate glare from office lights and windows
• Tripod and self-timer -- to eliminate shake from the pictures
• 100mm lens -- to minimize the curvature of CRT screens
• Reduce f-stop by 2 -- to keep the image from being over bright, so colors look richer

When Windows came with a built-in screen grabber, it was heaven on earth! For many years now, I have used a older version of WinSnap as my preferred screen grabber, because of its Object mode, which makes it a snap to grab UI elements, like menus and toolbar icons.

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